Safety of transformers, reactors, power supply units and similar products for supply voltages up to 1 100 V - Part 2-6: Particular requirements and tests for safety isolating transformers and power supply units incorporating safety isolating transformers

IEC 61558-2-6:2009 deals with the safety of safety isolating transformers for general applications and power supply units incorporating safety isolating transformers for general applications. Transformers incorporating electronic circuits are also covered by this standard. This second edition cancels and replaces the first edition published in 1997. It constitutes a technical revision. The main changes consist of updating this part in accordance with Part 1 (2005), and increasing the supply voltages up to 1 100 V to be in line with the standards of TC 14. This part has the status of a group safety publication in accordance with IEC Guide 104. This part is intended to be used in conjunction with the latest edition of IEC 61558-1 and its amendments. It is based on the second edition (2005) of that standard. It is the recommendation of the committee that the content of this publication be adopted for implementation nationally not earlier than 12 months from the date of publication.

Sécurité des transformateurs, bobines d'inductance, blocs d'alimentation et produits analogues pour des tensions d'alimentation jusqu'à 1 100 V - Partie 2-6: Règles particulières et essais pour les transformateurs de sécurité et les blocs d'alimentation incorporant des transformateurs de sécurité

La CEI 61558-2-6:2009 traite de la sécurité des transformateurs de sécurité pour applications d'ordre général et des blocs d'alimentation incorporant des transformateurs de sécurité pour applications d'ordre général. Les transformateurs incorporant des circuits électroniques sont également couverts par la présente norme. Cette deuxième édition annule et remplace la première édition publiée en 1997. Elle constitue une révision technique. Les principales modifications consistent en la mise à jour de la présente partie 2-6 conformément à la Partie 1 (2005), et l'augmentation de la tension d'alimentation jusqu'à 1 100 V pour être en conformité avec les normes du TC 14. La présente partie a le statut de publication groupée de sécurité conformément au Guide CEI 104. La présente partie est destinée à être utilisée avec la dernière édition de la CEI 61558-1 et ses amendements. Elle est basée sur la seconde édition (2005) de cette norme. Le comité recommande que le contenu de cette publication soit entériné au niveau national au plus tôt 12 mois après la date de publication.

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IEC 61558-2-6
Edition 2.0 2009-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
GROUP SAFETY PUBLICATION
PUBLICATION GROUPÉE DE SÉCURITÉ
Safety of transformers, reactors, power supply units and similar products for
supply voltages up to 1 100 V –

Part 2-6: Particular requirements and tests for safety isolating transformers and

power supply units incorporating safety isolating transformers
Sécurité des transformateurs, bobines d’inductance, blocs d'alimentation et
produits analogues pour des tensions d’alimentation jusqu'à 1 100 V –

Partie 2-6: Règles particulières et essais pour les transformateurs de sécurité et

les blocs d'alimentation incorporant des transformateurs de sécurité
IEC 61558-2-6:2009
---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED
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---------------------- Page: 2 ----------------------
IEC 61558-2-6
Edition 2.0 2009-02
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
GROUP SAFETY PUBLICATION
PUBLICATION GROUPÉE DE SÉCURITÉ
Safety of transformers, reactors, power supply units and similar products for
supply voltages up to 1 100 V –

Part 2-6: Particular requirements and tests for safety isolating transformers and

power supply units incorporating safety isolating transformers
Sécurité des transformateurs, bobines d’inductance, blocs d'alimentation et
produits analogues pour des tensions d’alimentation jusqu'à 1 100 V –

Partie 2-6: Règles particulières et essais pour les transformateurs de sécurité et

les blocs d'alimentation incorporant des transformateurs de sécurité
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX
ICS 29.180 ISBN 978-2-88910-541-0
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – 61558-2-6 © IEC:2009
CONTENTS

FOREWORD...........................................................................................................................3

1 Scope...............................................................................................................................5

2 Normative references .......................................................................................................6

3 Terms and definitions .......................................................................................................6

4 General requirements .......................................................................................................6

5 General notes on tests .....................................................................................................6

6 Ratings.............................................................................................................................6

7 Classification....................................................................................................................7

8 Marking and other information ..........................................................................................7

9 Protection against electric shock ......................................................................................7

10 Change of input voltage setting ........................................................................................7

11 Output voltage and output current under load ...................................................................7

12 No-load output voltage .....................................................................................................7

13 Short-circuit voltage .........................................................................................................8

14 Heating ............................................................................................................................8

15 Short-circuit and overload protection ................................................................................8

16 Mechanical strength .........................................................................................................9

17 Protection against harmful ingress of dust, solid objects and moisture..............................9

18 Insulation resistance, dielectric strength and leakage current ...........................................9

19 Construction .....................................................................................................................9

20 Components ...................................................................................................................11

21 Internal wiring.................................................................................................................11

22 Supply connection and other external flexible cable or cords ..........................................11

23 Terminals for external conductors...................................................................................11

24 Provisions for protective earthing ...................................................................................11

25 Screws and connections .................................................................................................11

26 Creepage distances, clearances and distances through insulation..................................12

27 Resistance to heat, fire and tracking...............................................................................12

28 Resistance to rusting......................................................................................................12

Annexes ...............................................................................................................................13

Annex C Creepage distances (cr), clearances (cl) and distances through insulation

(dti) Material group II (400 ≤CTI <600) ..................................................................................13

Annex D Creepage distances (cr), clearances (cl) and distances through insulation

(dti) Material group I (CTI ≥600) ............................................................................................13

Annex R Explanations of the application of 4.2 of IEC 60664-1:2007 (see IEC 61558-1

Subclause 26.2)....................................................................................................................13

Bibliography..........................................................................................................................14

Table 101 – Output voltage difference ....................................................................................

---------------------- Page: 4 ----------------------
61558-2-6 © IEC:2009 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
SAFETY OF TRANSFORMERS, REACTORS, POWER SUPPLY UNITS
AND SIMILAR PRODUCTS FOR SUPPLY VOLTAGES UP TO 1 100 V –
Part 2-6: Particular requirements and tests
for safety isolating transformers and power supply units
incorporating safety isolating transformers
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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any

equipment declared to be in conformity with an IEC Publication.

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.

International standard IEC 61558-2-6 has been prepared by IEC technical committee 96:

Transformers, reactors, power supply units and similar products for low voltages up to

1 100 V.

This second edition cancels and replaces the first edition published in 1997. It constitutes a

technical revision. The main changes consist of updating this part in accordance with Part 1

(2005), and increasing the supply voltages up to 1 100 V to be in line with the standards of TC

14.

This part has the status of a group safety publication in accordance with IEC Guide 104:

(1997): The preparation of safety publications and the use of basic safety publications and

group safety publications.
---------------------- Page: 5 ----------------------
– 4 – 61558-2-6 © IEC:2009
The text of this standard is based on the following documents:
FDIS Report on voting
96/317/FDIS 96/322/RVD

Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

This part is intended to be used in conjunction with the latest edition of IEC 61558-1 and its

amendments. It is based on the second edition (2005) of that standard.

This part supplements or modifies the corresponding clauses in IEC 61558-1, so as to convert

that publication into the IEC standard: Particular requirements and tests for safety isolating

transformers and power supply units incorporating safety isolating transformers.

A list of all parts of the IEC 61558 series can be found on the IEC website under the title:

Safety of transformers, reactors, power supply units and similar products for supply voltages

up to 1 100 V.

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 a particular subclause of Part 1 is not mentioned in this part, that subclause applies as

far as is reasonable. Where this part states "addition", "modification" or "replacement", the

relevant text of Part 1 is to be adapted accordingly.
In this part, 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 part, the words in bold are defined in Clause 3.

Subclauses, notes, figures and tables additional to those in Part 1 are numbered starting from

101; supplementary annexes are entitled AA, BB, etc.

The committee has decided that the contents of this publication will remain unchanged until

the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in

the data related to the specific publication. At this date, the publication will be

• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

NOTE The attention of National Committees is drawn to the fact that equipment manufacturers and testing

organizations may need a transitional period following publication of a new, amended or revised IEC publication in

which to make products in accordance with the new requirements and to equip themselves for conducting new or

revised tests.

It is the recommendation of the committee that the content of this publication be adopted for implementation

nationally not earlier than 12 months from the date of publication.
---------------------- Page: 6 ----------------------
61558-2-6 © IEC:2009 – 5 –
SAFETY OF TRANSFORMERS, REACTORS, POWER SUPPLY UNITS
AND SIMILAR PRODUCTS FOR SUPPLY VOLTAGES UP TO 1 100 V –
Part 2-6: Particular requirements and tests
for safety isolating transformers and power supply units
incorporating safety isolating transformers
1 Scope
Replacement:

This part of IEC 61558 deals with the safety of safety isolating transformers for general

applications and power supply units incorporating safety isolating transformers for

general applications. Transformers incorporating electronic circuits are also covered by this

standard.
NOTE 1 Safety includes electrical, thermal and mechanical aspects.

Unless otherwise specified, from here onward, the term transformer covers safety isolating

transformers for general applications and power supply units incorporating safety

isolating transformers for general applications.

NOTE 2 For power supply units (linear) this part is applicable. For switch mode power supply units, IEC 61558-2-16 is

applicable together with this part.

This part is applicable to stationary or portable, single-phase or polyphase, air-cooled

(natural or forced) independent or associated dry- type transformers. The windings may be

encapsulated or non-encapsulated.

The rated supply voltage does not exceed 1 100 V a.c., and the rated supply frequency

and the internal operating frequencies do not exceed 500 Hz.
The rated output does not exceed:
– 10 kVA for single-phase transformers;
– 16 kVA for polyphase transformers.

This part is applicable to transformers without limitation of the rated output subject to an

agreement between the purchaser and the manufacturer.

NOTE 3 Transformers intended to supply distribution networks are not included in the scope.

The no-load output voltage or the rated output voltage does not exceed 50 V a.c. or 120 V

ripple-free d.c.

This part is not applicable to external circuits and their components intended to be connected

to the input terminals and output terminals of the transformers.

Transformers covered by this part are used in applications where double or reinforced

insulation between circuits is required by the installation rules or by the end product

standard.
NOTE 4 Attention is drawn to the following:

– 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;
---------------------- Page: 7 ----------------------
– 6 – 61558-2-6 © IEC:2009

– 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 be applicable to

transformers intended for use in special environments.

NOTE 5 Future technological development of transformers may necessitate a need to increase the upper limit of

the frequencies, until then this part may be used as a guidance document.
2 Normative references
This clause of Part 1 is applicable except as follows.
Addition:

IEC 61558-1 :2005, Safety of power transformers, power supplies, reactors and similar

products – Part 1: General requirements and tests
3 Terms and definitions
This clause of Part 1 is applicable.
4 General requirements
This clause of Part 1 is applicable.
5 General notes on tests
This clause of Part 1 is applicable.
6 Ratings
This clause of Part 1 is applicable except as follows.
Addition:

6.101 The rated output voltage shall not exceed 50 V a.c. or 120 V ripple-free d.c.

6.102 The rated output shall not exceed:
– 10 kVA for single-phase transformers;
– 16 kVA for polyphase transformers.

Transformers without limitation of the rated output shall be subject to agreement between

the purchaser and the manufacturer.

6.103 The rated supply frequency and the internal operating frequencies shall not

exceed 500 Hz.
6.104 The rated supply voltage shall not exceed 1 100 V a.c.

Compliance with the requirements of 6.101 to 6.104 is checked by inspection of the marking.

---------------------- Page: 8 ----------------------
61558-2-6 © IEC:2009 – 7 –
7 Classification
This clause of Part 1 is applicable.
8 Marking and other information
This clause of Part 1 is applicable except as follows:
8.1 h) Replacement:

Replace the first sentence by the following: Relevant graphical symbols shown in 8.11

indicating the kind of transformer;
8.11 Addition:
Symbol or Explanation or title Identification
graphical symbol
Fail-safe safety isolating transformer 60417-5222
Non-short-circuit-proof safety isolating 60417-5946
transformer
Short-circuit-proof safety isolating transformer 60417-5947
(inherently or non-inherently)
9 Protection against electric shock
This clause of Part 1 is applicable.
10 Change of input voltage setting
This clause of Part 1 is applicable.
11 Output voltage and output current under load
This clause of Part 1 is applicable.
12 No-load output voltage
This clause of Part 1 is applicable except as follows:
Addition:

The no-load output voltage is measured when the transformer is connected to the rated

supply voltage at the rated supply frequency at ambient temperature.

12.101 The no-load output voltage shall not exceed 50 V a.c. or 120 V ripple-free d.c.

---------------------- Page: 9 ----------------------
– 8 – 61558-2-6 © IEC:2009

For independent transformers, this output voltage limitation applies even when output

windings, not intended for interconnection, are connected in series.

NOTE The requirement for series connection does not apply to associated or IP 00 transformers.

12.102 The difference between the no-load output voltage and the output voltage under

load shall not be excessive.

The difference is expressed as a percentage of the latter voltage calculated according to the

following formula:
U −U
no-load load
×100 (%)
load
where U is the no-load output voltage and U is the output voltage under load.
no-load load

Compliance with the requirements of 12.101 and 12.102 is checked by measuring the no-load

output voltage at the ambient temperature when the transformer, is connected to the

rated supply voltage at the rated supply frequency.
The difference shall not exceed the values shown in Table 101.
Table 101 – Output voltage difference
Type of transformer Difference between no-load output voltage and
Rated output output voltage under load
VA %
Inherently short-circuit-proof transformers:
– up to and including 63 100
– over 63 up to and including 630 50
– over 630 20
Other transformers:
– up to and including 10 100
– over 10 up to and including 25 50
– over 25 up to and including 63 20
– over 63 up to and including 250 15
– over 250 up to and including 630 10
– over 630 5
13 Short-circuit voltage
This clause of Part 1 is applicable.
14 Heating
This clause of Part 1 is applicable.
15 Short-circuit and overload protection
This clause of Part 1 is applicable.
---------------------- Page: 10 ----------------------
61558-2-6 © IEC:2009 – 9 –
16 Mechanical strength
This clause of Part 1 is applicable.
17 Protection against harmful ingress of dust, solid objects and moisture
This clause of Part 1 is applicable.
18 Insulation resistance, dielectric strength and leakage current
This clause of Part 1 is applicable.
19 Construction
This clause of Part 1 is applicable except as follows:
Replace 19.1 of Part 1 by the following:

19.1 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.

19.1.1 The insulation between input and output winding(s) shall consist of double or

reinforced insulation (rated for the working voltage) unless the requirements in 19.1.3 are

complied with.
In addition, the following applies:

– for class I transformers not intended for connection to the mains supply by means of

a plug, the insulation between the input windings and the body connected to earth

shall consist of at least basic insulation rated for the input voltage. The insulation

between the output windings and the body connected to earth, shall consist of at
least basic insulation (rated for the output voltage);

– for class I transformers intended for connection to the mains supply by means of a

plug, the insulation between the input windings and the body shall consist of at least

basic insulation, and the insulation between the output windings and the body shall

consist of at least supplementary insulation (both basic and supplementary
insulations rated for the working voltage);

– for class II transformers, the insulation between the input windings and the body

shall consist of double or reinforced insulation (rated for the input voltage). The

insulation between the output windings and the body, shall consist of double or
reinforced insulation (rated for the output voltage), for SELV circuits basic
insulation only is required.

19.1.2 For transformers with intermediate conductive parts (e.g. the iron core) not

connected to the body and located between the input and output windings, the following

requirements are applicable:

19.1.2.1 for class I and class II transformers, the insulation between the input and

output windings via the intermediate conductive parts shall consist of double or
reinforced insulation (rated for the working voltage);
---------------------- Page: 11 ----------------------
– 10 – 61558-2-6 © IEC:2009
– for class II transformers, the insulation between the input windings and the
body, and between the output windings and the body via the intermediate
conductive parts shall consist of double or reinforced insulation (rated for the
input and output voltage), for SELV circuits basic insulation only is required;
– for transformer different from independent (IP00), the insulation between the
input and output windings via the intermediate conductive parts shall consist
of double or reinforced insulation (rated for the working voltage).
19.1.2.2 as alternative to 19.1.2.1 for class I transformer not intended to be

connected by means of a plug and for transformer different from independent (IP00),

if the construction assure that all laminated plates of the iron core are connected to

earth (e.g by soldering / welding) and if in the data sheet or instruction sheet clearly

state that the safety of the transformer depends on the earth connection and that is

not possible to use in class II equipment, than the following apply: the insulation

between the input windings and the intermediate conductive part connected to
earth, and between the output windings and the intermediate conductive part

connected to earth, shall consist of at least basic insulation (rated for the input and

output voltage);

19.1.2.3 in addition to 19.1.2.1 and 19.1.2.2 the insulation between the intermediate

conductive parts and the input windings, and between the intermediate conductive

parts and the output windings shall consist of at least basic insulation (rated for the

input and output voltage). 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).

19.1.3 For class I transformers not intended for connection to the mains supply by means

...

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