IEC 61558-2-13:2009

Safety of transformers, reactors, power supply units and similar products for supply voltages up to 1 100 V - Part 2-13: Particular requirements and tests for auto transformers and power supply units incorporating auto transformers

IEC 61558-2-13:2009 deals with the safety of auto transformers for general applications and power supply units incorporating auto 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 1999. 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 2-13: Règles particulières et essais pour les autotransformateurs et les blocs d'alimentation incorporant des autotransformateurs

La CEI 61558-2-13:2009 traite de la sécurité des autotransformateurs pour applications d'ordre général et des blocs d'alimentation incorporant des autotransformateurs 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 1999. Elle constitue une révision technique. Les principales modifications consistent en la mise à jour de la présente partie 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.

General Information

• Status: Published
• Publication Date: 10-Feb-2009
• ICS: 29.180 - Transformers. Reactors
• Technical Committee: TC 96 - Transformers and reactors
• Drafting Committee: MT 1 - TC 96/MT 1
• Current Stage: DELPUB - Deleted Publication
• Start Date: 19-Oct-2022
• Completion Date: 02-Aug-2021

Relations

• Revises: IEC 61558-2-13:1999 - Safety of power transformers, power supply units and similar devices - Part 2-13: Particular requirements for auto-transformers for general use
• Effective Date: 05-Sep-2023
• Revised: IEC 61558-2-13:2022 - Safety of transformers, reactors, power supply units and combinations thereof - Part 2-13: Particular requirements and tests for auto-transformers and power supply units incorporating auto-transformers for general applications
• Effective Date: 05-Sep-2023

Overview

IEC 61558-2-13:2009 is an international standard published by the International Electrotechnical Commission (IEC). It focuses on the safety requirements and tests for auto transformers and power supply units incorporating auto transformers. Targeting supply voltages up to 1,100 V AC, this standard applies to general-purpose transformers used in various electrical and electronic applications. It addresses transformers both with and without electronic circuits and includes both single-phase and polyphase air-cooled dry-type units.

This second edition, published in 2009, replaces the first edition from 1999. Key revisions include harmonization with IEC 61558-1 (2005) and increasing the voltage rating limit to align with Technical Committee 14 standards. IEC 61558-2-13 is intended to be used alongside IEC 61558-1 and focuses on electrical, thermal, and mechanical safety aspects of auto transformers.

Key Topics

• Scope and Applicability: The standard covers stationary or portable auto transformers and power supply units incorporating these transformers, with rated power limits of up to 2 kVA for single-phase and 10 kVA for polyphase units. Rated output power can reach 40 kVA for single-phase transformers.

• Safety Requirements: Emphasizes protection against electric shock, mechanical strength, insulation resistance, dielectric strength, heating, short-circuit and overload protection, and prevention of ingress of dust and moisture.

• Testing Procedures: Specifies tests for output voltage, no-load voltage, short-circuit voltage, insulation properties, mechanical robustness, and thermal resistance, among others. Tests ensure compliance with safety criteria and reliable operation under normal and fault conditions.

• Construction and Components: Addresses proper design and selection of components, including internal wiring and terminals, ensuring adherence to required creepage distances, clearances, and protection against fire and rusting.

• Marking and Documentation: Requires clear marking for ratings, supply voltage settings, safety instructions, and manufacturer information to facilitate safe installation and maintenance.

Applications

• General Purpose Auto Transformers: Used in industrial and commercial settings where voltage adjustment or isolation at supply voltages up to 1,100 V is required.

• Power Supply Units with Auto Transformers: Applicable in devices and systems where power conversion relies on auto transformers, including linear power supplies that incorporate electronic circuits.

• Dry-Type Transformers: Suitable for air-cooled transformers used in environments requiring strict electrical, thermal, and mechanical safety.

• Single-Phase and Polyphase Systems: The standard applies for both single-phase units (common in residential and small commercial power systems) and polyphase units (used extensively in industrial power distribution).

Related Standards

• IEC 61558-1: General safety requirements for transformers, reactors, power supply units, and similar products. IEC 61558-2-13 supplements and modifies Part 1 to cater specifically to auto transformers.

• IEC 61558-2-16: Addresses safety requirements for switch mode power supply units with incorporated auto transformers. Used in conjunction with IEC 61558-2-13 when applicable.

• IEC Guide 104: Provides guidelines for the preparation of safety publications. IEC 61558-2-13 is recognized as a group safety publication under this guide.

• Other IEC 61558 Series: The broader IEC 61558 series covers safety of transformers, reactors, and power supply units for supply voltages up to 1,100 V, with specific parts focusing on different transformer types or usage scenarios.

Practical Value

IEC 61558-2-13:2009 ensures manufacturers, testing bodies, and users of auto transformers and power supply units achieve a high level of safety and reliability. The standard supports:

• Enhanced Electrical Safety: Protecting users and equipment from shock hazards and electrical faults.

• Thermal and Mechanical Protection: Minimizing risks of overheating, fire, and mechanical failure.

• Consistent Quality and Compliance: Assisting manufacturers in meeting international benchmarks for product design and testing.

• Market Access and Regulatory Acceptance: Facilitating national adoption of unified safety requirements, improving trust and acceptance in global markets.

• Clear Testing Protocols: Offering detailed guidance on safety and performance testing, crucial for certification processes.

By following IEC 61558-2-13, stakeholders can ensure that auto transformers and power supplies incorporating them are both safe and effective for their intended electrical applications, thereby reducing potential hazards and enhancing operational efficiency.

Standards Content (Sample)

IEC 61558-2-13 ®
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 2-13: Particular requirements and tests for auto transformers and power
supply units incorporating auto transformers

Sécurité des transformateurs, bobines d’inductance, blocs d'alimentation et
produits analogues pour des tensions d’alimentation jusqu'à 1 100 V –
Partie 2-13: Règles particulières et essais pour les autotransformateurs et les
blocs d'alimentation incorporant des autotransformateurs

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IEC 61558-2-13 ®
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 2-13: Particular requirements and tests for auto transformers and power
supply units incorporating auto transformers

Sécurité des transformateurs, bobines d’inductance, blocs d'alimentation et
produits analogues pour des tensions d’alimentation jusqu'à 1 100 V –
Partie 2-13: Règles particulières et essais pour les autotransformateurs et les
blocs d'alimentation incorporant des autotransformateurs

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
N
CODE PRIX
ICS 29.180 ISBN 978-2-88910-542-7
– 2 – 61558-2-13 © IEC:2009
CONTENTS
FOREWORD.4
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 .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 .11
17 Protection against harmful ingress of dust, solid objects and moisture.11
18 Insulation resistance, dielectric strength and leakage current .11
19 Construction .12
20 Components .12
21 Internal wiring.13
22 Supply connection and other external flexible cable or cords .13
23 Terminals for external conductors.13
24 Provisions for protective earthing .13
25 Screws and connections .13
26 Creepage distances, clearances and distances through insulation.13
27 Resistance to heat, fire and tracking.13
28 Resistance to rusting.13
Annexes .14
Annex C Creepage distances (cr), clearances (cl) and distances through insulation
(dti) Material group II (400 ≤CTI <600) .14
Annex D Creepage distances (cr), clearances (cl) and distances through insulation
(dti) Material group I (CTI ≥600) .14
Annex R Explanations of the application of 4.2 of IEC 60664-1:2007 (see IEC 61558-1
Subclause 26.2).14
Bibliography.15

Figure 101 – Windings .
Figure 102 – Tappings .8
Figure 103 – Windings separated by functional isolation .8

61558-2-13 © IEC:2009 – 3 –
Table 101 – Output voltage difference .11

– 4 – 61558-2-13 © IEC:2009
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF TRANSFORMERS, REACTORS, POWER SUPPLY UNITS
AND SIMILAR PRODUCTS FOR SUPPLY VOLTAGES UP TO 1 100 V –

Part 2-13: Particular requirements and tests
for auto transformers and power supply units
incorporating auto 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
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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 61558-2-13 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 1999. 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.
61558-2-13 © IEC:2009 – 5 –
The text of this standard is based on the following documents:
FDIS Report on voting
96/318/FDIS 96/323/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 auto transformers
and power supply units incorporating auto 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.

– 6 – 61558-2-13 © IEC:2009
SAFETY OF TRANSFORMERS, REACTORS, POWER SUPPLY UNITS
AND SIMILAR PRODUCTS FOR SUPPLY VOLTAGES UP TO 1 100 V –

Part 2-13: Particular requirements and tests
for auto transformers and power supply units
incorporating auto transformers

1 Scope
Replacement:
This part of IEC 61558 deals with the safety of auto transformers for general applications
and power supply units incorporating auto 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 auto
transformers for general applications and power supply units incorporating auto
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 core power does not exceed:
– 2 kVA for single-phase transformers;
– 10 kVA for polyphase transformers.
The rated output does not exceed:
– 40 kVA for single-phase transformers;
– 200 kVA for polyphase transformers.
This part is applicable to transformers without limitation of the core power and the rated
output both being subject to an agreement between the purchaser and the manufacturer.
Where applicable, the no-load output voltage or the rated output voltage does not exceed
1 000 V a.c. or 1 415 V ripple-free d.c., and for independent transformers, the no-load
output voltage and the rated output voltage exceeds 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 only in applications where no insulation
between circuits is required by the installation rules or by the end product standard.
NOTE 3 Attention is drawn to the following:

61558-2-13 © IEC:2009 – 7 –
– 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;
– 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 4 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 except as follows:
Modification:
Delete the third paragraph.
Note 2 of 3.7.22 is not applicable.
Addition:
3.1.101
auto-transformer
transformer in which input and output windings have a common part
NOTE 1 Auto-transformers may have supplementary windings (see Figure 101) or tappings (see Figure 102) for
adjustment purposes.
NOTE 2 Transformers with windings separated at least by functional insulation and electrically connected, will be
treated as auto-transformers (see Figure 103).

– 8 – 61558-2-13 © IEC:2009
IEC  243/09 IEC  244/09 IEC  245/09

Figure 101 – Windings Figure 102 – Tappings Figure 103 – Windings
separated by functional
isolation
3.5.101
core power
power transformed by the core, if this core was used in a transformer with separate windings
at the same supply voltage, output voltage, frequency, power factor and thermal
characteristics.
4 General requirements
This clause of Part 1 is applicable.
5 General notes on tests
This clause of Part 1 is applicable.
6 Ratings
Replacement:
6.101 The rated output voltage shall not exceed 1 000 V a.c. or 1 415 V ripple-free d.c. For
independent transformers, the rated output voltage shall exceed 50 V a.c. or 120 V ripple-
free d.c.
6.102 The rated output shall not exceed:
– 40 kVA for single-phase transformers;
– 200 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.
6.105 The core power shall not exceed:
– 2 kVA for single-phase transformers;

61558-2-13 © IEC:2009 – 9 –
– 10 kVA for polyphase transformers.
Transformers without limitation of the core power shall be subject to agreement between the
purchaser and the manufacturer.
The relation between the core power and the rated output is given in the following formula:
V - V
max min
Core power (VA) =   × rated output (VA)
V
max
where V and V are the highest and lowest values (rated supply voltage or rated
max min
output voltage).
NOTE In this case, the limitation of the core power is applicable to the rated output.
This formula is not applicable to a transformer with separate windings which are electrically
connected (see Figure 103). In this case, the core power of the transformer is equal to the
rated output.
Compliance with the requirements of 6.101 to 6.105 is checked by inspection of the marking.
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:
The transformers shall be marked with one of the graphical symbols shown in 8.11;
8.11 Addition:
Symbol or graphical symbol Explanation or title Identification
Fail-safe auto-transformer
60417-5941
or
F
F
Non-short-circuit proof auto-transformer
60417-5942
or
Short-circuit proof auto-transformer (inherently or
60417-5943
non-inherently)
or
– 10 – 61558-2-13 © IEC:2009
Addition:
8.101 If there is a terminal for connection to the star point, the maximum current to the star
point shall be marked.
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 exceed for independent transformers 50 V a.c.
or 120 V ripple-free d.c. but not exceed 1 000 V a.c. or 1 415 V ripple-free d.c.
For independent transformers, this output voltage limitation applies even when output
windings, not intended for interconnection, are connected in series.
NOTE An auto-transformer may have more than one output winding for adjustment reasons.
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 (%)
U
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.

61558-2-13 © IEC:2009 – 11 –
Table 101 – Output voltage difference
Type of auto-transformer Difference between no-load output voltage
Rated output and output voltage under load
VA %
Inherently short-circuit-proof auto-transformers:
– up to and including 63 100
– over 63 VA up to and including 630 50
– over 630 20
Other auto-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.
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 except as follows:
Modification:
18.2 Table 7: values between input circuits and output circuits, between each input
circuit and all other input circuits, between each output circuits and all other output
circuits are not applicable.
18.3 Table 8a: lines 1) and 2) are not applicable.

– 12 – 61558-2-13 © IEC:2009
19 Construction
This clause of Part 1 is applicable except as follows:
Addition:
19.106 Plug connected auto-transformers where the rated input voltage is higher than the
rated output voltage, shall not have any potential to earth at the output socket higher than
the rated output voltage.
This requirement shall be fulfilled by using one of the following methods.
19.106.1 Polarised input and output plug and socket-outlet system
In this case, an instruction shall be given for not using such a transformer with a non-
polarised plug and socket-outlet system.
19.106.2 Polarity detecting device (for non polarised input and output plug and socket-outlet
system)
A polarity detecting device shall only energise the output circuit when the potential to earth at
the poles of the output socket does not exceed the rated output voltage. The contact
separation of the breaking device shall be at least of 3 mm in each pole.
NOTE A magnetic relay is an example of polarity detecting device.
Compliance is checked by the following test.
The auto-transformer is connected to the mains at 1,06 times the rated input voltage under
the most unfavourable condition of load and output voltage. The test is repeated with the
polarity of the input reversed. During the test, the measured potential to earth of each pole
shall not exceed the maximum output voltage under load (1,06 times the rated output
voltage taking into account the permissible deviations of Clause 11).
Compliance is checked by measurement.
If the polarity detecting device uses a current flowing to the earth for the detection, this
current shall not exceed 0,75 mA and shall only be flowing for the period of measurement until
the polarity is reversed.
Compliance is checked by measurement.
All the tests are repeated under the fault conditions of H.2 of Annex H of Part 1. In this case
the potential to earth of each pole shall not exceed 1,06 times the maximum output voltage
under load for more than 5 s.
Compliance is checked by measurement.
19.111 Protection against direct contact with the live parts (contact path and drive) shall be
ensured.
Compliance is checked by inspection.
20 Components
This clause of Part 1 is applicable.

61558-2-13 © IEC:2009 – 13 –
21 Internal wiring
This clause of Part 1 is applicable.
22 Supply connection and other external flexible cable or cords
This clause of Part 1 is applicable.
23 Terminals for external conductors
This clause of Part 1 is applicable.
24 Provisions for protective earthing
This clause of Part 1 is applicable.
25 Screws and connections
This clause of Part 1 is applicable.
26 Creepage distances, clearances and distances through insulation
This clause of Part 1 is applicable except as follows:
Addition:
26.101 The values for creepage distances, clearances and distances through insulation for
working voltages above 1 000 V may be found by extrapolation.
27 Resistance to heat, fire and tracking
This clause of Part 1 is applicable.
28 Resistance to rusting
This clause of Part 1 is applicable.

– 14 – 61558-2-13 © IEC:2009
Annexes
The annexes of Part 1 are applicable except as follows:

Annex C
Creepage distances (cr), clearances (cl) and distances through
insulation (dti) Material group II (400 ≤CTI <600)

This annex of Pa
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