SIST EN IEC 61558-2-4:2025

Safety of transformers, reactors, power supply units and combinations thereof - Part 2-4: Particular requirements and tests for isolating transformers and power supply units incorporating isolating transformers for general applications

Replacement
This part of IEC 61558 deals with the safety of isolating transformers for general applications and power supply units incorporating isolating transformers for general applications.
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 isolating transformers for general applications and power supply units incorporating isolating transformers for general applications.
For power supply units (linear) this document is applicable. For switch mode power supply units, IEC 61558-2-16 is applicable.
This document is applicable to stationary or portable, single-phase or polyphase, air-cooled (natural or forced) independent or associated dry- type transformers. 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 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.
The no-load output voltage or the rated output voltage does exceed 50 V AC or 120 V ripplefree DC, and where applicable, does not exceed 500 V AC or 708 V ripple-free DC.
The no-load output voltage and the rated output voltage may be up to 1 000 V AC or 1 415 V ripple-free DC for special applications.
This document is not applicable to external circuits and their components intended to be connected to the input terminals and output terminals of the transformers.
NOTE 3 Transformers covered by this document are used in applications where double or reinforced insulation between circuits is required by the installation rules or by the end product standard.
Attention is drawn to the following:
- additional requirements for transformers intended to be used in vehicles, on board ships, and aircraft (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 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 TCs 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 TC is, wherever applicable, to make use of BSPs and/or GSPs in the preparation of its publications.

Sicherheit von Transformatoren, Drosseln, Netzgeräten und entsprechenden Kombinationen - Teil 2-4: Besondere Anforderungen und Prüfungen für Trenntransformatoren und Netzgeräte, die Trenntransformatoren enthalten, für allgemeine Anwendungen

Sécurité des transformateurs, bobines d'inductance, blocs d'alimentation et combinaisons de ces éléments - Partie 2-4 : Exigences particulières et essais pour les transformateurs de séparation des circuits et les blocs d'alimentation incorporant des transformateurs de séparation des circuits pour applications d'ordre général

IEC 61558-2-4:2021 est disponible sous forme de IEC 61558-2-4:2021 RLV qui contient la Norme internationale et sa version Redline, illustrant les modifications du contenu technique depuis l'édition précédente.

Varnost transformatorjev, dušilk, napajalnikov in kombinacij teh - 2-4. del: Posebne zahteve in preskusi za ločilne transformatorje in napajalnike z ločilnimi transformatorji za splošno uporabo

General Information

• Status: Published
• Publication Date: 03-Apr-2025
• ICS: 29.180 - Transformers. Reactors
• Technical Committee: I96 - Imaginarni 96
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 06-Jul-2021
• Due Date: 10-Sep-2021
• Completion Date: 04-Apr-2025
• Directive: 2014/35/EU - Directive 2014/35/EU of the European Parliament and of the Council of 26 February 2014 on the harmonisation of the laws of the Member States relating to the making available on the market of electrical equipment designed for use within certain voltage limits
• Ref Project: EN IEC 61558-2-4:2025 - Safety of transformers, reactors, power supply units and combinations thereof - Part 2-4: Particular requirements and tests for isolating transformers and power supply units incorporating isolating transformers for general applications

Relations

• Replaces: SIST EN 61558-2-4:2010 - Safety of transformers, reactors, power supply units and similar products for voltages up to 1100 V -- Part 2-4: Particular requirements and tests for isolating transformers and power supply units incorporating isolating transformers
• Effective Date: 16-Jul-2019

Standards Content (Sample)

SLOVENSKI STANDARD
01-maj-2025
Nadomešča:
SIST EN 61558-2-4:2010
Varnost transformatorjev, dušilk, napajalnikov in kombinacij teh - 2-4. del:
Posebne zahteve in preskusi za ločilne transformatorje in napajalnike z ločilnimi
transformatorji za splošno uporabo
Safety of transformers, reactors, power supply units and combinations thereof - Part 2-4:
Particular requirements and tests for isolating transformers and power supply units
incorporating isolating transformers for general applications
Sicherheit von Transformatoren, Drosseln, Netzgeräten und entsprechenden
Kombinationen - Teil 2-4: Besondere Anforderungen und Prüfungen für
Trenntransformatoren und Netzgeräte, die Trenntransformatoren enthalten, für
allgemeine Anwendungen
Sécurité des transformateurs, bobines d'inductance, blocs d'alimentation et
combinaisons de ces éléments - Partie 2-4 : Exigences particulières et essais pour les
transformateurs de séparation des circuits et les blocs d'alimentation incorporant des
transformateurs de séparation des circuits pour applications d'ordre général
Ta slovenski standard je istoveten z: EN IEC 61558-2-4:2025
ICS:
29.180 Transformatorji. Dušilke Transformers. Reactors
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 61558-2-4

NORME EUROPÉENNE
EUROPÄISCHE NORM March 2025
ICS 29.180 Supersedes EN 61558-2-4:2009
English Version
Safety of transformers, reactors, power supply units and
combinations thereof - Part 2-4: Particular requirements and
tests for isolating transformers and power supply units
incorporating isolating transformers for general applications
(IEC 61558-2-4:2021)
Sécurité des transformateurs, bobines d'inductance, blocs Sicherheit von Transformatoren, Drosseln, Netzgeräten und
d'alimentation et combinaisons de ces éléments - Partie 2-4 entsprechenden Kombinationen - Teil 2-4: Besondere
: Exigences particulières et essais pour les transformateurs Anforderungen und Prüfungen für Trenntransformatoren
de séparation des circuits et les blocs d'alimentation und Netzgeräte, die Trenntransformatoren enthalten, für
incorporant des transformateurs de séparation des circuits allgemeine Anwendungen
pour applications d'ordre général (IEC 61558-2-4:2021)
(IEC 61558-2-4:2021)
This European Standard was approved by CENELEC on 2021-06-22. 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 61558-2-4:2025 E

European foreword
The text of document 96/505/FDIS, future edition 3 of IEC 61558-2-4, 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 61558-2-4:2025.
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 61558-2-4:2009 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 61558-2-4:2021 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 61558 series NOTE Approved as EN 61558 series
IEC 60204-1:2016 NOTE Approved as EN 60204-1:2018
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 is applicable, except as follows:
Add:
Publication Year Title EN/HD Year
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 61558-2-4 ®
Edition 3.0 2021-05
INTERNATIONAL
STANDARD
GROUP SAFETY PUBLICATION
Safety of transformers, reactors, power supply units and combinations thereof –

Part 2-4: Particular requirements and tests for isolating transformers and power

supply units incorporating isolating transformers for general applications

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.180 ISBN 978-2-8322-9790-2

– 2 – IEC 61558-2-4:2021 © IEC 2021
CONTENTS
FOREWORD . 3
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 8
3 Terms and definitions . 8
4 General requirements . 8
5 General notes on tests . 8
6 Ratings . 9
7 Classification . 9
8 Marking and other information . 9
9 Protection against electric shock . 10
10 Change of input voltage setting . 10
11 Output voltage and output current under load . 10
12 No-load output voltage . 10
13 Short-circuit voltage . 11
14 Heating . 11
15 Short-circuit and overload protection . 11
16 Mechanical strength . 12
17 Protection against harmful ingress of dust, solid objects and moisture . 12
18 Insulation resistance, dielectric strength and leakage current . 12
19 Construction . 12
20 Components . 12
21 Internal wiring . 12
22 Supply connection and other external flexible cable or cords . 12
23 Terminals for external conductors . 12
24 Provisions for protective earthing. 12
25 Screws and connections . 12
26 Creepage distances, clearances and distances through insulation . 12
27 Resistance to heat, fire and tracking . 12
28 Resistance to rusting . 13
Annexes . 14
Bibliography . 15

Table 101 – Symbols indicating the kind of transformer . 10
Table 102 – Output voltage ratio . 11

IEC 61558-2-4:2021 © IEC 2021 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF TRANSFORMERS, REACTORS,
POWER SUPPLY UNITS AND COMBINATIONS THEREOF –

Part 2-4: Particular requirements and tests
for isolating transformers and power supply units
incorporating isolating transformers for general applications

FOREWORD
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