SIST EN IEC 60310:2026

SLOVENSKI STANDARD
01-oktober-2026
Železniške naprave - Transformatorji vleke in dušilke na tirnih vozilih
Railway applications - Traction transformers and inductors on board rolling stock
Bahnanwendungen - Bahn-Transformatoren und Drosselspulen auf Schienenfahrzeugen
Applications ferroviaires - Transformateurs de traction et bobines d'inductance à bord du
matériel roulant
Ta slovenski standard je istoveten z: EN IEC 60310:2026
ICS:
29.180 Transformatorji. Dušilke Transformers. Reactors
45.060.10 Vlečna vozila Tractive stock
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 60310

NORME EUROPÉENNE
EUROPÄISCHE NORM July 2026
ICS 45.060.01 Supersedes EN 60310:2016; EN 60310:2016/AC:2018-03
English Version
Railway applications - Transformers and inductors on board
rolling stock
(IEC 60310:2026)
Applications ferroviaires - Transformateurs de traction et Bahnanwendungen -Transformatoren und Drosselspulen
bobines d'inductance à bord du matériel roulant auf Bahnfahrzeugen
(IEC 60310:2026) (IEC 60310:2026)
This European Standard was approved by CENELEC on 2026-05-18. CENELEC members are bound to comply with the CEN/CENELEC
Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the
same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 60310:2026 E
European foreword
The text of document 9/3296/FDIS, future edition 5 of IEC 60310, prepared by TC 9 "Electrical
equipment and systems for railways" was submitted to the IEC-CENELEC parallel vote and approved
by CENELEC as EN IEC 60310:2026.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2027-07-31
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2029-07-31
document have to be withdrawn
This document supersedes EN 60310:2016 and all of its amendments and corrigenda (if any).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 60310:2026 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standard indicated:
IEC 60060-1 NOTE Approved as EN IEC 60060-1
IEC 60060-2 NOTE Approved as EN IEC 60060-2
IEC 60076-4 NOTE Approved as EN 60076-4
IEC 60076-11:2018 NOTE Approved as EN IEC 60076-11:2018 (not modified)
IEC 60076-14 NOTE Approved as EN 60076-14
IEC 60077-1 NOTE Approved as EN 60077-1
IEC 60085 NOTE Approved as EN 60085
IEC 60216-1 NOTE Approved as EN IEC 60216-1
IEC 60216-5 NOTE Approved as EN IEC 60216-5
IEC 60270 NOTE Approved as EN IEC 60270
IEC 60505 NOTE Approved as EN 60505
IEC 61287-1 NOTE Approved as EN 61287-1
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments)
applies.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod),
the relevant EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 60076-1 2011 Power transformers - Part 1: General EN 60076-1 2011
IEC 60076-2 - Power transformers - Part 2: Temperature EN 60076-2 -
rise for liquid-immersed transformers
IEC 60076-3 - Power transformers - Part 3: Insulation EN 60076-3 -
levels, dielectric tests and external
clearances in air
IEC 60076-5 - Power transformers - Part 5: Ability to EN 60076-5 -
withstand short circuit
IEC 60076-6 2007 Power transformers - Part 6: Reactors EN 60076-6 2008
IEC 60076-10 - Power transformers - Part 10: EN 60076-10 -
Determination of sound levels
IEC 60076-12 2008 Power transformers - Part 12: Loading - -
guide for dry-type power transformers
IEC 60076-18 - Power transformers - Part 18: EN 60076-18 -
Measurement of frequency response
IEC 60296 - Fluids for electrotechnical applications - EN IEC 60296 -
Mineral insulating oils for electrical
equipment
IEC 60836 - Specifications for unused silicone EN 60836 -
insulating liquids for electrotechnical
purposes
IEC 60850 - Railway applications - Supply voltages of - -
traction systems
IEC 61039 - Classification of insulating liquids EN IEC 61039 -
IEC 61099 - Insulating liquids - Specifications for EN 61099 -
unused synthetic organic esters for
electrical purposes
IEC 61373 — Railway applications - Rolling stock EN 61373 —
equipment - Shock and vibration tests
IEC 61378-1 2011 Converter transformers - Part 1: EN 61378-1 2011
Transformers for industrial applications
IEC 62497-1 2010 Railway applications - Insulation - -
coordination - Part 1: Basic requirements -
Clearances and creepage distances for all
electrical and electronic equipment
+ A1 2013 - -
IEC 62498-1 - Railway applications - Environmental - -
conditions for equipment - Part 1:
Equipment on board rolling stock
ISO 3746 - Acoustics - Determination of sound power EN ISO 3746 -
levels and sound energy levels of noise
sources using sound pressure - Survey
method using an enveloping measurement
surface over a reflecting plane
ISO 9614-1 - Acoustics - Determination of sound power EN ISO 9614-1 -
levels of noise sources using sound
intensity - Part 1: Measurement at discrete
points
ISO 9614-2 - Acoustics - Determination of sound power EN ISO 9614-2 -
levels of noise sources using sound
intensity – Part 2: Measurement by
scanning
Under preparation. Stage at the time of publication: IEC FDIS 61373:2024
IEC 60310 ®
Edition 5.0 2026-04
INTERNATIONAL
STANDARD
Railway applications - Transformers and inductors on board rolling stock

ICS 45.060.01  ISBN 978-2-8327-1073-9

IEC 60310:2026-04(en)
IEC 60310:2026 © IEC 2026
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references . 7
3 Terms, definitions and abbreviated terms . 8
3.1 Terms and definitions. 9
3.1.1 General definitions . 9
3.1.2 Definitions for transformers. 11
3.1.3 Definitions for inductors . 11
3.1.4 Definitions of thermal endurance . 12
3.1.5 Definitions of thermal endurance calculations . 12
3.2 Abbreviated terms . 13
4 Classification . 13
4.1 General . 13
4.2 Classification of transformers . 15
4.3 Classification of inductors . 16
5 Service conditions . 16
6 Rated current and load profile . 16
6.1 Load profile . 16
6.2 Rated current . 16
7 Rated voltage and power of transformer windings . 17
7.1 Rated line-side voltage . 17
7.2 Rated secondary voltage . 17
7.3 Rated power of transformer. 17
8 Transformer tappings . 17
9 Cooling . 17
9.1 Identification of transformers and inductors according to cooling method . 17
9.2 Arrangement of symbols . 18
9.2.1 Enclosed transformers and inductors . 18
9.2.2 Non-enclosed transformers and inductors . 19
9.2.3 Air cooling . 19
10 Temperature limits . 19
10.1 Classification of insulating materials . 19
10.2 Temperature limits of solid insulation . 19
10.3 Temperature limits for liquid . 20
10.4 Temperature limits for other parts . 21
11 Mechanical design . 21
12 Fire protection . 21
13 Rating plates . 21
13.1 General . 21
13.2 Rating plates for transformer. 22
13.3 Rating plates for inductor . 22
14 Tests . 22
14.1 Categories of tests . 22
14.1.1 General . 22
14.1.2 Type tests. 23
IEC 60310:2026 © IEC 2026
14.1.3 Routine tests . 23
14.1.4 Investigation tests. 23
14.2 List of checks and tests . 23
14.3 Tolerances . 25
14.3.1 Tolerances for transformer . 25
14.3.2 Tolerance for inductors . 26
14.4 Test items . 26
14.4.1 Visual checks . 26
14.4.2 Functional tests . 26
14.4.3 Mass . 27
14.4.4 Measurement of winding resistance . 27
14.4.5 Measurement of voltage ratio, polarities and vector groups. 28
14.4.6 Measurement of impedance voltages or short-circuit impedances . 28
14.4.7 Measurement of inductance . 29
14.4.8 Measurement of no-load primary current and losses . 32
14.4.9 Measurement of fundamental load losses . 33
14.4.10 Determination of losses . 33
14.4.11 Temperature-rise test . 34
14.4.12 Insulation resistance test . 39
14.4.13 Dielectric test . 40
14.4.14 Partial discharge test . 46
14.4.15 Short-circuit withstand test . 48
14.4.16 Shock and vibration test . 51
14.4.17 Vibration test with current flowing . 52
14.4.18 Voltage Transmission Ratio (VTR) . 53
14.4.19 Noise measurement . 54
14.4.20 Leakage magnetic flux density measurement . 54
14.4.21 Electrical frequency response analysis (FRA) . 54
14.4.22 Inrush current measurement . 54
Annex A (informative) List of items subject to agreement between purchaser and
manufacturer, and list of information from purchaser or manufacturer . 56
A.1 Items subject to agreement between purchaser and manufacturer . 56
A.1.1 Transformers and inductors . 56
A.1.2 Transformers . 57
A.1.3 Inductors . 58
A.2 Information from purchaser to manufacturer . 59
A.2.1 Transformers and inductors . 59
A.2.2 Transformers . 60
A.2.3 Inductors . 60
A.3 Information from manufacturer to purchaser . 60
A.3.1 Transformers and inductors . 60
A.3.2 Transformers . 61
A.3.3 Inductors . 61
Annex B (informative) Thermal ageing and insulation lifetime . 62
B.1 Insulation lifetime and thermal ageing . 62
B.2 Special considerations for thermal design and test. 63
B.2.1 General . 63
B.2.2 Cooling medium temperature at the external interface . 63
IEC 60310:2026 © IEC 2026
B.2.3 Rated current. 63
B.2.4 Temperature rise test of a dry-type transformer or inductor . 64
B.3 Thermal conformity of the insulation system . 64
B.4 End of life criterion . 64
Annex C (informative) Example of thermal endurance calculation to demonstrate the
suitability of an insulation system for a specified application . 65
C.1 Preliminary . 65
C.2 Example 1 – Temperature limits for a dry-type transformer or inductor . 65
C.3 Example 2 – Thermal endurance calculation . 65
C.3.1 General . 65
C.3.2 Operating conditions to be provided by the purchaser . 66
C.3.3 Thermal endurance characteristics to be provided by the manufacturer . 66
C.3.4 Temperature rise test results . 66
C.3.5 Calculations . 67
Annex D (informative) Wet dielectric tests for dry-type transformers and inductors . 69
D.1 General . 69
D.2 Wet test 1 (optional type test or optional routine test): short soaking . 69
D.3 Wet test 2 (investigation test or optional type test): misting . 70
D.4 Wet test 3 (investigation test): thermal shock – long soaking – misting . 70
D.4.1 General . 70
D.4.2 Temperature conditioning . 70
D.4.3 Thermal shock . 70
D.4.4 Dielectric test . 70
D.5 Common test procedure and criteria for wet dielectric tests . 70
Annex E (informative) Load profiles . 72
Annex F (informative) Background of reference temperature and dielectric test voltage
in IEC 60310 . 73
F.1 General . 73
F.2 Reference temperature . 73
F.3 Dielectric test voltage . 73
Bibliography . 75

Figure 1 – Traction transformer with auxiliary windings fed by AC power supply system . 14
Figure 2 – Traction transformer without auxiliary windings fed by AC power supply
system . 14
Figure 3 – DC locomotive typical circuit diagram . 15
Figure 4 – Energy storage system typical circuit diagram . 15
Figure 5 – Examples of set up for induced voltage withstanding tests . 43
Figure 6 – Examples of set up for separate source voltage withstanding tests . 43
Figure 7 – Examples of impulse test connections for traction, inductor and auxiliary
transformers . 44
Figure 8 – Partial discharge test: voltage versus time . 47
Figure 9 – Configurations for VTR test . 53
Figure 10 – Example of test circuit . 55

Table 1 – Letter symbols for cooling method . 18
Table 2 – Order of symbols . 18
IEC 60310:2026 © IEC 2026
Table 3 – Temperature limits of solid insulation . 20
Table 4 – Temperature limits for liquid . 20
Table 5 – List of checks and tests to be made on transformers or inductors . 24
Table 6 – Tolerances for transformer . 25
Table 7 – Tolerances for inductors . 26
Table 8 – Reference temperatures . 27
Table 9 – Dielectric test voltage . 41
Table 10 – Test method of voltage between terminals withstand test . 45
Table 11 – Partial discharge measurements. 47
Table C.1 – Temperature limits and expected lifetime for a dry-type transformer or
inductor (examples) . 65
Table C.2 – Load cycle histogram . 66
Table C.3 – Temperature histogram . 66
Table C.4 – Temperature rise test results . 67
Table C.5 – Thermal endurance calculation . 67
Table C.6 – Equivalent current and temperatures . 68
Table F.1 – Reference temperatures in IEC 60310:2016 . 73
Table F.2 – Dielectric test voltage in IEC 60310:2016 . 74

IEC 60310:2026 © IEC 2026
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Railway applications -
Transformers and inductors on board rolling stock

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) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which
may be required to implement this document. However, implementers are cautioned that this may not represent
the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
IEC 60310 has been prepared by IEC technical committee 9: Electrical equipment and systems
for railways. It is an International Standard.
This fifth edition cancels and replaces the fourth edition published in 2016. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) typical circuits for transformer and inductors are added;
b) letter symbols for cooling methods are added;
c) dielectric test table is modified;
d) subclauses for the tests of transformers and inductors are restructured;
IEC 60310:2026 © IEC 2026
e) temperature test for dry type transformer and dry type inductors are separated in different
subclauses;
f) requirements for shock and vibration tests are updated according to IEC 61373:20—.
The text of this International Standard is based on the following documents:
Draft Report on voting
9/3296/FDIS 9/3322/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.
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, or
– revised.
IEC 60310:2026 © IEC 2026
1 Scope
This document specifies the terms and definitions, classification, service conditions,
characteristics and test methods for transformers and inductors on board rolling stock.
This document is applicable to traction and auxiliary power transformers installed on board
rolling stock and to the various types of power inductors inserted in the traction and auxiliary
circuits of rolling stock, of dry or liquid-immersed design.
This document is also applicable to the traction transformers of three-phase AC line-side
powered vehicles and to the transformers inserted in the single-phase or polyphase auxiliary
circuits of vehicles, after agreement between purchaser and manufacturer.
This document does not apply to instrument transformers, transformers of a rated output below
1 kVA single-phase or 5 kVA poly-phase, and inductors of a rated output below 1 kVAR single-
phase or 5 kVAR poly-phase on board rolling stock.
This document does not cover accessories such as tap changers, resistors, heat exchangers,
fans, etc., intended for mounting on transformers or inductors, which are tested separately
according to the relevant rules.
NOTE Items requiring agreement between the delivery parties and items of supplementary information and
specification particulars to be provided by the ordering party or manufacturer are given in Annex A.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60076-1:2011, Power transformers - Part 1: General
IEC 60076-2, Power transformers - Part 2: Temperature rise for liquid-immersed transformers
IEC 60076-3, Power transformers - Part 3: Insulation levels, dielectric tests and external
clearances in air
IEC 60076-5, Power transformers - Part 5: Ability to withstand short circuit
IEC 60076-6:2007, Power transformers - Part 6: Reactors
IEC 60076-10, Power transformers - Part 10: Determination of sound levels
IEC 60076-12:2008, Power transformers - Part 12: Loading guide for dry-type transformers
IEC 60076-18, Power transformers - Part 18: Measurement of frequency response
IEC 60296, Fluids for electrotechnical applications - Mineral insulating oils for electrical
equipment
IEC 60836, Specifications for unused silicone insulating liquids for electrotechnical purposes
IEC 60850, Railway applications - Supply voltages of traction systems
IEC 60310:2026 © IEC 2026
IEC 61039, Classification of insulating liquids
IEC 61099, Insulating liquids - Specifications for unused synthetic organic esters for electrical
purposes
IEC 61373:20—, Railway applications - Rolling stock equipment - Shock and vibration tests
IEC 61378-1:2011, Converter transformers - Part 1: Transformers for industrial applications
IEC 62497-1:2010, Railway applications - Insulation coordination - Part 1: Basic requirements -
Clearances and creepage distances for all electrical and electronic equipment
IEC 62497-1:2010/AMD1:2013
IEC 62498-1, Railway applications - Environmental conditions for equipment - Part 1:
Equipment on board rolling stock
ISO 3746, Acoustics - Determination of sound power levels and sound energy levels of noise
sources using sound pressure - Survey method using an enveloping measurement surface over
a reflecting plane
ISO 9614-1, Acoustics - Determination of sound power levels of noise sources using sound
intensity - Part 1: Measurement at discrete points
ISO 9614-2, Acoustics - Determination of sound power levels of noise sources using sound
intensity - Part 2: Measurement by scanning
3 Terms, definitions and abbreviated terms
For the purposes of this document, the terms and definitions given in IEC 60076-1, IEC 62497-1
and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
– IEC Electropedia: available at https://www.electropedia.org/
– ISO Online browsing platform: available at https://www.iso.org/obp
NOTE 1 When the term "transformer" is used alone, it applies to both traction and auxiliary transformers.
NOTE 2 The term "transformer(s)/inductor(s)" appears in clauses applicable to both transformers and inductors to
avoid duplication of text.
NOTE 3 The term "inductor" is used in this document with the same meaning as the term "reactor" mentioned in
IEC 60050-421, IEC 60050-811 and IEC 60076-6.
___________
Under preparation. Stage at the time of publication: IEC FDIS 61373:2024.
IEC 60310:2026 © IEC 2026
3.1 Terms and definitions
3.1.1 General definitions
3.1.1.1
traction transformer
transformer intended to supply the traction circuits, and optionally other equipment
3.1.1.2
auxiliary transformer
transformer intended to supply electrical equipment except
traction circuits
Note 1 to entry: In the energy storage system, the transformer that supplies power to the traction circuit(s) is called
a traction transformer, and that supplying power to the electrical equipment except traction circuit(s) is called an
auxiliary transformer.
3.1.1.3
inductor
two-terminal device characterized essentially by its inductance
[SOURCE: IEC 60050-151:2001, 151-13-25, modified – The notes to entry have been omitted.]
3.1.1.4
load profile
component output power or current versus time under specified conditions
including voltage, rectifier, configuration, harmonic content, etc.
Note 1 to entry: Efficiency for the transformer is agreed between the manufacturer and purchaser.
3.1.1.5
short time emergency loading
unusually heavy loading of a transient nature (less than one time constant of the transformer)
occurring during degraded mode, such as a loss of one traction converter, etc.
[SOURCE: IEC 60076-12:2008, 3.2, modified – ”(less than one time constant of the coil)”
replaced with “(less than one time constant of the transformer)”, “ the occurrence of one or more
unlikely events which seriously disturb normal system loading” replaced with “occurring during
degraded mode”]
3.1.1.6
cooling medium
medium used to extract the heat out of the transformer or inductor e.g. air, water, oil, heat sink,
etc.
IEC 60310:2026 © IEC 2026
3.1.1.7
rated insulation voltage
U
Nm
RMS withstand voltage value assigned by the manufacturer to the equipment or a part of it,
characterising the specified permanent (over 5 min) withstand capability of its insulation
Note 1 to entry: U is a voltage between a live part of equipment and earth or another live part. For rolling stock,
Nm
earth refers to the car body.
Note 2 to entry: For circuits, systems and sub-systems in railway applications, this definition is preferred to "highest
voltage for equipment" which is widely used in international standards.
Note 3 to entry: U is higher than or equal to the working voltage. As a consequence, for circuits directly connected
Nm
to the contact line, U is equal to or higher than U as specified in IEC 60850. For circuits connected to electronic
Nm max1
converter U is higher than or equal to the DC link voltage.
Nm
Note 4 to entry: U is not necessarily equal to the rated voltage which is primarily related to functional
Nm
performance.
[SOURCE: IEC 62497-1:2010, 3.4.4, modified – Addition of the second sentence in Note 3 to
etnry.]
3.1.1.8
nominal voltage
U
n
suitable approximate voltage used to designate or identify a given supply system
3.1.1.9
rated voltage
U
r
value of voltage assigned for a specific operating condition
3.1.1.10
rated impulse voltage
U
Ni
impulse voltage value, characterizing the specified withstand capability of its insulation against
transient over-voltages
3.1.1.11
test voltage
U
a
RMS value derived from U used for separate source voltage, induced voltage, voltage
Nm
between terminals withstand, depending on test carried out
3.1.1.12
recurring peak voltage
U
mT
U
mG
maximum peak value of periodic excursions of the voltage waveform between terminals (U )
mT
)
or between terminals and ground (U
mG
IEC 60310:2026 © IEC 2026
3.1.2 Definitions for transformers
3.1.2.1
voltage transmission ratio
VTR
ratio between the secondary voltage and the primary voltage when a specified impulse or AC
square voltage is applied on the primary
Note 1 to entry: The VTR is expressed as a percentage of this applied voltage.
3.1.2.2
impedance voltage
voltage applied to reach the rated current in short-circuit
Note 1 to entry: This is expressed as a percentage of this applied voltage to the rated voltage at reference
temperature.
Note 2 to entry: When expressed as a percentage or per unit, this is equal to the short circuit impedance referred
in IEC 60076-1:2011, 3.7.1.
3.1.2.3
tolerance
permitted deviation between the declared value of a quantity and the measured value
[SOURCE: IEC 60050-411:2007, 411-36-19]
3.1.3 Definitions for inductors
NOTE Values of inductance for inductors are related to the different classes of utilization and are defined as follows,
with the understanding that they include an indication of the nature and value of the current used in their
measurement.
3.1.3.1
AC inductance
inductance derived from the measurement of the alternating current carried by the inductor
when it is supplied by a sinusoidal alternating voltage of specified value and frequency
[SOURCE: IEC 60050-811:2017, 811-26-36]
3.1.3.2
differential inductance
inductance defined from the derivative of the linked flux as a function of current (equal to the
slope of the magnetic characteristic)
Note 1 to entry: It is derived from the transient record of instantaneous voltage and current in the inductor or from
the measurement of the variation of magnetic flux.
3.1.3.3
incremental inductance
inductance seen by the AC current of a particular value and frequency superimposed on a DC
current through the inductor
Note 1 to entry: The ripple factor of a pulsating current, expressed as a percentage, is conventionally defined by
the formula:
II−
max min
×100
II+
max min
where I and I respectively represent the maximum and minimum values of the current wave.
max min
Note 2 to entry: It is derived from a record of the terminal voltage.
IEC 60310:2026 © IEC 2026
3.1.4 Definitions of thermal endurance
3.1.4.1
thermal endurance
time taken for the deterioration of a selected property (electrical, mechanical, etc.) to reach a
specified end-point at a given temperature
Note 1 to entry: An insulation material mainly ensures the electric performance (dielectric strength) of the conductor
insulation, while the impregnation, casting, sealing, coating, etc., materials mainly ensure the mechanical
performance of the windings (water tightness, resistance to thermal cycling and shock, resistance to vibration or
shocks, thermal conduction, etc.).
Note 2 to entry: An end-point of 50 % of the initial value of the property is used (unless otherwise specified).
3.1.4.2
temperature index
TI
numerical value of the temperature (in degrees Celsius) derived from the thermal endurance
relationship at a time of 20 000 h (unless otherwise specified)
Note 1 to entry: TI is referring to
...