IEC 61558-2-3:2023

IEC 61558-2-3 EXV ®
Edition 3.0 2023-06
EXTENDED VERSION
INTERNATIONAL
STANDARD
colour
inside
This extended version of IEC 61558-2-3:2023 includes the content of the references made to
IEC 61558-1:2017
GROUP SAFETY PUBLICATION
Safety of transformers, reactors, power supply units and combinations thereof –
Part 2-3: Particular requirements and tests for ignition transformers for gas and
oil burners
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
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IEC Secretariat Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.
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IEC 61558-2-3 EXV ®
Edition 3.0 2023-06
EXTENDED VERSION
INTERNATIONAL
STANDARD
colour
inside
This extended version of IEC 61558-2-3:2023 includes the content of the references made to
IEC 61558-1:2017
GROUP SAFETY PUBLICATION
Safety of transformers, reactors, power supply units and combinations thereof –
Part 2-3: Particular requirements and tests for ignition transformers for gas and
oil burners
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.180 ISBN 978-2-8322-7162-9
– 2 – IEC 61558-2-3:2023 EXV  IEC 2023
CONTENTS
FOREWORD . 9
INTRODUCTION TO IEC 61558-1:2017 . 12
INTRODUCTION . 15
1 Scope . 16
2 Normative references . 17
3 Terms and definitions . 20
3.1 Transformers . 20
3.2 General terms . 24
3.3 Operations and protections . 25
3.4 Circuits and windings . 27
3.5 Ratings . 28
3.6 No-load values . 30
3.7 Insulation . 30
3.8 Touch current and protective earthing conductor current . 34
4 General requirements . 34
5 General notes on tests . 35
6 Ratings . 37
7 Classification . 38
8 Marking and other information . 39
9 Protection against electric shock . 45
9.1 General . 45
9.2 Protection against contact with hazardous-live-parts . 45
9.2.1 Determination of hazardous-live-parts . 45
9.2.2 Accessibility to hazardous-live-parts . 46
9.2.3 Accessibility to non hazardous-live-part . 49
9.3 Protection against hazardous electrical discharge . 49
10 Change of input voltage setting . 49
11 Output voltage and output current . 50
12 No-load output voltage . 51
13 Short-circuit voltage . 51
14 Heating . 51
14.1 General requirements . 51
14.1.1 Temperature-rise test . 51
14.1.2 Alternative temperature-rise test . 53
14.1.3 Determination of steady-state conditions . 56
14.2 Application of 14.1 or 14.3 according to the insulation system. 58
14.3 Accelerated ageing test for undeclared class of insulation system . 58
14.3.1 General . 58
14.3.2 Heat run . 59
14.3.3 Vibration . 59
14.3.4 Moisture treatment . 59
14.3.5 Measurements . 59
15 Short circuit and overload protection. 60
15.1 General requirements . 60
15.1.1 Short circuit and overload test method . 60

15.1.2 Alternative short circuit and overload test method . 62
15.2 Inherently short-circuit proof transformers . 62
15.3 Non-inherently short-circuit proof transformers. 62
15.4 Non-short-circuit proof transformers . 64
15.5 Fail-safe transformers . 64
16 Mechanical strength . 65
16.1 General . 65
16.2 Stationary transformers . 65
16.3 Portable transformers (except portable transformers with integral pins for
introduction in socket-outlet in the fixed wiring) . 65
16.4 Portable transformers provided with integral pins for introduction in socket-
outlets of the fixed wiring . 66
16.4.1 General requirements . 66
16.4.2 Portable transformers provided with integral pins according to EN
50075 (IEC plug type C) for introduction in socket-outlets of the fixed
wiring . 67
16.5 Additional requirements for transformers to be used in vehicles and railway
applications . 68
16.5.1 Transformers to be used in vehicles and railway applications . 68
16.5.2 Test requirements for the transportation of transformers . 69
17 Protection against harmful ingress of dust, solid objects and moisture . 69
17.1 Degrees of protection provided by enclosures (IP code) . 69
17.1.1 General requirements . 69
17.1.2 Tests on transformers with enclosure . 71
17.2 Humidity treatment . 73
18 Insulation resistance, dielectric strength and leakage current . 74
18.1 General . 74
18.2 Insulation resistance . 74
18.3 Dielectric strength test . 74
18.4 Insulation between and within windings . 75
18.5 Touch current and protective earthing conductor current . 75
18.5.1 General . 75
18.5.2 Touch current . 76
18.5.3 Protective earthing conductor current . 77
19 Construction . 77
19.1 General construction . 77
19.2 Flammability of materials . 78
19.3 Short-circuit characteristics of portable transformers . 78
19.4 Class II transformer contact prevention of accessible conductive parts . 78
19.5 Class II transformer insulation reassembling after service . 78
19.6 Loosening of wires, screws or similar parts . 79
19.7 Resistor or capacitor connection with accessible conductive parts . 79
19.8 Bridging of separated conductive parts by resistors or capacitors . 79
19.9 Insulating material separating input and output windings . 80
19.10 Accidental contact protection against hazardous-live-parts provided by
isolating coating . 80
19.11 Insulating material of handles, operating levers, knobs and similar parts. 81
19.12 Winding construction . 82
19.13 Fixing of handles, operating levers and similar parts . 86
19.14 Fixing of covers providing protection against electric shock . 86

– 4 – IEC 61558-2-3:2023 EXV  IEC 2023
19.15 Strain on fixed socket-outlets caused by pin-transformers connection . 86
19.16 Portable transformers for use in irregular or harsh conditions . 86
19.17 Drain hole of transformers protected against ingress of water . 86
19.18 Plug connected transformers protected against ingress of water . 86
19.19 Flexible cable or flexible cord connection for class I portable transformers . 86
19.20 SELV- and PELV-circuit separation of live parts . 87
19.21 Protection against contact for FELV-circuit. 87
19.22 Protective earthing regarding class II transformers . 88
19.23 Protective earthing regarding class III transformers . 88
20 Components . 88
21 Internal wiring . 93
22 Supply connection and other external flexible cables or cords . 94
23 Terminals for external conductors . 100
24 Provisions for protective earthing. 102
25 Screws and connections . 103
26 Creepage distances, clearances and distances through insulation . 106
26.1 General . 106
26.2 Creepage distances and clearances . 107
26.2.1 General . 107
26.2.2 Windings covered with adhesive tape . 107
26.2.3 Uncemented insulationing parts . 107
26.2.4 Cemented insulating parts . 107
26.2.5 Enclosed parts (e.g. by impregnation or potting) . 108
26.3 Distance through insulation . 109
27 Resistance to heat, fire and tracking . 121
27.1 General . 121
27.2 Resistance to heat . 121
27.3 Resistance to abnormal heat under fault conditions . 121
27.4 Resistance to fire . 121
27.4.1 General . 121
27.4.2 External accessible parts . 121
27.4.3 Internal parts . 122
27.5 Resistance to tracking . 122
28 Resistance to rusting . 122
Annex A (normative) Measurement of creepage distances and clearances. 124
Annex B (normative) Testing a series of transformers . 128
B.1 General . 128
B.2 Requirements . 128
B.3 Constructional inspection . 129
Annex C (void) . 130
Annex D (void) . 131
Annex E (normative) Glow-wire test . 132
E.1 General . 132
E.2 Severity . 132
E.3 Conditioning . 132
E.4 Test procedure . 132

Annex F (normative) Requirements for manually operated switches which are parts of
transformers assembly . 133
F.1 General . 133
F.2 Switches tested as a separate component . 133
F.3 Switches tested as part of the transformer . 133
Annex G (normative) Tracking test . 136
G.1 General . 136
G.2 Test specimen . 136
G.3 Test apparatus . 136
G.4 Procedure . 136
Annex H (normative) Electronic circuits . 137
H.1 General . 137
H.2 General notes on tests (addition to Clause 5). 137
H.3 Short circuit and overload protection (addition to Clause 15) . 137
H.4 Creepage distances, clearances and distances through insulation (addition
to Clause 26) . 139
Annex I (informative) Dimensions for rectangular cross-section connectors of
transformers, basic dimensions and coordination . 141
Annex J (normative) Measuring network for touch-currents . 144
Annex K (normative) Insulated winding wires . 145
K.1 General . 145
K.2 Type tests . 145
K.2.1 General . 145
K.2.2 Dielectric strength test . 145
K.2.3 Flexibility and adherence . 145
K.2.4 Heat shock . 146
K.2.5 Retention of dielectric strength after bending . 146
K.3 Testing during manufacturing . 147
K.3.1 General . 147
K.3.2 Routine test . 147
K.3.3 Sampling test . 147
Annex L (normative) Routine tests (production tests) . 148
L.1 General . 148
L.2 Protective earthing continuity test . 148
L.3 Checking of no-load output voltage . 148
L.4 Dielectric strength test . 148
L.5 Checking of protective devices mounting . 149
L.6 Visual inspection . 149
L.7 Repetition test after routine dielectric strength test . 149
Annex M (informative) Examples to be used as a guide for 19.1 . 150
M.1 General . 150
M.2 Coil-former . 150
M.2.1 Concentric type . 150
M.2.2 Side-by-side type . 151
M.3 Windings . 151
M.3.1 Without screen . 151
M.3.2 With screen . 152
Annex N (informative) Examples for checking points of dielectric strength test voltages . 153

– 6 – IEC 61558-2-3:2023 EXV  IEC 2023
Annex O (void) . 155
Annex P (informative) Examples for measurement points of creepage distances and
clearances . 156
Annex Q (informative) Explanation of IP numbers for degrees of protection . 159
Q.1 General . 159
Q.2 Degrees of protection against access to hazardous parts and against solid
foreign objects . 159
Q.3 Degrees of protection against ingress of water . 161
Annex R (normative) Explanations of the application of 6.1.2.2.1 of IEC 60664-1:2007 . 162
R.1 Impulse dielectric test . 162
R.2 Example. 162
Annex S (void) . 164
Annex T (void) . 165
Annex U (void) . 166
Annex V (informative) Symbols to be used for thermal cut-outs . 167
V.1 General . 167
V.2 Non-self-resetting thermal cut-out (see 3.3.4) . 167
V.3 Self-resetting thermal cut-out (see 3.3.3) . 167
Annex W (normative) Coated printed circuit boards . 168
W.1 Preamble . 168
W.2 General . 168
W.3 Cold . 168
W.4 Rapid change of temperature . 168
W.5 Additional tests . 168
Bibliography . 169
Index of defined terms . 171

Figure 1 – IEC 61558 principle . 13
Figure 2 – Mounting box for flush-type transformer . 37
Figure 3 – Test pin (see IEC 61032, test probe 13) . 47
Figure 4 – Standard test finger (see IEC 61032, test probe B) . 48
Figure 5 – Example of back-to-back method – Single phase . 55
Figure 6 – Example of back-to-back method – Three phase . 56
Figure 7 – Amplitude spectrum density for random testing . 68
Figure 8 – Normalised spectrum of shock . 69
Figure 10 – Test configuration: single-phase equipment on star TN or TT system . 77
Figure 11 – Abrasion resistance test for insulating coated layers . 81
Figure 12 – Flexing test apparatus . 98
Figure 13 – Test arrangement for checking mechanical withstanding of insulating
materials in thin sheet layers . 112
Figure 101 – Arcing horn . 123
Figure A.1 – Example 1. 124
Figure A.2 – Example 2. 125
Figure A.3 – Example 3. 125
Figure A.4 – Example 4. 125
Figure A.5 – Example 5. 126

Figure A.6 – Example 6. 126
Figure A.7 – Example 7. 127
Figure A.8 – Example 8. 127
Figure H.1 – Example of an electronic circuit with low-power points . 140
Figure J.1 – Measuring network for touch-current . 144
Figure M.1 – Examples for concentric type constructions . 150
Figure M.2 – Examples for side-by-side type constructions . 151
Figure M.3 – Examples for winding constructions without screen . 151
Figure M.4 – Examples for wrapped winding constructions . 152
Figure M.5 – Examples for winding constructions with screen . 152
Figure N.1 – Transformer of class I construction with metal enclosure . 153
Figure N.2 – Transformer of class II construction with metal enclosure . 154
Figure N.3 – Transformer of class II construction with enclosure of insulating material . 154
Figure P.1 – Transformer of class I construction . 156
Figure P.2 – Transformer of class I construction with earthed metal screen . 157
Figure P.3 – Transformer of class II construction with metal enclosure . 157
Figure P.4 – Transformer of class II construction with enclosure of insulating material . 158
Figure V.1 – Restored by manual operation . 167
Figure V.2 – Restored by disconnection of the supply . 167
Figure V.3 – Thermal link (see 3.3.5) . 167
Figure V.4 – Self-resetting thermal cut-out . 167

Table 1 – Symbols used on equipment or in instructions . 42
Table 101 – Symbols indicating the kind of transformer . 43
Table 102 – Preferred values of operational parameters . 51
Table 2 – Values of maximum temperatures in normal use . 57
Table 3 – Explanation of the maximum winding temperatures required in Table 2 . 58
Table 4 – Test temperature and testing time (in days) per cycle . 59
Table 5 – Maximum values of temperatures under short-circuit or overload conditions . 61
Table 103 – Test time for short-circuit test . 62
Table 6 – Values of T and k for fuses . 63
Table 7 – Pull force on pins . 67
Table 8 – Conditions for vibration testing (random) . 68
Table 9 – Amplitude spectrum density ASD values for accelerated life testing . 68
Table 10 – Frequency values depending on the weight of the specimen . 68
Table 11 – Excitation values for vibration testing . 69
Table 12 – Solid-object-proof transformer test . 71
Table 13 – Values of insulation resistance . 74
Table 14 – Table of dielectric strength test voltages. 75
Table 15 – Limits for currents . 77
Table 16 – Nominal cross-sectional areas of external flexible cables or cords . 95
Table 17 – Pull and torque to be applied to external flexible cables or cords fixed to
stationary and portable transformers . 99

– 8 – IEC 61558-2-3:2023 EXV  IEC 2023
Table 18 – Torque to be applied to screws and connections . 104
Table 19 – Torque test on glands . 106
Table 20 – Clearances in mm . 114
Table 21 – Creepage distances in mm . 115
Table 22 – Distance through insulation in mm . 116
Table 23 – Creepage distances and clearance between terminals for external
connection . 117
Table 104 – Creepage distances and clearances for output terminals . 117
Table 24 – Values of FIW wires with minimum overall diameter and minimum test
voltages according to the total enamel increase . 119
Table A.1 – Width of groove values depending on the pollution degree . 124
Table F.1 – Peak surge current of additional loads. 134
Table I.1 – Dimensions of rectangular copper connectors . 142
Table K.1 – Mandrel diameter . 146
Table K.2 – Oven temperature . 146
Table Q.1 – Degrees of protection against access to hazardous parts indicated by the
first characteristic numeral . 160
Table Q.2 – Degrees of protection against solid foreign objects indicated by the first
characteristic numeral . 160
Table Q.3 – Degrees of protection indicated by the second characteristic numeral . 161
Table R.1 – Impulse test voltage according to 6.1.2.2.1 of IEC 60664-1:2007 . 162

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF TRANSFORMERS, REACTORS,
POWER SUPPLY UNITS AND COMBINATIONS THEREOF –

Part 2-3: Particular requirements and tests for ignition
transformers for gas and oil burners

FOREWORD
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all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
This extended version (EXV) of the official IEC Standard provides the user with the
comprehensive content of the Standard.
made to IEC 61558-1:2017.
The specific content of IEC 61558-2-3:2023 is displayed on a blue background.

– 10 – IEC 61558-2-3:2023 EXV  IEC 2023
International standard IEC 61558-2-3 has been prepared by IEC technical committee 96:
Transformers, reactors, power supply units and combinations thereof. It is an International
Standard.
This third edition cancels and replaces the second edition published in 2010. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) adjustment of structure and references in accordance with IEC 61558-1:2017.
The text of this International Standard is based on the following documents:
Draft Report on voting
96/577/FDIS 96/580/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement,
available at www.iec.ch/members_experts/refdocs. The main document types developed by
IEC are described in greater detail at www.iec.ch/publications.
It has the status of a group safety publication in accordance with IEC Guide 104.
This International Standard is to be used in conjunction with IEC 61558-1:2017.
This document supplements or modifies the corresponding clauses in IEC 61558-1:2017, so
as to convert that publication into the IEC standard: Particular requirements and tests for
ignition transformers for gas and oil burners.
A list of all parts in the IEC 61558 series published under the general title Safety of
transformers, reactors, power supply units and combinations thereof, can be found on the
IEC website.
Future standards in this series will carry the new general title as cited above. Titles of existing
standards in this series will be updated at the time of the next edition.
Where this document states "addition", "modification" or "replacement", the relevant te
...

IEC 61558-2-3 EXV ®
Edition 3.0 2023-06
EXTENDED VERSION
INTERNATIONAL
STANDARD
colour
inside
This extended version of IEC 61558-2-3:2023 includes the content of the references made to
IEC 61558-1:2017
GROUP SAFETY PUBLICATION
Safety of transformers, reactors, power supply units and combinations thereof –
Part 2-3: Particular requirements and tests for ignition transformers for gas and
oil burners
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.
IEC Secretariat Tel.: +41 22 919 02 11
3, rue de Varembé info@iec.ch
CH-1211 Geneva 20 www.iec.ch
Switzerland
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.
About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigendum or an amendment might have been published.
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Stay up to date on all new IEC publications. Just Published
containing more than 22 300 terminological entries in English
details all new publications released. Available online and once
and French, with equivalent terms in 19 additional languages.
a month by email.
Also known as the International Electrotechnical Vocabulary
(IEV) online.
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If you wish to give us your feedback on this publication or need
further assistance, please contact the Customer Service
Centre: sales@iec.ch.
IEC 61558-2-3 EXV ®
Edition 3.0 2023-06
EXTENDED VERSION
INTERNATIONAL
STANDARD
colour
inside
This extended version of IEC 61558-2-3:2023 includes the content of the references made to
IEC 61558-1:2017
GROUP SAFETY PUBLICATION
Safety of transformers, reactors, power supply units and combinations thereof –
Part 2-3: Particular requirements and tests for ignition transformers for gas and
oil burners
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.180 ISBN 978-2-8322-7162-9
– 2 – IEC 61558-2-3:2023 EXV  IEC 2023
CONTENTS
FOREWORD . 9
INTRODUCTION TO IEC 61558-1:2017 . 12
INTRODUCTION . 15
1 Scope . 16
2 Normative references . 17
3 Terms and definitions . 20
3.1 Transformers . 20
3.2 General terms . 24
3.3 Operations and protections . 25
3.4 Circuits and windings . 27
3.5 Ratings . 28
3.6 No-load values . 30
3.7 Insulation . 30
3.8 Touch current and protective earthing conductor current . 34
4 General requirements . 34
5 General notes on tests . 35
6 Ratings . 37
7 Classification . 38
8 Marking and other information . 39
9 Protection against electric shock . 45
9.1 General . 45
9.2 Protection against contact with hazardous-live-parts . 45
9.2.1 Determination of hazardous-live-parts . 45
9.2.2 Accessibility to hazardous-live-parts . 46
9.2.3 Accessibility to non hazardous-live-part . 49
9.3 Protection against hazardous electrical discharge . 49
10 Change of input voltage setting . 49
11 Output voltage and output current . 50
12 No-load output voltage . 51
13 Short-circuit voltage . 51
14 Heating . 51
14.1 General requirements . 51
14.1.1 Temperature-rise test . 51
14.1.2 Alternative temperature-rise test . 53
14.1.3 Determination of steady-state conditions . 56
14.2 Application of 14.1 or 14.3 according to the insulation system. 58
14.3 Accelerated ageing test for undeclared class of insulation system . 58
14.3.1 General . 58
14.3.2 Heat run . 59
14.3.3 Vibration . 59
14.3.4 Moisture treatment . 59
14.3.5 Measurements . 59
15 Short circuit and overload protection. 60
15.1 General requirements . 60
15.1.1 Short circuit and overload test method . 60

15.1.2 Alternative short circuit and overload test method . 62
15.2 Inherently short-circuit proof transformers . 62
15.3 Non-inherently short-circuit proof transformers. 62
15.4 Non-short-circuit proof transformers . 64
15.5 Fail-safe transformers . 64
16 Mechanical strength . 65
16.1 General . 65
16.2 Stationary transformers . 65
16.3 Portable transformers (except portable transformers with integral pins for
introduction in socket-outlet in the fixed wiring) . 65
16.4 Portable transformers provided with integral pins for introduction in socket-
outlets of the fixed wiring . 66
16.4.1 General requirements . 66
16.4.2 Portable transformers provided with integral pins according to EN
50075 (IEC plug type C) for introduction in socket-outlets of the fixed
wiring . 67
16.5 Additional requirements for transformers to be used in vehicles and railway
applications . 68
16.5.1 Transformers to be used in vehicles and railway applications . 68
16.5.2 Test requirements for the transportation of transformers . 69
17 Protection against harmful ingress of dust, solid objects and moisture . 69
17.1 Degrees of protection provided by enclosures (IP code) . 69
17.1.1 General requirements . 69
17.1.2 Tests on transformers with enclosure . 71
17.2 Humidity treatment . 73
18 Insulation resistance, dielectric strength and leakage current . 74
18.1 General . 74
18.2 Insulation resistance . 74
18.3 Dielectric strength test . 74
18.4 Insulation between and within windings . 75
18.5 Touch current and protective earthing conductor current . 75
18.5.1 General . 75
18.5.2 Touch current . 76
18.5.3 Protective earthing conductor current . 77
19 Construction . 77
19.1 General construction . 77
19.2 Flammability of materials . 78
19.3 Short-circuit characteristics of portable transformers . 78
19.4 Class II transformer contact prevention of accessible conductive parts . 78
19.5 Class II transformer insulation reassembling after service . 78
19.6 Loosening of wires, screws or similar parts . 79
19.7 Resistor or capacitor connection with accessible conductive parts . 79
19.8 Bridging of separated conductive parts by resistors or capacitors . 79
19.9 Insulating material separating input and output windings . 80
19.10 Accidental contact protection against hazardous-live-parts provided by
isolating coating . 80
19.11 Insulating material of handles, operating levers, knobs and similar parts. 81
19.12 Winding construction . 82
19.13 Fixing of handles, operating levers and similar parts . 86
19.14 Fixing of covers providing protection against electric shock . 86

– 4 – IEC 61558-2-3:2023 EXV  IEC 2023
19.15 Strain on fixed socket-outlets caused by pin-transformers connection . 86
19.16 Portable transformers for use in irregular or harsh conditions . 86
19.17 Drain hole of transformers protected against ingress of water . 86
19.18 Plug connected transformers protected against ingress of water . 86
19.19 Flexible cable or flexible cord connection for class I portable transformers . 86
19.20 SELV- and PELV-circuit separation of live parts . 87
19.21 Protection against contact for FELV-circuit. 87
19.22 Protective earthing regarding class II transformers . 88
19.23 Protective earthing regarding class III transformers . 88
20 Components . 88
21 Internal wiring . 93
22 Supply connection and other external flexible cables or cords . 94
23 Terminals for external conductors . 100
24 Provisions for protective earthing. 102
25 Screws and connections . 103
26 Creepage distances, clearances and distances through insulation . 106
26.1 General . 106
26.2 Creepage distances and clearances . 107
26.2.1 General . 107
26.2.2 Windings covered with adhesive tape . 107
26.2.3 Uncemented insulationing parts . 107
26.2.4 Cemented insulating parts . 107
26.2.5 Enclosed parts (e.g. by impregnation or potting) . 108
26.3 Distance through insulation . 109
27 Resistance to heat, fire and tracking . 121
27.1 General . 121
27.3 Resistance to abnormal heat under fault conditions . 121
27.4 Resistance to fire . 121
27.4.1 General . 121
27.4.2 External accessible parts . 121
27.4.3 Internal parts . 122
27.5 Resistance to tracking . 122
28 Resistance to rusting . 122
Annex A (normative) Measurement of creepage distances and clearances. 124
Annex B (normative) Testing a series of transformers . 128
B.1 General . 128
B.2 Requirements . 128
B.3 Constructional inspection . 129
Annex C (void) . 130
Annex D (void) . 131
Annex E (normative) Glow-wire test . 132
E.1 General . 132
E.2 Severity . 132
E.3 Conditioning . 132
E.4 Test procedure . 132
Annex F (normative) Requirements for manually operated switches which are parts of
transformers assembly . 133

F.1 General . 133
F.2 Switches tested as a separate component . 133
F.3 Switches tested as part of the transformer . 133
Annex G (normative) Tracking test . 136
G.1 General . 136
G.2 Test specimen . 136
G.3 Test apparatus . 136
G.4 Procedure . 136
Annex H (normative) Electronic circuits . 137
H.1 General . 137
H.2 General notes on tests (addition to Clause 5). 137
H.3 Short circuit and overload protection (addition to Clause 15) . 137
H.4 Creepage distances, clearances and distances through insulation (addition
to Clause 26) . 139
Annex I (informative) Dimensions for rectangular cross-section connectors of
transformers, basic dimensions and coordination . 141
Annex J (normative) Measuring network for touch-currents . 144
Annex K (normative) Insulated winding wires . 145
K.1 General . 145
K.2 Type tests . 145
K.2.1 General . 145
K.2.2 Dielectric strength test . 145
K.2.3 Flexibility and adherence . 145
K.2.4 Heat shock . 146
K.2.5 Retention of dielectric strength after bending . 146
K.3 Testing during manufacturing . 147
K.3.1 General . 147
K.3.2 Routine test . 147
K.3.3 Sampling test . 147
Annex L (normative) Routine tests (production tests) . 148
L.1 General . 148
L.2 Protective earthing continuity test . 148
L.3 Checking of no-load output voltage . 148
L.4 Dielectric strength test . 148
L.5 Checking of protective devices mounting . 149
L.6 Visual inspection . 149
L.7 Repetition test after routine dielectric strength test . 149
Annex M (informative) Examples to be used as a guide for 19.1 . 150
M.1 General . 150
M.2 Coil-former . 150
M.2.1 Concentric type . 150
M.2.2 Side-by-side type . 151
M.3 Windings . 151
M.3.1 Without screen . 151
M.3.2 With screen . 152
Annex N (informative) Examples for checking points of dielectric strength test voltages . 153
Annex O (void) . 155

– 6 – IEC 61558-2-3:2023 EXV  IEC 2023
Annex P (informative) Examples for measurement points of creepage distances and
clearances . 156
Annex Q (informative) Explanation of IP numbers for degrees of protection . 159
Q.1 General . 159
Q.2 Degrees of protection against access to hazardous parts and against solid
foreign objects . 159
Q.3 Degrees of protection against ingress of water . 161
Annex R (normative) Explanations of the application of 6.1.2.2.1 of IEC 60664-1:2007 . 162
R.1 Impulse dielectric test . 162
R.2 Example. 162
Annex S (void) . 164
Annex T (void) . 165
Annex U (void) . 166
Annex V (informative) Symbols to be used for thermal cut-outs . 167
V.1 General . 167
V.2 Non-self-resetting thermal cut-out (see 3.3.4) . 167
V.3 Self-resetting thermal cut-out (see 3.3.3) . 167
Annex W (normative) Coated printed circuit boards . 168
W.1 Preamble . 168
W.2 General . 168
W.3 Cold . 168
W.4 Rapid change of temperature . 168
W.5 Additional tests . 168
Bibliography . 169
Index of defined terms . 171

Figure 1 – IEC 61558 principle . 13
Figure 2 – Mounting box for flush-type transformer . 37
Figure 3 – Test pin (see IEC 61032, test probe 13) . 47
Figure 4 – Standard test finger (see IEC 61032, test probe B) . 48
Figure 5 – Example of back-to-back method – Single phase . 55
Figure 6 – Example of back-to-back method – Three phase . 56
Figure 7 – Amplitude spectrum density for random testing . 68
Figure 8 – Normalised spectrum of shock . 69
Figure 10 – Test configuration: single-phase equipment on star TN or TT system . 77
Figure 11 – Abrasion resistance test for insulating coated layers . 81
Figure 12 – Flexing test apparatus . 98
Figure 13 – Test arrangement for checking mechanical withstanding of insulating
materials in thin sheet layers . 112
Figure 101 – Arcing horn . 123
Figure A.1 – Example 1. 124
Figure A.2 – Example 2. 125
Figure A.3 – Example 3. 125
Figure A.4 – Example 4. 125
Figure A.5 – Example 5. 126
Figure A.6 – Example 6. 126

Figure A.7 – Example 7. 127
Figure A.8 – Example 8. 127
Figure H.1 – Example of an electronic circuit with low-power points . 140
Figure J.1 – Measuring network for touch-current . 144
Figure M.1 – Examples for concentric type constructions . 150
Figure M.2 – Examples for side-by-side type constructions . 151
Figure M.3 – Examples for winding constructions without screen . 151
Figure M.4 – Examples for wrapped winding constructions . 152
Figure M.5 – Examples for winding constructions with screen . 152
Figure N.1 – Transformer of class I construction with metal enclosure . 153
Figure N.2 – Transformer of class II construction with metal enclosure . 154
Figure N.3 – Transformer of class II construction with enclosure of insulating material . 154
Figure P.1 – Transformer of class I construction . 156
Figure P.2 – Transformer of class I construction with earthed metal screen . 157
Figure P.3 – Transformer of class II construction with metal enclosure . 157
Figure P.4 – Transformer of class II construction with enclosure of insulating material . 158
Figure V.1 – Restored by manual operation . 167
Figure V.2 – Restored by disconnection of the supply . 167
Figure V.3 – Thermal link (see 3.3.5) . 167
Figure V.4 – Self-resetting thermal cut-out . 167

Table 1 – Symbols used on equipment or in instructions . 42
Table 101 – Symbols indicating the kind of transformer . 43
Table 102 – Preferred values of operational parameters . 51
Table 2 – Values of maximum temperatures in normal use . 57
Table 3 – Explanation of the maximum winding temperatures required in Table 2 . 58
Table 4 – Test temperature and testing time (in days) per cycle . 59
Table 5 – Maximum values of temperatures under short-circuit or overload conditions . 61
Table 103 – Test time for short-circuit test . 62
Table 6 – Values of T and k for fuses . 63
Table 7 – Pull force on pins . 67
Table 8 – Conditions for vibration testing (random) . 68
Table 9 – Amplitude spectrum density ASD values for accelerated life testing . 68
Table 10 – Frequency values depending on the weight of the specimen . 68
Table 11 – Excitation values for vibration testing . 69
Table 12 – Solid-object-proof transformer test . 71
Table 13 – Values of insulation resistance . 74
Table 14 – Table of dielectric strength test voltages. 75
Table 15 – Limits for currents . 77
Table 16 – Nominal cross-sectional areas of external flexible cables or cords . 95
Table 17 – Pull and torque to be applied to external flexible cables or cords fixed to
stationary and portable transformers . 99
Table 18 – Torque to be applied to screws and connections . 104

– 8 – IEC 61558-2-3:2023 EXV  IEC 2023
Table 19 – Torque test on glands . 106
Table 20 – Clearances in mm . 114
Table 21 – Creepage distances in mm . 115
Table 22 – Distance through insulation in mm . 116
Table 23 – Creepage distances and clearance between terminals for external
connection . 117
Table 104 – Creepage distances and clearances for output terminals . 117
Table 24 – Values of FIW wires with minimum overall diameter and minimum test
voltages according to the total enamel increase . 119
Table A.1 – Width of groove values depending on the pollution degree . 124
Table F.1 – Peak surge current of additional loads. 134
Table I.1 – Dimensions of rectangular copper connectors . 142
Table K.1 – Mandrel diameter . 146
Table K.2 – Oven temperature . 146
Table Q.1 – Degrees of protection against access to hazardous parts indicated by the
first characteristic numeral . 160
Table Q.2 – Degrees of protection against solid foreign objects indicated by the first
characteristic numeral . 160
Table Q.3 – Degrees of protection indicated by the second characteristic numeral . 161
Table R.1 – Impulse test voltage according to 6.1.2.2.1 of IEC 60664-1:2007 . 162

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF TRANSFORMERS, REACTORS,
POWER SUPPLY UNITS AND COMBINATIONS THEREOF –

Part 2-3: Particular requirements and tests for ignition
transformers for gas and oil burners

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
This extended version (EXV) of the official IEC Standard provides the user with the
comprehensive content of the Standard.
made to IEC 61558-1:2017.
The specific content of IEC 61558-2-3:2023 is displayed on a blue background.

– 10 – IEC 61558-2-3:2023 EXV  IEC 2023
International standard IEC 61558-2-3 has been prepared by IEC technical committee 96:
Transformers, reactors, power supply units and combinations thereof. It is an International
Standard.
This third edition cancels and replaces the second edition published in 2010. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) adjustment of structure and references in accordance with IEC 61558-1:2017.
The text of this International Standard is based on the following documents:
Draft Report on voting
96/577/FDIS 96/580/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement,
available at www.iec.ch/members_experts/refdocs. The main document types developed by
IEC are described in greater detail at www.iec.ch/publications.
It has the status of a group safety publication in accordance with IEC Guide 104.
This International Standard is to be used in conjunction with IEC 61558-1:2017.
This document supplements or modifies the corresponding clauses in IEC 61558-1:2017, so
as to convert that publication into the IEC standard: Particular requirements and tests for
ignition transformers for gas and oil burners.
A list of all parts in the IEC 61558 series published under the general title Safety of
transformers, reactors, power supply units and combinations thereof, can be found on the
IEC website.
Future standards in this series will carry the new general title as cited above. Titles of existing
standards in this series will be updated at the time of the next edition.
Where this document states "addition", "modification" or "replacement", the relevant text of
IEC 61558-1:2017 is to be adopted accordingly.
In this document, the following print types are used:
• requirements
...

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Safety of transformers, reactors, power supply units and combinations thereof –
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IEC 61558-2-3 ®
Edition 3.0 2023-06
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
GROUP SAFETY PUBLICATION
Safety of transformers, reactors, power supply units and combinations thereof –
Part 2-3: Particular requirements and tests for ignition transformers for gas and
oil burners
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.180 ISBN 978-2-8322-7157-5

– 2 – IEC 61558-2-3:2023 RLV  IEC 2023
CONTENTS
FOREWORD . 3
INTRODUCTION . 2
1 Scope . 7
2 Normative references . 8
3 Terms and definitions . 8
4 General requirements . 9
5 General notes on tests . 9
6 Ratings . 9
7 Classification . 9
8 Marking and other information . 10
9 Protection against electric shock . 12
10 Change of input voltage setting . 13
11 Output voltage and output current under load . 13
11 Output voltage and output current . 13
12 No-load output voltage . 14
13 Short-circuit voltage . 14
14 Heating . 14
15 Short-circuit and overload protection . 14
16 Mechanical strength . 15
17 Protection against harmful ingress of dust, solid objects and moisture . 15
18 Insulation resistance, dielectric strength and leakage current . 16
19 Construction . 16
20 Components . 17
21 Internal wiring . 17
22 Supply connection and other external flexible cable or cords . 18
23 Terminals for external conductors . 18
24 Provisions for protective earthing. 18
25 Screws and connections . 18
26 Creepage distances, clearances and distances through insulation . 18
27 Resistance to heat, fire and tracking . 19
28 Resistance to rusting . 19
Annexes . 21
Bibliography . 22

Figure 101 – Arcing horn . 20

Table 101 – Symbols indicating the kind of transformer . 12
Table 101 102 – Preferred values of operational parameters . 13
Table 102 103 – Test time for short-circuit test . 15
Table 103 104 – Creepage distances and clearances for output terminals . 19

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF TRANSFORMERS, REACTORS,
POWER SUPPLY UNITS AND COMBINATIONS THEREOF –

Part 2-3: Particular requirements and tests for ignition
transformers for gas and oil burners

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
This redline version of the official IEC Standard allows the user to identify the changes
made to the previous edition IEC 61558-2-3:2010. A vertical bar appears in the margin
wherever a change has been made. Additions are in green text, deletions are in
strikethrough red text.
– 4 – IEC 61558-2-3:2023 RLV  IEC 2023
International standard IEC 61558-2-3 has been prepared by IEC technical committee 96:
Transformers, reactors, power supply units and combinations thereof. It is an International
Standard.
This third edition cancels and replaces the second edition published in 2010. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) adjustment of structure and references in accordance with IEC 61558-1:2017.
The text of this International Standard is based on the following documents:
Draft Report on voting
96/577/FDIS 96/580/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement,
available at www.iec.ch/members_experts/refdocs. The main document types developed by
IEC are described in greater detail at www.iec.ch/publications.
It has the status of a group safety publication in accordance with IEC Guide 104.
This International Standard is to be used in conjunction with IEC 61558-1:2017.
This document supplements or modifies the corresponding clauses in IEC 61558-1:2017, so
as to convert that publication into the IEC standard: Particular requirements and tests for
ignition transformers for gas and oil burners.
A list of all parts in the IEC 61558 series published under the general title Safety of
transformers, reactors, power supply units and combinations thereof, can be found on the
IEC website.
Future standards in this series will carry the new general title as cited above. Titles of existing
standards in this series will be updated at the time of the next edition.
Where this document states "addition", "modification" or "replacement", the relevant text of
IEC 61558-1:2017 is to be adopted accordingly.
In this document, the following print types are used:
• requirements proper: in roman type;
• test specifications: in italic type;
• explanatory matter: in smaller roman type:
In the text of this document, the words in bold are defined in Clause 3.
Subclauses, notes, figures and tables additional to those in IEC 61558-1:2017 are numbered
starting from 101; supplementary annexes are entitled AA, BB, etc.

The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The "colour inside" logo on the cover page of this document indicates that it
contains colours which are considered to be useful for the correct understanding of its
contents. Users should therefore print this document using a colour printer.

The contents of the corrigendum 1 (2023-09) have been included in this copy.

– 6 – IEC 61558-2-3:2023 RLV  IEC 2023
INTRODUCTION
IEC TC 96 has a group safety function in accordance with IEC Guide 104 for transformers
other than those intended to supply distribution networks, in particular transformers and
power supply units intended to allow the application of protective measures against electric
shock as defined by TC 64, which is about Electrical installations and protection against
electric shock, but in certain cases including the limitation of voltage and horizontal safety
function for SELV, in accordance with IEC 60364-4-41.
The group safety function (GSF) is used because of responsibility for safety extra-low voltage
(SELV) in accordance with IEC 61140:2016, 5.2.6 and IEC 60364-4-41:2005, 414.3.1 or
control circuits in accordance with IEC 60204-1:2016, 7.2.4.
The group safety function is used for each part of the IEC 61558-2 series because different
standards of the IEC 61558 series can be combined in one construction but in certain cases
with no limitation of rated output power.
For example, an auto-transformer in accordance with IEC 61558-2-13 can be designed with a
separate SELV-circuit in accordance with the particular requirements for IEC 61558-2-6
relating to the general requirements of IEC 61558-1.

SAFETY OF TRANSFORMERS, REACTORS,
POWER SUPPLY UNITS AND COMBINATIONS THEREOF –

Part 2-3: Particular requirements and tests for ignition
transformers for gas and oil burners

1 Scope
Replacement:
This part of IEC 61558 deals with the safety of ignition transformers for gas and oil burners.
Ignition transformers incorporating electronic circuits are also covered by this document.
NOTE 1 Safety includes electrical, thermal, and mechanical and chemical aspects.
Unless otherwise specified, from here onward, the term transformer covers ignition
transformers for gas and oil burners.
For switch mode power supply units IEC 61558-2-16 is applicable together with this
document. Where two requirements are in conflict, the most severe takes precedence.
This document is applicable to fixed single-phase, air-cooled (natural or forced) associated
dry-type transformers used in the ignition systems of gas and oil burners. The windings may
can be encapsulated or non-encapsulated.
The rated supply voltage does not exceed 1 000 V AC and the rated supply frequency and
the internal operational frequency operating frequencies do not exceed 500 Hz.
The rated short-circuit output current does not exceed 500 mA AC.
The no-load output voltage or the rated output voltage does not exceed 15 000 V AC.
This part is not applicable to external circuits and their components intended to be connected
to the input and output terminals or socket-outlets of the transformers.
NOTE 2 Transformers covered by this document are used in applications where double or reinforced
insulation between circuits is not required by the installation rules or by the end product standard.
NOTE 2 Attention is drawn to the following, if necessary:
• for transformers intended to be used in vehicles, on board ships, and aircraft, additional
requirements (from other applicable standards, national rules, etc.) may be necessary;
• measures to protect the enclosure and the components inside the enclosure against
external influences such as fungus, vermin, termites, solar-radiation, and icing should also
be considered;
• the different conditions for transportation, storage, and operation of the transformers
should also be considered;
• additional requirements in accordance with other appropriate standards and national rules
may can be applicable to transformers intended for use in special environments.
NOTE 3 Future technological development of transformers may can necessitate a need to
increase the upper limit of the frequencies,. Until then this document may can be used as a
guidance document.
– 8 – IEC 61558-2-3:2023 RLV  IEC 2023
This group safety publication focusing on safety guidance is primarily intended to be used as
a product safety standard for the products mentioned in the scope, but is also intended to be
used by technical committees in the preparation of publications for products similar to those
mentioned in the scope of this group safety publication, in accordance with the principles laid
down in IEC Guide 104 and lSO/lEC Guide 51.
One of the responsibilities of a technical committee is, wherever applicable, to make use of
basic safety publications and/or group safety publications in the preparation of its
publications.
2 Normative references
This clause of IEC 61558-1:2017 is applicable, except as follows:
Addition:
IEC 61558-1:20052017, Safety of power transformers, power supplies, reactors and similar
products Safety of transformers, reactors, power supply units and combinations thereof –
Part 1: General requirements and tests
IEC 61558-2-16, Safety of transformers, reactors, power supply units and combinations
thereof – Part 2-16: Particular requirements and tests for switch mode power supply units and
transformers for switch mode power supply units for general applications
ISO 3864-1:20022011, Graphical symbols – Safety colours and safety signs – Part 1: Design
principles for safety signs in workplaces and public areas and safety markings
3 Terms and definitions
This clause of Part 1 is applicable, except as follows:
For the purposes of this document, the terms and definitions given in IEC 61558-1:2017
apply, except as follows:
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1 Transformers
Addition:
3.1.101
ignition transformer
fixed single-phase, air-cooled associated transformer within an ignition system generating
an arc between two electrodes connected to the high voltage output of the transformer
Note 1 to entry: This transformer is intended to be used with a control unit built-in in the ignition system.
3.1.1023.101
rated duty factor
time interval during which the transformer operates, expressed as a percentage of the
duration of the entire cycle
3.5.101
rated short-circuit output current
output current at the rated supply voltage and the rated frequency when the output
winding is short-circuited, assigned to the transformer by the manufacturer
3.5.102
rated no-load output voltage
output voltage when the transformer is connected to the rated supply voltage at the rated
supply frequency under no-load conditions, assigned to the transformer by the
manufacturer
3.5 Ratings
Replacement:
3.5.4 not applicable.
3.5.5 not applicable.
4 General requirements
This clause of IEC 61558-1:2017 is applicable.
5 General notes on tests
This clause of IEC 61558-1:2017 is applicable.
6 Ratings
This clause of IEC 61558-1:2017 is applicable, except as follows:
Addition:
6.101 The rated no-load output voltage shall not exceed 15 000 V AC.
6.102 Void.
6.103 The rated frequency shall not exceed 500 Hz.
6.104 The rated supply voltage shall not exceed 1 000 V AC.
6.105 The rated short-circuit output current shall not exceed 500 mA AC.
6.106 Preferred values of the rated no-load output voltage, the rated short-circuit
output current, and the rated duty factor are given in Table 101 Table 102.
Compliance with the requirements of 6.101 to 6.106 is checked by inspection of the marking.
7 Classification
This clause of IEC 61558-1:2017 is applicable, except as follows:

– 10 – IEC 61558-2-3:2023 RLV  IEC 2023
7.1
Replacement:
7.1 According to their protection against electric shock:
− class I transformers, for specific use only.
NOTE Incorporated transformers are not classified. Their class of protection against electric shock is
determined by the way the transformer is incorporated.
7.2
Replacement:
7.2 According to short-circuit protection or protection against abnormal conditions:
− inherently short-circuit proof transformers;
− fail-safe transformers.
7.4
Replacement:
7.4 According to their mobility:
• fixed ignition transformers for gas and oil burners.
7.5
Replacement:
7.5 According to their duty type:
− continuous duty;
− intermittent duty cycle.
7.6
7.6 This clause of IEC 61558-1:2017 is applicable, except as follows:
Replacement:
7.6.2 This subclause of IEC 61558-1:2017 is not applicable.
7.8
Replacement:
7.8 According to their transient overvoltage condition:
• overvoltage category II.
8 Marking and other information
This clause of IEC 61558-1:2017 is applicable except as follows:

8.1
Replacement:
Items b), c), d), and f) are not applicable.
8.1 h) Replacement:
Transformers shall be marked with one of the graphical symbols shown in 8.11;
h)
Replacement of the content up to the first semi-colon by the following:
relevant graphical symbols shown in Table 101 that indicate the kind of transformer;
8.1 q) Replacement:
p)
Replacement:
Transformers for intermittent duty cycle shall be marked with the rated duty factor
expressed as a percentage and the duration of the entire cycle expressed in minutes.
NOTE Preferred value for the entire cycle of intermittent duty is 3 min.
Addition:
8.1.101 Transformers shall be marked with the graphical symbol according to 8.11 with the
colour in accordance with ISO 3864-1.
For incorporated transformers, the above graphical symbol may can be either on the
transformer or on the equipment placed close to the transformer. If the graphical symbol is
not on the transformer, the manufacturer shall state in the instruction sheets that this
graphical symbol shall be placed on the equipment close to the transformer.
8.1.102 Transformers shall be marked with the rated short-circuit output current in
milliamperes and with the rated no-load output voltage in kV.
8.11
Addition:
– 12 – IEC 61558-2-3:2023 RLV  IEC 2023
Table 101 – Symbols indicating the kind of transformer
Symbol or Explanation or title Identification
graphical symbol
Inherently short-circuit proof ignition
IEC 60417-6198:2013-04
transformer with one end of the output winding
for connection to the protective earth earthing

Inherently short-circuit proof ignition IEC 60417-6199:2013-04
transformer with the midpoint of the output
winding for connection to the protective earth
earthing
Fail-safe ignition transformer with one end of the
IEC 60417-6198:2013-04
output winding for connection to the protective
earth earthing
Fail-safe ignition transformer with the midpoint IEC 60417-6199:2013-04
of the output winding for connection to the
protective earth earthing
8.14
Addition:
Ultimate safety of transformers is dependent upon the control unit and this shall be stated in
the instruction sheet.
9 Protection against electric shock
This clause of IEC 61558-1:2017 is applicable.

10 Change of input voltage setting
This clause of IEC 61558-1:2017 is applicable.
11 Output voltage and output current under load
Replacement:
11 Output voltage and output current
11.1 The output current shall not differ from the rated short-circuit output current by
more than 10 %.
Compliance is checked by the following test:
The output terminals of the transformer are short-circuited by means of a suitable ammeter.
The transformer is connected to the rated supply voltage at the rated frequency and
operated at the rated duty factor until steady-state conditions are reached. The output
current is then measured.
With the supply voltage reduced to 85 %, the minimum output current value shall not be less
than 70 % of the rated short-circuit output current.
11.2 The no-load output voltage shall not differ from the rated no-load output voltage by
more than 10 %.
Compliance is checked by the following test:
The transformer is connected to the rated supply voltage at the rated frequency. The RMS
value of the no-load output voltage is measured. During this test, the protective earthing
terminal shall be connected to the protective earth earthing.
NOTE The test equipment should be selected such that no voltage rise occurs due to the
capacitance (i.e., increase in the capacitance) in the test equipment or measurement network.
Table 101 102 – Preferred values of operational parameters
Type of connection of the
output winding to the M M E E M M M E E M M M
protective earth earthing
Rated duty factor
100 100 100 100 33 33 33 33 33 20 20 20
%
Rated no-load output
voltage
14 10 7 5 14 10 10 7 5 10 10 10
kV
Rated short-circuit output
current
20 20 20 20 30 20 16 20 20 23 20 16
mA
M = midpoint of the output winding for connection to protective earth earthing
E = one end of the output winding for connection to protective earth earthing

– 14 – IEC 61558-2-3:2023 RLV  IEC 2023
12 No-load output voltage
This clause of IEC 61558-1:2017 is not applicable.
13 Short-circuit voltage
This clause of IEC 61558-1:2017 is not applicable.
14 Heating
This clause of IEC 61558-1:2017 is applicable, except as follows:
14.1.1 Temperature-rise test
Addition after the second third paragraph:
For intermittent duty cycle, the test is carried out at the rated duty factor. Temperatures
are measured in the middle of the interval during which the transformer operates.
Replacement of the tenth eleventh paragraph starting with "Transformers are supplied at.",
by the following:
Transformers are connected to 1,06 times the rated supply voltage, at the rated
frequency, and the output winding of the transformer or output terminals are short-
circuited.
15 Short-circuit and overload protection
This clause of IEC 61558-1:2017 is applicable, except as follows:
15.1.1 Short circuit and overload test method
Replacement of the second paragraph:
Compliance is checked by inspection and by the following test, which is performed with the
transformer at ambient temperature, with the same position of the transformer as in the test
of 14.1 14.1.1. The test is carried out at 1,06 times the rated supply voltage, or, for non-
inherently short-circuit proof transformers, at any value of the supply voltage between
0,9 times and 1,1 times the rated supply voltage.
NOTE The overload is only applied to the transformer during the first adjustment of the burner when the
transformer is at ambient temperature.
Addition:
− additionally by the tests of 15.1.101 15.1.1.101.
15.1.1.101 The transformer is connected to an arcing horn as shown in Figure 101 and
supplied at 1,06 times the rated supply voltage at the rated frequency, taking into
consideration the rated duty factor. During the test the arcing horn shall be in a vertical
position and in a draught-free location.

The arcing horn shall be so designed that the rising spark reaches repetitive extinction.
Distance A and angle α shall be adjusted accordingly. The test is carried out for a period of
50 days.
NOTE For transformers having a rated no-load output voltage less than 10 kV, the angle of horn may can be
adjusted for the test in order to reach extinction of the spark.
The length of the high voltage leads shall be less than 300 mm. The leads shall not have
metal sheaths and shall have a copper cross-sectional area of at least 1 mm . The average
distance between these leads should be approximately 40 mm.
During the test, the insulation of the transformer shall not fail.
After this test, the transformer shall withstand the tests according to Clauses 11 and 18,
except the values of Clause 18 shall be reduced by 35 %.
15.2 Inherently short-circuit proof transformers
Replacement:
For inherently short-circuit proof transformers for continuous operation, this test is
covered by the test of 14.1 14.1.1.
For inherently short-circuit proof transformers for intermittent duty cycle, the tests are
performed with the output terminals of the output winding short-circuited. The test time for
transformers for gas burners is twice the time interval during which the transformer
operates (to be calculated from the rated duty factor and the duration of the cycle). The test
time for oil burners is stated in Table 102 Table 103.
Table 102 103 – Test time for short-circuit test
Rated duty factor Test time
% min
Less than 20 8
20 up to 30 15
30 up to and less than 100 30
16 Mechanical strength
This clause of IEC 61558-1:2017 is applicable.
17 Protection against harmful ingress of dust, solid objects and moisture
This clause of IEC 61558-1:2017 is applicable, except as follows:
Addition:
17.101 Transformers for specific use shall have an IP X4 code of a protection index of
IP X4 or higher.
– 16 – IEC 61558-2-3:2023 RLV  IEC 2023
18 Insulation resistance, dielectric strength and leakage current
This clause of IEC 61558-1:2017 is applicable, except as follows:
18.2 Insulation resistance
Table 7: values for double or reinforced insulation are not applicable.
Replacement:
The values of Table 13 for double or reinforced insulation are not applicable.
18.3 Dielectric strength test
Table 8a:
– lines 2 and 4 are not applicable;
– lines 1 and 3 are applicable only for the input circuits of transformers with the core
connected to protective earth.
Replacement:
The values of Table 14 for dielectric strength test voltages apply as follows:
− double or reinforced insulation is not applicable;
− basic insulation is applicable only for the input circuits of transformers with the core
connected to protective earthing.
18.4 Insulation between and within windings
Replacement of the first paragraph with the following:
After the test of 18.3, transformers are tested for 1 min at twice the rated frequency and
with the input voltage increased until the output voltage corresponds to 1,5 times the rated
value. No load is connected.
19 Construction
This clause of IEC 61558-1:2017 is applicable, except as follows:
19.1 General construction
Replacement:
The input and output circuits shall be electrically separated from each other, and the
construction shall be such that there is no possibility of any connection between these
circuits, either directly or indirectly, via other conductive parts, except by deliberate action.
Compliance is checked by inspection and measurements, taking Clauses 18 and 26 into
consideration.
19.1.101 The insulation between input and output winding(s) shall consist of at least
basic insulation.
In addition, the following apply:
The insulation between the input windings and the body, and between the input windings
and the core, shall consist of basic insulation according to the rated supply voltage. The
insulation between the output circuit(s) and the body and between the output circuit(s) and
the core shall be functional insulation. These insulations shall be checked by the tests of
15.1.101 15.1.1.101 and 18.4.
19.1.102 For transformers with intermediate conductive parts not connected to the body
or core, and located between the input and output windings, the insulation between the
intermediate conductive parts and the input windings or between the intermediate
conductive parts and the output windings shall consist of at least basic insulation. The
basic insulation shall be in accordance with the rated supply voltage.
NOTE An intermediate conductive part not separated from the input or output windings or the body by at
least basic insulation, is considered to be connected to the relevant part(s).
19.15 Strain on fixed socket-outlets caused by pin-transformers connection
This subclause of IEC 61558-1:2017 is not applicable.
19.19 Flexible cable or flexible cord connection for class I portable transformers
Modification:
Transformers designed for connection by means of a flexible cable or cord, shall be provided
with a non-detachable flexible cable or cord with a protective earth earthing conductor.
Addition:
19.101 The output circuit(s) shall be connected to protective earth earthing.
However, the output circuit(s) need not to be connected to protective earth earthing if the
output circuit is connected to a measuring device, e.g. an ionisation flame monitor. In this
case either the output circuit needs to be earthed as long as the input circuit is energized, or
the voltage supplied to the measuring device shall be limited to less than 400 V RMS.
NOTE 1 The voltage supplied to the measuring device can e.g. be done by an external voltage limiter and a
series resistor.
NOTE 2 The above requirement serves to avoid voltages higher than 400 V RMS on the subsequent signal wire
between the transformer and the ionisation flame monitor.
19.102 The core, if accessible, shall be connected to protective earth earthing.
Compliance is checked by inspection.
20 Components
This clause of IEC 61558-1:2017 is applicable.
21 Internal wiring
This clause of IEC 61558-1:2017 is applicable.

– 18 – IEC 61558-2-3:2023 RLV  IEC 2023
22 Supply connection and other external flexible cable or cords
This clause of IEC 61558-1:2017 is applicable.
23 Terminals for external conductors
This clause of IEC 61558-1:2017 is applicable.
24 Provisions for protective earthing
This clause of IEC 61558-1:2017 is applicable.
25 Screws and connections
This clause of IEC 61558-1:2017 is applicable.
26 Creepage distances, clearances and distances through insulation
This clause of IEC 61558-1:2017 is applicable, except as follows:
Modification:
This clause applies only to input circuit(s) as the output circuit(s) is (are) connected to
protective earth earthing. In this case, the functional insulation between the core and the
output circuit(s) is considered to be sufficiently checked by the test of 15.1.101 15.1.1.101
and 18.4.
Table 13 is applicable as follows:
Line 1) is applicable, except the working voltage shall be replaced with the rated supply
voltage.
Line 3) is applicable only to the input circuits.
Line 4) is applicable only to the input terminals. For terminals of the output circuits, the
values of Table 103 apply.
Line 5) is applicable with the working voltage replaced with the rated supply voltage.
Replacement:
The values of Table 20, Table 21 and Table 22 apply as follows:
− basic insulation is applicable, except the working voltage shall be replaced with the
rated supply voltage.
− basic insulation between adjacent circuits is applicable only to the input circuits.
The values of Table 23 for terminals for external connection is applicable only to the input
terminals. For terminals of the output circuits, the values of Table 104 apply.

Table 103 104 – Creepage distances and clearances for output terminals
Creepage distance Clearance
Connections to earth Type of insulation
mm mm
Creepage distance and
One end of the output
mm mm
clearance between output
winding (s) for connection
51, ×U 34, ×U
terminals and protective
to protective earth kV kV
earth
Creepage distance and
mm mm
clearance between output 51, ×U 34, ×U
terminals
kV kV
Midpoint of the output
winding (s) for connection
Creepage distance and
to protective earth
mm mm
clearance between output
2,55 ×U 17, ×U
terminals and protective
kV kV
earth
NOTE U is the rated no-load output voltage in kV.

27 Resistance to heat, fire and tracking
This clause of IEC 61558-1:2017 is applicable, except as follows:
27.3 Resistance to abnormal heat under fault conditions
This subclause of IEC 61558-1:2017 is not applicable.
28 Resistance to rusting
This clause of IEC 61558-1:2017 is applicable.

– 20 – IEC 61558-2-3:2023 RLV  IEC 2023
Dimensions in millimetres
Rated output voltage Approximate
gap A
kV
mm
− up to and including 6 2
− More than over 6 up to and
including 10
− More than over 10 up to and
including 15
Figure 101 – Arcing horn
Annexes
The Annexes of IEC 61558-1:2017 are applicable, except as follows:.

Annex C
Creepage distances (cr), clearances (cl)
and distances through insulation (dti) –
Material group II (400 ≤CTI <600)

The Annex C of Part 1 is applicable, except as follows:
Table C.1 is applicable, except as follows:
Line 1) is applicable, except the working voltage shall be replaced by the rated supply
voltage.
Line 3) is applicable only to the input circuits.
Line 4) is applicable only to the input terminals. For terminals of the output circuits, the
values of Table 103 apply.
Line 5) is applicable, except the working voltage shall be replaced with the rated supply
voltage.
Annex D
Creepage distances (cr), clearances (cl)
and distances through insulation (dti) –
Material group I (CTI ≥600)
The Annex D of Part 1 is applicable, except as follows:
Table D.1 is applicable, except as follows:
Line 1) is applicable, except the working voltage shall be replaced with the rated supply
voltage.
Line 3) is applicable only to the input circuits.
Line 4) is applicable only to the input terminals. For terminals of the output circuits, the
values of Table 103 apply.
Line 5) is applicable, except the working voltage shall be replaced with the rated supply
voltage.
– 22 – IEC 61558-2-3:2023 RLV  IEC 2023
Bibliography
The bibliography of IEC 61558-1:2017 is applicable, except as follows:
Addition:
IEC 60204-1:2016, Safety of machinery – Electrical equipment of machines – Part 1: General
requirements
IEC 61558 (all parts), Safety of transformers, reactors, power supply units and combinations
thereof
IEC 61558-2-6, Safety of transformers, reactors, power supply units and combinations thereof
– Part 2-6: Particular requirements and tests for safety isolating transformers and power
supply units incorporating safety isolating transformers for general applications
IEC 61558-2-13, Safety of transformers, reactors, power supply units and combinations
thereof – Part 2-13: Particular requirements and tests for auto-transformers and power supply
units incorporating auto-transformers for general applications
ISO/IEC Guide 51:2014, Safety aspects – Guidelines for their inclusion in standards

____________
IEC 61558-2-3 ®
Edition 3.0 2023-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
GROUP SAFETY PUBLICATION
PUBLICATION GROUPÉE DE SÉCURITÉ
Safety of transformers, reactors, power supply units and combinations thereof –
Part 2-3: Particular requirements and tests for ignition transformers for gas and
oil burners
Sécurité des transformateurs, bobines d'inductance, blocs d'alimentation et des
combinaisons de ces éléments –
Partie 2-3: Exigences particulières et essais pour les transformateurs d'allumage
pour brûleurs à gaz et combustibles liquides

– 2 – IEC 61558-2-3:2023  IEC 2023
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 7
3 Terms and definitions . 7
4 General requirements . 8
5 General notes on tests . 8
6 Ratings . 8
7 Classification . 8
8 Marking and other information .
...

IEC 61558-2-3 ®
Edition 3.0 2023-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
GROUP SAFETY PUBLICATION
PUBLICATION GROUPÉE DE SÉCURITÉ
Safety of transformers, reactors, power supply units and combinations thereof –
Part 2-3: Particular requirements and tests for ignition transformers for gas and
oil burners
Sécurité des transformateurs, bobines d'inductance, blocs d'alimentation et des
combinaisons de ces éléments –
Partie 2-3: Exigences particulières et essais pour les transformateurs d'allumage
pour brûleurs à gaz et combustibles liquides

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IEC 61558-2-3 ®
Edition 3.0 2023-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
GROUP SAFETY PUBLICATION
PUBLICATION GROUPÉE DE SÉCURITÉ

Safety of transformers, reactors, power supply units and combinations thereof –

Part 2-3: Particular requirements and tests for ignition transformers for gas and

oil burners
Sécurité des transformateurs, bobines d'inductance, blocs d'alimentation et des

combinaisons de ces éléments –

Partie 2-3: Exigences particulières et essais pour les transformateurs d'allumage

pour brûleurs à gaz et combustibles liquides

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.180 ISBN 978-2-8322-7064-6

– 2 – IEC 61558-2-3:2023  IEC 2023
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 7
3 Terms and definitions . 7
4 General requirements . 8
5 General notes on tests . 8
6 Ratings . 8
7 Classification . 8
8 Marking and other information . 9
9 Protection against electric shock . 11
10 Change of input voltage setting . 11
11 Output voltage and output current under load . 11
11 Output voltage and output current . 11
12 No-load output voltage . 12
13 Short-circuit voltage . 12
14 Heating . 12
15 Short-circuit and overload protection . 13
16 Mechanical strength . 14
17 Protection against harmful ingress of dust, solid objects and moisture . 14
18 Insulation resistance, dielectric strength and leakage current . 14
19 Construction . 15
20 Components . 16
21 Internal wiring . 16
22 Supply connection and other external flexible cable or cords . 16
23 Terminals for external conductors . 16
24 Provisions for protective earthing. 16
25 Screws and connections . 16
26 Creepage distances, clearances and distances through insulation . 16
27 Resistance to heat, fire and tracking . 17
28 Resistance to rusting . 17
Annexes . 19
Bibliography . 20

Figure 101 – Arcing horn . 18

Table 101 – Symbols indicating the kind of transformer . 11
Table 102 – Preferred values of operational parameters . 12
Table 103 – Test time for short-circuit test . 14
Table 104 – Creepage distances and clearances for output terminals . 17

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF TRANSFORMERS, REACTORS,
POWER SUPPLY UNITS AND COMBINATIONS THEREOF –

Part 2-3: Particular requirements and tests for ignition
transformers for gas and oil burners

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
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with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International standard IEC 61558-2-3 has been prepared by IEC technical committee 96:
Transformers, reactors, power supply units and combinations thereof. It is an International
Standard.
This third edition cancels and replaces the second edition published in 2010. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) adjustment of structure and references in accordance with IEC 61558-1:2017.

– 4 – IEC 61558-2-3:2023  IEC 2023
The text of this International Standard is based on the following documents:
Draft Report on voting
96/577/FDIS 96/580/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement,
available at www.iec.ch/members_experts/refdocs. The main document types developed by
IEC are described in greater detail at www.iec.ch/publications.
It has the status of a group safety publication in accordance with IEC Guide 104.
This International Standard is to be used in conjunction with IEC 61558-1:2017.
This document supplements or modifies the corresponding clauses in IEC 61558-1:2017, so
as to convert that publication into the IEC standard: Particular requirements and tests for
ignition transformers for gas and oil burners.
A list of all parts in the IEC 61558 series published under the general title Safety of
transformers, reactors, power supply units and combinations thereof, can be found on the
IEC website.
Future standards in this series will carry the new general title as cited above. Titles of existing
standards in this series will be updated at the time of the next edition.
Where this document states "addition", "modification" or "replacement", the relevant text of
IEC 61558-1:2017 is to be adopted accordingly.
In this document, the following print types are used:
• requirements proper: in roman type;
• test specifications: in italic type;
• explanatory matter: in smaller roman type:
In the text of this document, the words in bold are defined in Clause 3.
Subclauses, notes, figures and tables additional to those in IEC 61558-1:2017 are numbered
starting from 101; supplementary annexes are entitled AA, BB, etc.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
The contents of the corrigendum 1 (2023-09) have been included in this copy.

INTRODUCTION
IEC TC 96 has a group safety function in accordance with IEC Guide 104 for transformers
other than those intended to supply distribution networks, in particular transformers and
power supply units intended to allow the application of protective measures against electric
shock as defined by TC 64, which is about Electrical installations and protection against
electric shock, but in certain cases including the limitation of voltage and horizontal safety
function for SELV, in accordance with IEC 60364-4-41.
The group safety function (GSF) is used because of responsibility for safety extra-low voltage
(SELV) in accordance with IEC 61140:2016, 5.2.6 and IEC 60364-4-41:2005, 414.3.1 or
control circuits in accordance with IEC 60204-1:2016, 7.2.4.
The group safety function is used for each part of the IEC 61558-2 series because different
standards of the IEC 61558 series can be combined in one construction but in certain cases
with no limitation of rated output power.
For example, an auto-transformer in accordance with IEC 61558-2-13 can be designed with a
separate SELV-circuit in accordance with the particular requirements for IEC 61558-2-6
relating to the general requirements of IEC 61558-1.

– 6 – IEC 61558-2-3:2023  IEC 2023
SAFETY OF TRANSFORMERS, REACTORS,
POWER SUPPLY UNITS AND COMBINATIONS THEREOF –

Part 2-3: Particular requirements and tests for ignition
transformers for gas and oil burners

1 Scope
Replacement:
This part of IEC 61558 deals with the safety of ignition transformers for gas and oil burners.
Ignition transformers incorporating electronic circuits are also covered by this document.
NOTE 1 Safety includes electrical, thermal and mechanical aspects.
Unless otherwise specified, from here onward, the term transformer covers ignition
transformers for gas and oil burners.
For switch mode power supply units IEC 61558-2-16 is applicable together with this
document. Where two requirements are in conflict, the most severe takes precedence.
This document is applicable to fixed single-phase, air-cooled (natural or forced) associated
dry-type transformers used in the ignition systems of gas and oil burners. The windings can
be encapsulated or non-encapsulated.
The rated supply voltage does not exceed 1 000 V AC and the rated supply frequency and
the internal operating frequencies do not exceed 500 Hz.
The rated short-circuit output current does not exceed 500 mA AC.
The no-load output voltage or the rated output voltage does not exceed 15 000 V AC.
This part is not applicable to external circuits and their components intended to be connected
to the input and output terminals or socket-outlets of the transformers.
NOTE 2 Transformers covered by this document are used in applications where double or reinforced
insulation between circuits is not required by the installation rules or by the end product standard.
Attention is drawn to the following, if necessary:
• for transformers intended to be used in vehicles, on board ships, and aircraft, additional
requirements (from other applicable standards, national rules, etc.);
• measures to protect the enclosure and the components inside the enclosure against
external influences such as fungus, vermin, termites, solar-radiation, and icing;
• the different conditions for transportation, storage, and operation of the transformers;
• additional requirements in accordance with other appropriate standards and national rules
can be applicable to transformers intended for use in special environments.
Future technological development of transformers can necessitate a need to increase the
upper limit of the frequencies. Until then this document can be used as a guidance document.
This group safety publication focusing on safety guidance is primarily intended to be used as
a product safety standard for the products mentioned in the scope, but is also intended to be

used by technical committees in the preparation of publications for products similar to those
mentioned in the scope of this group safety publication, in accordance with the principles laid
down in IEC Guide 104 and lSO/lEC Guide 51.
One of the responsibilities of a technical committee is, wherever applicable, to make use of
basic safety publications and/or group safety publications in the preparation of its
publications.
2 Normative references
This clause of IEC 61558-1:2017 is applicable, except as follows:
Addition:
IEC 61558-1:2017, Safety of transformers, reactors, power supply units and combinations
thereof – Part 1: General requirements and tests
IEC 61558-2-16, Safety of transformers, reactors, power supply units and combinations
thereof – Part 2-16: Particular requirements and tests for switch mode power supply units and
transformers for switch mode power supply units for general applications
ISO 3864-1:2011, Graphical symbols – Safety colours and safety signs – Part 1: Design
principles for safety signs and safety markings
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 61558-1:2017
apply, except as follows:
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at https://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1 Transformers
Addition:
3.1.101
ignition transformer
fixed single-phase, air-cooled associated transformer within an ignition system generating
an arc between two electrodes connected to the high voltage output of the transformer
Note 1 to entry: This transformer is intended to be used with a control unit built-in in the ignition system.
3.3.101
rated duty factor
time interval during which the transformer operates, expressed as a percentage of the
duration of the entire cycle
3.5.101
rated short-circuit output current
output current at the rated supply voltage and the rated frequency when the output
winding is short-circuited, assigned to the transformer by the manufacturer

– 8 – IEC 61558-2-3:2023  IEC 2023
3.5.102
rated no-load output voltage
output voltage when the transformer is connected to the rated supply voltage at the rated
supply frequency under no-load conditions, assigned to the transformer by the
manufacturer
3.5 Ratings
Replacement:
3.5.4 not applicable.
3.5.5 not applicable.
4 General requirements
This clause of IEC 61558-1:2017 is applicable.
5 General notes on tests
This clause of IEC 61558-1:2017 is applicable.
6 Ratings
This clause of IEC 61558-1:2017 is applicable, except as follows:
Addition:
6.101 The rated no-load output voltage shall not exceed 15 000 V AC.
6.102 Void.
6.103 The rated frequency shall not exceed 500 Hz.
6.104 The rated supply voltage shall not exceed 1 000 V AC.
6.105 The rated short-circuit output current shall not exceed 500 mA AC.
6.106 Preferred values of the rated no-load output voltage, the rated short-circuit
output current, and the rated duty factor are given in Table 102.
Compliance with the requirements of 6.101 to 6.106 is checked by inspection of the marking.
7 Classification
This clause of IEC 61558-1:2017 is applicable, except as follows:
7.1
Replacement:
7.1 According to their protection against electric shock:

− class I transformers, for specific use only.
NOTE Incorporated transformers are not classified. Their class of protection against electric shock is
determined by the way the transformer is incorporated.
7.2
Replacement:
7.2 According to short-circuit protection or protection against abnormal conditions:
− inherently short-circuit proof transformers;
− fail-safe transformers.
7.4
Replacement:
7.4 According to their mobility:
• fixed ignition transformers for gas and oil burners.
7.5
Replacement:
7.5 According to their duty type:
− continuous duty;
− intermittent duty cycle.
7.6
7.6 This clause of IEC 61558-1:2017 is applicable, except as follows:
Replacement:
7.6.2 This subclause of IEC 61558-1:2017 is not applicable.
7.8
Replacement:
7.8 According to their transient overvoltage condition:
• overvoltage category II.
8 Marking and other information
This clause of IEC 61558-1:2017 is applicable except as follows:
8.1
Replacement:
Items b), c), d), and f) are not applicable.

– 10 – IEC 61558-2-3:2023  IEC 2023
h)
Replacement of the content up to the first semi-colon by the following:
relevant graphical symbols shown in Table 101 that indicate the kind of transformer;
p)
Replacement:
Transformers for intermittent duty cycle shall be marked with the rated duty factor
expressed as a percentage and the duration of the entire cycle expressed in minutes.
NOTE Preferred value for the entire cycle of intermittent duty is 3 min.
Addition:
8.1.101 Transformers shall be marked with the graphical symbol according to 8.11 with the
colour in accordance with ISO 3864-1.
For incorporated transformers, the above graphical symbol can be either on the
transformer or on the equipment placed close to the transformer. If the graphical symbol is
not on the transformer, the manufacturer shall state in the instruction sheets that this
graphical symbol shall be placed on the equipment close to the transformer.
8.1.102 Transformers shall be marked with the rated short-circuit output current in
milliamperes and with the rated no-load output voltage in kV.
8.11
Addition:
Table 101 – Symbols indicating the kind of transformer
Symbol or Explanation or title Identification
graphical symbol
Inherently short-circuit proof ignition
IEC 60417-6198:2013-04
transformer with one end of the output winding
for connection to the protective earthing

Inherently short-circuit proof ignition IEC 60417-6199:2013-04
transformer with the midpoint of the output
winding for connection to the protective earthing

Fail-safe ignition transformer with one end of the IEC 60417-6198:2013-04
output winding for connection to the protective
earthing
Fail-safe ignition transformer with the midpoint IEC 60417-6199:2013-04
of the output winding for connection to the
protective earthing
8.14
Addition:
Ultimate safety of transformers is dependent upon the control unit and this shall be stated in
the instruction sheet.
9 Protection against electric shock
This clause of IEC 61558-1:2017 is applicable.
10 Change of input voltage setting
This clause of IEC 61558-1:2017 is applicable.
11 Output voltage and output current under load
Replacement:
11 Output voltage and output current
11.1 The output current shall not differ from the rated short-circuit output current by
more than 10 %.
Compliance is checked by the following test:

– 12 – IEC 61558-2-3:2023  IEC 2023
The output terminals of the transformer are short-circuited by means of a suitable ammeter.
The transformer is connected to the rated supply voltage at the rated frequency and
operated at the rated duty factor until steady-state conditions are reached. The output
current is then measured.
With the supply voltage reduced to 85 %, the minimum output current value shall not be less
than 70 % of the rated short-circuit output current.
11.2 The no-load output voltage shall not differ from the rated no-load output voltage by
more than 10 %.
Compliance is checked by the following test:
The transformer is connected to the rated supply voltage at the rated frequency. The RMS
value of the no-load output voltage is measured. During this test, the protective earthing
terminal shall be connected to the protective earthing.
The test equipment should be selected such that no voltage rise occurs due to the
capacitance (i.e., increase in the capacitance) in the test equipment or measurement network.
Table 102 – Preferred values of operational parameters
Type of connection of the
output winding to the M M E E M M M E E M M M
protective earthing
Rated duty factor
100 100 100 100 33 33 33 33 33 20 20 20
%
Rated no-load output
voltage
14 10 7 5 14 10 10 7 5 10 10 10
kV
Rated short-circuit output
current
20 20 20 20 30 20 16 20 20 23 20 16
mA
M = midpoint of the output winding for connection to protective earthing
E = one end of the output winding for connection to protective earthing

12 No-load output voltage
This clause of IEC 61558-1:2017 is not applicable.
13 Short-circuit voltage
This clause of IEC 61558-1:2017 is not applicable.
14 Heating
This clause of IEC 61558-1:2017 is applicable, except as follows:
14.1.1 Temperature-rise test
Addition after the third paragraph:

For intermittent duty cycle, the test is carried out at the rated duty factor. Temperatures
are measured in the middle of the interval during which the transformer operates.
Replacement of the eleventh paragraph starting with "Transformers are supplied at.", by the
following:
Transformers are connected to 1,06 times the rated supply voltage, at the rated
frequency, and the output winding of the transformer or output terminals are short-
circuited.
15 Short-circuit and overload protection
This clause of IEC 61558-1:2017 is applicable, except as follows:
15.1.1 Short circuit and overload test method
Replacement of the second paragraph:
Compliance is checked by inspection and by the following test, which is performed with the
transformer at ambient temperature, with the same position of the transformer as in the test
of 14.1.1. The test is carried out at 1,06 times the rated supply voltage, or, for non-
inherently short-circuit proof transformers, at any value of the supply voltage between
0,9 times and 1,1 times the rated supply voltage.
NOTE The overload is only applied to the transformer during the first adjustment of the burner when the
transformer is at ambient temperature.
Addition:
− additionally by the tests of 15.1.1.101.
15.1.1.101 The transformer is connected to an arcing horn as shown in Figure 101 and
supplied at 1,06 times the rated supply voltage at the rated frequency, taking into
consideration the rated duty factor. During the test the arcing horn shall be in a vertical
position and in a draught-free location.
The arcing horn shall be so designed that the rising spark reaches repetitive extinction.
Distance A and angle α shall be adjusted accordingly. The test is carried out for a period of
50 days.
NOTE For transformers having a rated no-load output voltage less than 10 kV, the angle of horn can be
adjusted for the test in order to reach extinction of the spark.
The length of the high voltage leads shall be less than 300 mm. The leads shall not have
metal sheaths and shall have a copper cross-sectional area of at least 1 mm . The average
distance between these leads should be approximately 40 mm.
During the test, the insulation of the transformer shall not fail.
After this test, the transformer shall withstand the tests according to Clauses 11 and 18,
except the values of Clause 18 shall be reduced by 35 %.
15.2 Inherently short-circuit proof transformers
Replacement:
– 14 – IEC 61558-2-3:2023  IEC 2023
For inherently short-circuit proof transformers for continuous operation, this test is
covered by the test of 14.1.1.
For inherently short-circuit proof transformers for intermittent duty cycle, the tests are
performed with the output terminals of the output winding short-circuited. The test time for
transformers for gas burners is twice the time interval during which the transformer
operates (to be calculated from the rated duty factor and the duration of the cycle). The test
time for oil burners is stated in Table 103.
Table 103 – Test time for short-circuit test
Rated duty factor Test time
% min
Less than 20 8
20 up to 30 15
30 up to and less than 100 30
16 Mechanical strength
This clause of IEC 61558-1:2017 is applicable.
17 Protection against harmful ingress of dust, solid objects and moisture
This clause of IEC 61558-1:2017 is applicable, except as follows:
Addition:
17.101 Transformers for specific use shall have a protection index of IP X4 or higher.
18 Insulation resistance, dielectric strength and leakage current
This clause of IEC 61558-1:2017 is applicable, except as follows:
18.2 Insulation resistance
Replacement:
The values of Table 13 for double or reinforced insulation are not applicable.
18.3 Dielectric strength test
Replacement:
The values of Table 14 for dielectric strength test voltages apply as follows:
− double or reinforced insulation is not applicable;
− basic insulation is applicable only for the input circuits of transformers with the core
connected to protective earthing.

18.4 Insulation between and within windings
Replacement of the first paragraph with the following:
After the test of 18.3, transformers are tested for 1 min at twice the rated frequency and
with the input voltage increased until the output voltage corresponds to 1,5 times the rated
value. No load is connected.
19 Construction
This clause of IEC 61558-1:2017 is applicable, except as follows:
19.1 General construction
Replacement:
The input and output circuits shall be electrically separated from each other, and the
construction shall be such that there is no possibility of any connection between these
circuits, either directly or indirectly, via other conductive parts, except by deliberate action.
Compliance is checked by inspection and measurements, taking Clauses 18 and 26 into
consideration.
19.1.101 The insulation between input and output winding(s) shall consist of at least
basic insulation.
In addition, the following apply:
The insulation between the input windings and the body, and between the input windings
and the core, shall consist of basic insulation according to the rated supply voltage. The
insulation between the output circuit(s) and the body and between the output circuit(s) and
the core shall be functional insulation. These insulations shall be checked by the tests of
15.1.1.101 and 18.4.
19.1.102 For transformers with intermediate conductive parts not connected to the body
or core, and located between the input and output windings, the insulation between the
intermediate conductive parts and the input windings or between the intermediate
conductive parts and the output windings shall consist of at least basic insulation. The
basic insulation shall be in accordance with the rated supply voltage.
NOTE An intermediate conductive part not separated from the input or output windings or the body by at
least basic insulation, is considered to be connected to the relevant part(s).
19.15 Strain on fixed socket-outlets caused by pin-transformers connection
This subclause of IEC 61558-1:2017 is not applicable.
19.19 Flexible cable or flexible cord connection for class I portable transformers
Modification:
Transformers designed for connection by means of a flexible cable or cord, shall be provided
with a non-detachable flexible cable or cord with a protective earthing conductor.
Addition:
– 16 – IEC 61558-2-3:2023  IEC 2023
19.101 The output circuit(s) shall be connected to protective earthing.
However, the output circuit(s) need not to be connected to protective earthing if the output
circuit is connected to a measuring device, e.g. an ionisation flame monitor. In this case
either the output circuit needs to be earthed as long as the input circuit is energized, or the
voltage supplied to the measuring device shall be limited to less than 400 V RMS.
NOTE 1 The voltage supplied to the measuring device can e.g. be done by an external voltage limiter and a
series resistor.
NOTE 2 The above requirement serves to avoid voltages higher than 400 V RMS on the subsequent signal wire
between the transformer and the ionisation flame monitor.
19.102 The core, if accessible, shall be connected to protective earthing.
Compliance is checked by inspection.
20 Components
This clause of IEC 61558-1:2017 is applicable.
21 Internal wiring
This clause of IEC 61558-1:2017 is applicable.
22 Supply connection and other external flexible cable or cords
This clause of IEC 61558-1:2017 is applicable.
23 Terminals for external conductors
This clause of IEC 61558-1:2017 is applicable.
24 Provisions for protective earthing
This clause of IEC 61558-1:2017 is applicable.
25 Screws and connections
This clause of IEC 61558-1:2017 is applicable.
26 Creepage distances, clearances and distances through insulation
This clause of IEC 61558-1:2017 is applicable, except as follows:
Modification:
This clause applies only to input circuit(s) as the output circuit(s) is (are) connected to
protective earthing. In this case, the functional insulation between the core and the output
circuit(s) is considered to be sufficiently checked by the test of 15.1.1.101 and 18.4.
Replacement:
The values of Table 20, Table 21 and Table 22 apply as follows:
− basic insulation is applicable, except the working voltage shall be replaced with the
rated supply voltage.
− basic insulation between adjacent circuits is applicable only to the input circuits.
The values of Table 23 for terminals for external connection is applicable only to the input
terminals. For terminals of the output circuits, the values of Table 104 apply.
Table 104 – Creepage distances and clearances for output terminals
Creepage distance Clearance
Connections to earth Type of insulation
mm mm
Creepage distance and
One end of the output
mm mm
clearance between output
winding (s) for connection 51, ×U 34, ×U
terminals and protective
to protective earth kV kV
earth
Creepage distance and
mm mm
clearance between output
51, ×U 34, ×U
terminals
kV kV
Midpoint of the output
winding (s) for connection
Creepage distance and
to protective earth
mm mm
clearance between output
2,55 ×U 17, ×U
terminals and protective
kV kV
earth
NOTE U is the rated no-load output voltage in kV.

27 Resistance to heat, fire and tracking
This clause of IEC 61558-1:2017 is applicable, except as follows:
27.3 Resistance to abnormal heat under fault conditions
This subclause of IEC 61558-1:2017 is not applicable.
28 Resistance to rusting
This clause of IEC 61558-1:2017 is applicable.

– 18 – IEC 61558-2-3:2023  IEC 2023
Dimensions in millimetres
Rated output voltage Approximate
gap A
kV
mm
− up to and including 6 2
− over 6 up to and including 10
− over 10 up to and including 15

Figure 101 – Arcing horn
Annexes
The Annexes of IEC 61558-1:2017 are applicable.

– 20 – IEC 61558-2-3:2023  IEC 2023
Bibliography
The bibliography of IEC 61558-1:2017 is applicable, except as follows:
Addition:
IEC 60204-1:2016, Safety of machinery – Electrical equipment of machines – Part 1: General
requirements
IEC 61558 (all parts), Safety of transformers, reactors, power supply units and combinations
thereof
IEC 61558-2-6, Safety of transformers, reactors, power supply units and combinations thereof
– Part 2-6: Particular requirements and tests for safety isolating transformers and power
supply units incorporating safety isolating transformers for general applications
IEC 61558-2-13, Safety of transformers, reactors, power supply units and combinations
thereof – Part 2-13: Particular requirements and tests for auto-transformers and power supply
units incorporating auto-transformers for general applications
ISO/IEC Guide 51:2014, Safety aspects – Guidelines for their inclusion in standards

____________
– 22 – IEC 61558-2-3:2023  IEC 2023
SOMMAIRE
AVANT-PROPOS . 23
INTRODUCTION . 25
1 Domaine d'application . 26
2 Références normatives . 27
3 Termes et définitions . 27
4 Exigences générales . 28
5 Généralités sur les essais. 28
6 Caractéristiques assignées . 28
7 Classification . 29
8 Marquage et indications . 30
9 Protection contre les chocs électriques . 31
10 Changement de la tension primaire d'alimentation . 31
11 Tension secondaire et courant secondaire en charge . 31
11Tension secondaire et courant secondaire . 31
12 Tension secondaire à vide . 32
13 Tension de court-circuit . 32
14 Échauffements.
...