IEC 61558-1:2017

IEC 61558-1 ®
Edition 3.0 2017-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
GROUP SAFETY PUBLICATION
PUBLICATION GROUPÉE DE SÉCURITÉ
Safety of transformers, reactors, power supply units and combinations thereof –
Part 1: General requirements and tests

Sécurité des transformateurs, bobines d’inductance, blocs d’alimentation et
des combinaisons de ces éléments –
Partie 1: Exigences générales et essais

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IEC 61558-1 ®
Edition 3.0 2017-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
GROUP SAFETY PUBLICATION
PUBLICATION GROUPÉE DE SÉCURITÉ

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

Part 1: General requirements and tests

Sécurité des transformateurs, bobines d’inductance, blocs d’alimentation et

des combinaisons de ces éléments –

Partie 1: Exigences générales et essais

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.180 ISBN 978-2-8322-4750-1

– 2 – IEC 61558-1:2017 © IEC 2017
CONTENTS
FOREWORD . 9
INTRODUCTION . 11
1 Scope . 14
2 Normative references . 16
3 Terms and definitions . 19
3.1 Transformers . 20
3.2 General terms . 23
3.3 Operations and protections . 24
3.4 Circuits and windings . 26
3.5 Ratings . 27
3.6 No-load values . 29
3.7 Insulation . 29
3.8 Touch current and protective earthing conductor current . 33
4 General requirements . 33
5 General notes on tests . 34
6 Ratings . 36
7 Classification . 36
8 Marking and other information . 37
9 Protection against electric shock . 43
9.1 General . 43
9.2 Protection against contact with hazardous-live-parts . 44
9.2.1 Determination of hazardous-live-parts . 44
9.2.2 Accessibility to hazardous-live-parts . 44
9.2.3 Accessibility to non hazardous-live-part . 47
9.3 Protection against hazardous electrical discharge . 47
10 Change of input voltage setting . 47
11 Output voltage and output current under load . 48
12 No-load output voltage . 49
13 Short-circuit voltage . 49
14 Heating . 49
14.1 General requirements . 49
14.1.1 Temperature-rise test . 49
14.1.2 Alternative temperature-rise test . 51
14.1.3 Determination of steady-state conditions . 54
14.2 Application of 14.1 or 14.3 according to the insulation system. 55
14.3 Accelerated ageing test for undeclared class of insulation system . 56
14.3.1 General . 56
14.3.2 Heat run . 56
14.3.3 Vibration . 57
14.3.4 Moisture treatment . 57
14.3.5 Measurements . 57
15 Short circuit and overload protection. 57
15.1 General requirements . 57
15.1.1 Short circuit and overload test method . 57

15.1.2 Alternative short circuit and overload test method . 60
15.2 Inherently short-circuit proof transformers . 60
15.3 Non-inherently short-circuit proof transformers. 60
15.4 Non-short-circuit proof transformers . 61
15.5 Fail-safe transformers . 61
16 Mechanical strength . 62
16.1 General . 62
16.2 Stationary transformers . 62
16.3 Portable transformers (except portable transformers with integral pins for
introduction in socket-outlet in the fixed wiring) . 63
16.4 Portable transformers provided with integral pins for introduction in socket-
outlets of the fixed wiring . 63
16.4.1 General requirements . 63
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 . 64
16.5 Additional requirements for transformers to be used in vehicles and railway
applications . 65
16.5.1 Transformers to be used in vehicles and railway applications . 65
16.5.2 Test requirements for the transportation of transformers . 66
17 Protection against harmful ingress of dust, solid objects and moisture . 67
17.1 Degrees of protection provided by enclosures (IP code) . 67
17.1.1 General requirements . 67
17.1.2 Tests on transformers with enclosure . 68
17.2 Humidity treatment . 70
18 Insulation resistance, dielectric strength and leakage current . 71
18.1 General . 71
18.2 Insulation resistance . 71
18.3 Dielectric strength test . 72
18.4 Insulation between and within windings . 74
18.5 Touch current and protective earthing conductor current . 74
18.5.1 General . 74
18.5.2 Touch current . 75
18.5.3 Protective earthing conductor current . 76
19 Construction . 77
19.1 General construction . 77
19.1.1 General . 77
19.1.2 Auto-transformers . 77
19.1.3 Separating transformers . 78
19.1.4 Isolating transformers and safety isolating transformers . 79
19.2 Flammability of materials . 81
19.3 Short-circuit characteristics of portable transformers . 81
19.4 Class II transformer contact prevention of accessible conductive parts . 81
19.5 Class II transformer insulation reassembling after service . 81
19.6 Loosening of wires, screws or similar parts . 82
19.7 Resistor or capacitor connection with accessible conductive parts . 82
19.8 Bridging of separated conductive parts by resistors or capacitors . 82
19.9 Insulating material separating input and output windings . 83
19.10 Accidental contact protection against hazardous-live-parts provided by
isolating coating . 83

– 4 – IEC 61558-1:2017 © IEC 2017
19.11 Insulating material of handles, operating levers, knobs and similar parts. 84
19.12 Winding construction . 84
19.13 Fixing of handles, operating levers and similar parts . 88
19.14 Fixing of covers providing protection against electric shock . 88
19.15 Strain on fixed socket-outlets caused by pin-transformers connection . 89
19.16 Portable transformers for use in irregular or harsh conditions . 89
19.17 Drain hole of transformers protected against ingress of water . 89
19.18 Plug connected transformers protected against ingress of water . 89
19.19 Flexible cable or flexible cord connection for class I portable transformers . 89
19.20 SELV- and PELV-circuit separation of live parts . 89
19.21 Protection against contact for FELV-circuit. 90
19.22 Protective earthing regarding class II transformers . 90
19.23 Protective earthing regarding class III transformers . 91
20 Components . 91
21 Internal wiring . 96
22 Supply connection and other external flexible cables or cords . 96
23 Terminals for external conductors . 103
24 Provisions for protective earthing. 104
25 Screws and connections . 106
26 Creepage distances, clearances and distances through insulation . 108
26.1 General . 108
26.2 Creepage distances and clearances . 109
26.2.1 General . 109
26.2.2 Windings covered with adhesive tape . 109
26.2.3 Uncemented insulationing parts . 109
26.2.4 Cemented insulating parts . 109
26.2.5 Enclosed parts (e.g. by impregnation or potting) . 110
26.3 Distance through insulation . 111
27 Resistance to heat, fire and tracking . 122
27.1 General . 122
27.2 Resistance to heat . 122
27.2.1 General . 122
27.2.2 External accessible parts . 122
27.2.3 Internal parts . 123
27.3 Resistance to abnormal heat under fault conditions . 123
27.4 Resistance to fire . 124
27.4.1 General . 124
27.4.2 External accessible parts . 125
27.4.3 Internal parts . 125
27.5 Resistance to tracking . 126
28 Resistance to rusting . 126
Annex A (normative) Measurement of creepage distances and clearances. 127
Annex B (normative) Testing a series of transformers . 131
B.1 General . 131
B.2 Requirements . 131
B.3 Constructional inspection . 132
Annex C (void) . 133

Annex D (void) . 134
Annex E (normative) Glow-wire test . 135
E.1 General . 135
E.2 Severity . 135
E.3 Conditioning . 135
E.4 Test procedure . 135
Annex F (normative) Requirements for manually operated switches which are parts of
transformers assembly . 136
F.1 General . 136
F.2 Switches tested as a separate component . 136
F.3 Switches tested as part of the transformer . 136
Annex G (normative) Tracking test . 139
G.1 General . 139
G.2 Test specimen . 139
G.3 Test apparatus . 139
G.4 Procedure . 139
Annex H (normative) Electronic circuits . 140
H.1 General . 140
H.2 General notes on tests (addition to Clause 5). 140
H.3 Short circuit and overload protection (addition to Clause 15) . 140
H.4 Creepage distances, clearances and distances through insulation (addition
to Clause 26) . 142
Annex I (informative) Dimensions for rectangular cross-section connectors of
transformers, basic dimensions and coordination . 144
Annex J (normative) Measuring network for touch-currents . 146
Annex K (normative) Insulated winding wires . 147
K.1 General . 147
K.2 Type tests . 147
K.2.1 General . 147
K.2.2 Dielectric strength test . 147
K.2.3 Flexibility and adherence . 147
K.2.4 Heat shock . 148
K.2.5 Retention of dielectric strength after bending . 148
K.3 Testing during manufacturing . 149
K.3.1 General . 149
K.3.2 Routine test . 149
K.3.3 Sampling test . 149
Annex L (normative) Routine tests (production tests) . 150
L.1 General . 150
L.2 Protective earthing continuity test . 150
L.3 Checking of no-load output voltage . 150
L.4 Dielectric strength test . 150
L.5 Checking of protective devices mounting . 151
L.6 Visual inspection . 151
L.7 Repetition test after routine dielectric strength test . 151
Annex M (informative) Examples to be used as a guide for 19.1 . 152
M.1 General . 152
M.2 Coil-former . 152

– 6 – IEC 61558-1:2017 © IEC 2017
M.2.1 Concentric type . 152
M.2.2 Side-by-side type . 153
M.3 Windings . 153
M.3.1 Without screen . 153
M.3.2 With screen . 154
Annex N (informative) Examples for checking points of dielectric strength test voltages . 155
Annex O (void) . 157
Annex P (informative) Examples for measurement points of creepage distances and
clearances . 158
Annex Q (informative) Explanation of IP numbers for degrees of protection . 161
Q.1 General . 161
Q.2 Degrees of protection against access to hazardous parts and against solid
foreign objects . 161
Q.3 Degrees of protection against ingress of water . 163
Annex R (normative) Explanations of the application of 6.1.2.2.1 of IEC 60664-1:2007 . 164
R.1 Impulse dielectric test . 164
R.2 Example. 164
Annex S (void) . 166
Annex T (void) . 167
Annex U (void) . 168
Annex V (informative) Symbols to be used for thermal cut-outs . 169
V.1 General . 169
V.2 Non-self-resetting thermal cut-out (see 3.3.4) . 169
V.3 Self-resetting thermal cut-out (see 3.3.3) . 169
Annex W (normative) Coated printed circuit boards . 170
W.1 Preamble . 170
W.2 General . 170
W.3 Cold . 170
W.4 Rapid change of temperature . 170
W.5 Additional tests . 170
Bibliography . 171
Index of defined terms . 173

Figure 1 – IEC 61558 principle . 12
Figure 2 – Mounting box for flush-type transformer . 35
Figure 3 – Test pin (see IEC 61032, test probe 13) . 45
Figure 4 – Standard test finger (see IEC 61032, test probe B) . 46
Figure 5 – Example of back-to-back method – Single phase . 53
Figure 6 – Example of back-to-back method – Three phase . 53
Figure 7 – Amplitude spectrum density for random testing . 66
Figure 8 – Normalised spectrum of shock . 67
Figure 9 – Test voltage sequence . 74
Figure 10 – Test configuration: single-phase equipment on star TN or TT system . 76
Figure 11 – Abrasion resistance test for insulating coated layers . 84
Figure 12 – Flexing test apparatus . 100

Figure 13 – Test arrangement for checking mechanical withstanding of insulating
materials in thin sheet layers . 114
Figure 14 – Ball-pressure apparatus . 122
Figure A.1 – Example 1. 127
Figure A.2 – Example 2. 128
Figure A.3 – Example 3. 128
Figure A.4 – Example 4. 128
Figure A.5 – Example 5. 129
Figure A.6 – Example 6. 129
Figure A.7 – Example 7. 130
Figure A.8 – Example 8. 130
Figure H.1 – Example of an electronic circuit with low-power points . 143
Figure J.1 – Measuring network for touch-current . 146
Figure M.1 – Examples for concentric type constructions . 152
Figure M.2 – Examples for side-by-side type constructions . 153
Figure M.3 – Examples for winding constructions without screen . 153
Figure M.4 – Examples for wrapped winding constructions . 154
Figure M.5 – Examples for winding constructions with screen . 154
Figure N.1 – Transformer of class I construction with metal enclosure . 155
Figure N.2 – Transformer of class II construction with metal enclosure . 156
Figure N.3 – Transformer of class II construction with enclosure of insulating material . 156
Figure P.1 – Transformer of class I construction . 158
Figure P.2 – Transformer of class I construction with earthed metal screen . 159
Figure P.3 – Transformer of class II construction with metal enclosure . 159
Figure P.4 – Transformer of class II construction with enclosure of insulating material . 160
Figure V.1 – Restored by manual operation . 169
Figure V.2 – Restored by disconnection of the supply . 169
Figure V.3 – Thermal link (see 3.3.5) . 169
Figure V.4 – Self-resetting thermal cut-out . 169

Table 1 – Symbols used on equipment or in instructions . 41
Table 2 – Values of maximum temperatures in normal use . 54
Table 3 – Explanation of the maximum winding temperatures required in Table 2 . 55
Table 4 – Test temperature and testing time (in days) per cycle . 56
Table 5 – Maximum values of temperatures under short-circuit or overload conditions . 59
Table 6 – Values of T and k for fuses . 60
Table 7 – Pull force on pins . 64
Table 8 – Conditions for vibration testing (random) . 65
Table 9 – Amplitude spectrum density ASD values for accelerated life testing . 65
Table 10 – Frequency values depending on the weight of the specimen . 66
Table 11 – Excitation values for vibration testing . 66
Table 12 – Solid-object-proof transformer test . 69
Table 13 – Values of insulation resistance . 72

– 8 – IEC 61558-1:2017 © IEC 2017
Table 14 – Table of dielectric strength test voltages. 73
Table 15 – Limits for currents . 76
Table 16 – Nominal cross-sectional areas of external flexible cables or cords . 98
Table 17 – Pull and torque to be applied to external flexible cables or cords fixed to
stationary and portable transformers . 102
Table 18 – Torque to be applied to screws and connections . 107
Table 19 – Torque test on glands . 108
Table 20 – Clearances in mm . 115
Table 21 – Creepage distances in mm . 116
Table 22 – Distance through insulation in mm . 117
Table 23 – Creepage distances and clearance between terminals for external
connection . 118
Table 24 – Values of FIW wires with minimum overall diameter and minimum test
voltages according to the total enamel increase . 120
Table A.1 – Width of groove values depending on the pollution degree . 127
Table F.1 – Peak surge current of additional loads. 137
Table I.1 – Dimensions of rectangular copper connectors . 144
Table K.1 – Mandrel diameter . 148
Table K.2 – Oven temperature . 148
Table Q.1 – Degrees of protection against access to hazardous parts indicated by the
first characteristic numeral . 162
Table Q.2 – Degrees of protection against solid foreign objects indicated by the first
characteristic numeral . 162
Table Q.3 – Degrees of protection indicated by the second characteristic numeral . 163
Table R.1 – Impulse test voltage according to 6.1.2.2.1 of IEC 60664-1:2007 . 164

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

Part 1: General requirements and tests

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