EN IEC 61558-2-23:2025

SLOVENSKI STANDARD
01-maj-2025
Nadomešča:
SIST EN 61558-2-23:2010
Varnost transformatorjev, dušilk, napajalnikov in kombinacij teh elementov - 2-23.
del: Posebne zahteve in preskusi za transformatorje in napajalnike za gradbišča
Safety of transformers, reactors, power supply units and combinations thereof - Part 2-
23: Particular requirements and tests for transformers and power supply units for
construction sites
Sicherheit von Transformatoren, Drosseln, Netzgeräten und entsprechenden
Kombinationen - Teil 2-23: Besondere Anforderungen und Prüfungen für
Transformatoren und Netzgeräte für Baustellen
Sécurité des transformateurs, bobines d'inductance, blocs d'alimentation et des
combinaisons de ces élements - Partie 2-23: Règles particulières et essais pour les
transformateurs et les blocs d'alimentation pour chantiers
Ta slovenski standard je istoveten z: EN IEC 61558-2-23:2025
ICS:
29.180 Transformatorji. Dušilke Transformers. Reactors
91.200 Gradbena tehnologija Construction technology
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 61558-2-23

NORME EUROPÉENNE
EUROPÄISCHE NORM March 2025
ICS 29.180 Supersedes EN 61558-2-23:2010
English Version
Safety of transformers, reactors, power supply units and
combinations thereof - Part 2-23: Particular requirements and
tests for transformers and power supply units for construction
sites
(IEC 61558-2-23:2024)
Sécurité des transformateurs, bobines d'inductance, blocs Sicherheit von Transformatoren, Drosseln, Netzgeräten und
d'alimentation et des combinaisons de ces élements - entsprechenden Kombinationen - Teil 2-23: Besondere
Partie 2-23: Règles particulières et essais pour les Anforderungen und Prüfungen für Transformatoren und
transformateurs et les blocs d'alimentation pour chantiers Netzgeräte für Baustellen
(IEC 61558-2-23:2024) (IEC 61558-2-23:2024)
This European Standard was approved by CENELEC on 2024-10-16. 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
© 2025 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 61558-2-23:2025 E

European foreword
The text of document 96/590/FDIS, future edition 3 of IEC 61558-2-23, prepared by TC 96
"Transformers, reactors, power supply units, and combinations thereof" was submitted to the IEC-
CENELEC parallel vote and approved by CENELEC as EN IEC 61558-2-23:2025.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2026-03-31
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2028-03-31
document have to be withdrawn
This document supersedes EN 61558-2-23:2010 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.
This document is read in conjunction with EN IEC 61558-1:2019.
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 61558-2-23:2024 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 60204-1:2016 NOTE Approved as EN 60204-1:2018
IEC 60364-7-704:2017 NOTE Approved as HD 60364-7-704:2018
IEC 61439-4:2023 NOTE Approved as EN IEC 61439-4:— (not modified)
IEC 61558 series NOTE Approved as EN 61558 series
IEC 61558-2-16:2021 NOTE Approved as EN IEC 61558-2-16:2025 (not modified)

Under preparation. Stage at the time of publication: FprEN IEC 61439-4:2023.
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.
Annex ZA of EN IEC 61558-1:2019 is applicable, except as follows:
Add:
Publication Year Title EN/HD Year
IEC 60068-2-27 2008 Environmental testing - Part 2-27: Tests - EN 60068-2-27 2009
Test Ea and guidance: Shock
IEC 60245-4 2011 Rubber insulated cables - Rated voltages - -
up to and including 450/750 V - Part 4:
Cords and flexible cables
IEC 61558-1 2017 Safety of transformers, reactors, power EN IEC 61558-1 2019
supply units and combinations thereof -
Part 1: General requirements and tests

IEC 61558-2-23 ®
Edition 3.0 2024-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
GROUP ENERGY EFFICIENCY PUBLICATION

PUBLICATION GROUPÉE SUR L'EFFICACITÉ ÉNERGÉTIQUE

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

Part 2-23: Particular requirements and tests for transformers and power supply

units for construction sites
Sécurité des transformateurs, bobines d'inductance, blocs d'alimentation et des

combinaisons de ces élements –

Partie 2-23: Règles particulières et essais pour les transformateurs et les blocs

d'alimentation pour chantiers
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.180  ISBN 978-2-8322-8866-5

– 2 – IEC 61558-2-23:2024 © IEC 2024
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 . 9
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
12 No-load output voltage . 11
13 Short-circuit voltage . 13
14 Heating . 13
15 Short-circuit and overload protection . 13
16 Mechanical strength . 13
17 Protection against harmful ingress of dust, solid objects and moisture . 15
18 Insulation resistance, dielectric strength and leakage current . 15
19 Construction . 15
20 Components . 18
21 Internal wiring . 18
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 . 18
28 Resistance to rusting . 18
Annexes . 20
Annex L (normative) Routine tests (production tests) . 21
Bibliography . 22

Figure 101 – Impact test for horizontal surface . 19
Figure 102 – Impact test for vertical surface . 19

Table 101 – Symbols indicating the kind of transformer . 10
Table 102 – Output voltage ratio for safety isolating transformers . 12
Table 103 – Output voltage ratio for isolating transformers . 12

IEC 61558-2-23:2024 © IEC 2024 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF TRANSFORMERS, REACTORS,
POWER SUPPLY UNITS AND COMBINATIONS THEREOF –

Part 2-23: Particular requirements and tests for transformers and
power supply units for construction sites

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 61558-2-23 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;
b) new symbol for power supply units with linearly regulated output voltage.

– 4 – IEC 61558-2-23:2024 © IEC 2024
The text of this International Standard is based on the following documents:
Draft Report on voting
96/590/FDIS 96/596/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/standardsdev/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
transformers and power supply units for construction sites.
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 adapted 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, or
• revised.
IEC 61558-2-23:2024 © IEC 2024 – 5 –
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 IEC 61558-2 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 61558-2-23:2024 © IEC 2024
SAFETY OF TRANSFORMERS, REACTORS,
POWER SUPPLY UNITS AND COMBINATIONS THEREOF –

Part 2-23: Particular requirements and tests for transformers and
power supply units for construction sites

1 Scope
Replacement:
This part of IEC 61558 deals with the safety of transformers for construction sites and power
supply units incorporating transformers for construction sites. 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 transformers for
construction sites and power supply units incorporating transformers for construction sites.
This document is applicable to stationary or portable, single-phase or polyphase, air-cooled
(natural or forced) independent or associated transformers, being isolating or safety
isolating dry-type transformers for the use on construction sites. The windings can be
encapsulated or non-encapsulated.
For power supply units (linear) this document is applicable. 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.
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 output does not exceed:
– 25 kVA for single-phase transformers;
– 40 kVA for polyphase transformers.
This document is applicable to transformers without limitation of the rated output subject to
an agreement between the purchaser and the manufacturer.
NOTE 2 Transformers intended to supply distribution networks are not included in the scope.
Isolating transformers for construction sites have a no-load output voltage and a rated
output voltage exceeding 50 V AC and not exceeding 250 V AC.
Safety isolating transformers for construction sites have a no-load output voltage and a
rated output voltage not exceeding 50 V AC.
NOTE 3 This document is applicable to transformers for the supply of electricity in locations as specified in
IEC 60364-7-704. The latter also specifies the protection by using an earthed midpoint or starpoint of the output
winding.
NOTE 4 Transformers covered by this document are used in applications where it is required by the installation
rules or by the appliance specification for protection purposes.

IEC 61558-2-23:2024 © IEC 2024 – 7 –
When the transformers are incorporated into low voltage switchgear and controlgear
assemblies for construction sites as specified in IEC 61439-4, the additional requirements
of IEC 61439-4 apply to the assembly.
NOTE 5 For transformers filled with liquid dielectric or pulverised material, such as sand, additional requirements
are under consideration.
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.
It is possible that the future technological development of transformers will require an increase
in the upper limit of the frequencies. Until then this document may 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
IEC 61558-1:2017, Clause 2 is applicable, except as follows:
Addition:
IEC 60068-2-27:2008, Environmental testing – Part 2-27: Tests – Test Ea and guidance: Shock
IEC 60245-4:2011, Rubber insulated cables – Rated voltages up to and including 450/750 V –
Part 4: Cords and flexible cables
...