IEC 61558-2-16:2009

Safety of transformers, reactors, power supply units and similar products for supply voltages up to 1 100 V - Part 2-16: Particular requirements and tests for switch mode power supply units and transformers for switch mode power supply units

IEC 61558-2-16:2009 deals with the safety of switch mode power supply units and transformers for switch mode power supply units. Transformers incorporating electronic circuits are also covered by this standard. This Part 2-16 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 first edition of IEC 61558-2-16 cancels and replaces IEC 61558-2-17, published in 1997. It constitutes a technical revision. 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.

Sécurité des transformateurs, bobines d'inductance, blocs d'alimentation et produits analogues pour des tensions d'alimentation jusqu'à 1 100 V - Partie 2-16: Règles particulières et essais pour les blocs d'alimentation à découpage et les transformateurs pour blocs d'alimentation à découpage

La CEI 61558-2-16:2009 traite de la sécurité des blocs d'alimentation à découpage et des transformateurs pour blocs d'alimentation à découpage. Les transformateurs incorporant des circuits électroniques sont également couverts par la présente norme. La présente partie est destinée à être utilisée avec la dernière édition de la CEI 61558-1 et ses amendements. Elle est issue de la seconde édition (2005) de cette norme. Cette première édition de la CEI 61558-2-16 annule et remplace la CEI 61558-2-17 (1997). Elle constitue une révision technique. La présente partie a le statut de publication groupée de sécurité conformément au guide CEI 104 (1997): Elaboration des publications de sécurité et utilisation des publications fondamentales de sécurité et publications groupées de sécurité.

General Information

• Status: Published
• Publication Date: 16-Jun-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: 08-Jun-2021
• Completion Date: 05-Jul-2019

Relations

• Replaces: IEC 61558-2-17:1997 - Safety of power transformers, power supply units and similar - Part 2: Particular requirements for transformers for switch mode power supplies
• Effective Date: 05-Sep-2023
• Amended By: IEC 61558-2-16:2009/AMD1:2013 - Amendment 1 - Safety of transformers, reactors, power supply units and similar products for supply voltages up to 1 100 V - Part 2-16: Particular requirements and tests for switch mode power supply units and transformers for switch mode power supply units
• Effective Date: 05-Sep-2023
• Revised: IEC 61558-2-16:2021 - Safety of transformers, reactors, power supply units and combinations thereof - Part 2-16: Particular requirements and tests for switch mode power supply units and transformers for switch mode power supply units for general applications
• Effective Date: 05-Sep-2023

Overview

IEC 61558-2-16:2009 is an international standard published by the International Electrotechnical Commission (IEC) focusing on the safety requirements for switch mode power supply (SMPS) units and transformers used within these units. It applies to products designed for supply voltages up to 1,100 V. This standard forms Part 2-16 of the IEC 61558 series, providing particular requirements and test methods tailored for SMPS units and their associated transformers, including those incorporating electronic circuits.

IEC 61558-2-16 is intended to be used in conjunction with IEC 61558-1, which covers general safety requirements for transformers and power supply units. It supersedes the earlier IEC 61558-2-17 standard from 1997 and includes the latest technical revisions to address evolving technologies and safety concerns in electronic power supplies.

This standard holds the status of a group safety publication according to IEC Guide 104, facilitating a harmonized approach to safety in the design and testing of these devices globally.

---

Key Topics

Scope and Application

• Safety of switch mode power supply units and transformers for SMPS
• Inclusion of transformers with integrated electronic circuitry
• Compliance for supply voltages up to 1,100 V

General and Specific Safety Requirements

• Protection against electric shock
• Insulation resistance and dielectric strength
• Construction and component quality requirements
• Mechanical strength and resistance to environmental factors (dust, moisture, corrosion)
• Short-circuit and overload protection standards

Testing Protocols

• Verification of output voltage and current under load conditions
• No-load output voltage tests
• Short circuit voltage and heating tests
• Insulation and leakage current measurements
• Tests for creepage and clearance distances to prevent electrical breakdowns
• Resistance to heat, fire, tracking, and rusting

Marking and Information

• Clear labeling guidelines for safe use
• Instructions on handling input voltage setting changes

Annexes and Additional Guidance

• Normative references for insulated winding wires
• Partial discharge testing for insulation integrity
• Specific requirements for transformers operating at internal frequencies above 500 Hz

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Applications

IEC 61558-2-16 is essential for manufacturers, designers, and testing laboratories involved in the development and certification of switch mode power supply units and their transformers. These devices are widely used in:

• Consumer electronics requiring stabilized power supplies
• Industrial control and automation systems
• Telecommunications equipment
• Computing and IT hardware
• Medical devices where safety and reliability are critical
• Renewable energy systems and inverter technologies

By adhering to this standard, manufacturers ensure their SMPS products meet international safety requirements, reducing risks related to electrical shock, fire hazards, and operational failures. It also facilitates regulatory compliance and market access across different regions worldwide.

---

Related Standards

• IEC 61558-1: General requirements for safety of transformers, reactors, and power supply units
• IEC 60664-4: Insulation coordination regarding clearance and creepage distances for high-frequency circuits
• IEC Guide 104: Preparation of safety publications including basic and group safety publications
• IEC 61558-2-17: Previous edition relating to SMPS units and transformers, superseded by IEC 61558-2-16
• ISO/IEC Directives: Framework for drafting international standards

These standards collectively support the design, testing, and certification processes for electrical transformers and switch mode power supplies to meet stringent safety and performance criteria.

---

By complying with IEC 61558-2-16:2009, manufacturers and engineers can confidently develop safe, reliable, and efficient switch mode power supply units that conform to global safety benchmarks, enhancing product quality and user safety in electrical and electronic applications.

Standards Content (Sample)

IEC 61558-2-16 ®
Edition 1.0 2009-06
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 2-16: Particular requirements and tests for switch mode power supply units
and transformers for switch mode power supply units

Sécurité des transformateurs, bobines d’inductance, blocs d'alimentation et
produits analogues pour des tensions d’alimentation jusqu'à 1 100 V –
Partie 2-16: Règles particulières et essais pour les blocs d'alimentation à
découpage et les transformateurs pour blocs d'alimentation à découpage

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IEC 61558-2-16 ®
Edition 1.0 2009-06
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 2-16: Particular requirements and tests for switch mode power supply units
and transformers for switch mode power supply units

Sécurité des transformateurs, bobines d’inductance, blocs d'alimentation et
produits analogues pour des tensions d’alimentation jusqu'à 1 100 V –
Partie 2-16: Règles particulières et essais pour les blocs d'alimentation à
découpage et les transformateurs pour blocs d'alimentation à découpage

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
V
CODE PRIX
ICS 29.180 ISBN 978-2-88910-543-4
– 2 – 61558-2-16 © IEC:2009
CONTENTS
FOREWORD.4
1 Scope.6
2 Normative references.8
3 Terms and definitions .9
4 General requirements .9
5 General notes on tests.9
6 Ratings.9
7 Classification .10
8 Marking and other information.10
9 Protection against electric shock.11
10 Change of input voltage setting .12
11 Output voltage and output current under load .12
12 No-load output voltage.12
13 Short circuit voltage .13
14 Heating.13
15 Short-circuit and overload protection .13
16 Mechanical strength.14
17 Protection against harmful ingress of dust, solid objects and moisture.14
18 Insulation resistance, dielectric strength and leakage current .14
19 Construction .14
20 Components .18
21 Internal wiring .18
22 Supply connection and other external flexible cables or cords.19
23 Terminals for external conductors .19
24 Provisions for protective earthing .19
25 Screws and connections .19
26 Creepage distances, clearances and distances through insulation .19
27 Resistance to heat, fire and tracking .32
28 Resistance to rusting .32
Annexes.33
Annex AA (informative) Partial discharge (PD) test .33
Annex BB (normative) Particular requirements for associated transformers for use in
switch mode power supplies with internal frequencies > 500 Hz .33

Figure 101 – Diagram for dimensioning of clearances.20
Figure 102 – Diagram of dimensioning creepage distances.24
Figure 103 – Permissible field strength for dimensioning of solid insulation according to
Equation (1) .32

Table 101 – Output voltages ratio.13
Table 102 – Values of clearances for frequencies > 30 kHz with approximately
homogeneous field condition according to 4.3 of IEC 60664-4 .21

61558-2-16 © IEC:2009 – 3 –
Table 103 – Values of clearances for transient overvoltages or recurring peak voltages
produced in the primary circuit of the SMPS for frequencies < 30 kHz.22
Table 104 – Minimum values of clearances in air for inhomogeneous field conditions for
frequency > 30 kHz .
Table 105 – Basic or supplementary insulation – Minimum values of creepage distances
for different frequency ranges (pollution degree 1).25
Table 106 – Basic or supplementary insulation – Minimum values of creepage distances
for different frequency ranges (pollution degree 2).26
Table 107 – Basic or supplementary insulation – Minimum values of creepage distances
for different frequency ranges (pollution degree 3).27
Table 108 – Double or reinforced insulation – Minimum values of creepage distances for
different frequency ranges (pollution degree 1) .28
Table 109 – Double or reinforced insulation – Minimum values of creepage distances for
different frequency ranges (pollution degree 2) .29
Table 110 – Double or reinforced insulation – Minimum values of creepage distances for
different frequency ranges (pollution degree 3) .30

– 4 – 61558-2-16 © IEC:2009
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF TRANSFORMERS, REACTORS, POWER SUPPLY UNITS
AND SIMILAR PRODUCTS FOR SUPPLY VOLTAGES UP TO 1 100 V –

Part 2-16: Particular requirements and tests for switch mode power supply
units and transformers for switch mode power supply units

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,
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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
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3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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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
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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 61558-2-16 has been prepared by IEC technical committee 96:
Transformers, reactors, power supply units and similar products for low voltage up to 1 100 V.
This first edition of IEC 61558-2-16 cancels and replaces IEC 61558-2-17, published in 1997. It
constitutes a technical revision.
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.
61558-2-16 © IEC:2009 – 5 –
The text of this standard is based on the following documents:
FDIS Report on voting
96/330/CDV 96/333/RVC
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 2-16 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 switch mode power
supply units and transformers for switch mode power supply units.
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 – 61558-2-16 © IEC:2009
SAFETY OF TRANSFORMERS, REACTORS, POWER SUPPLY UNITS
AND SIMILAR PRODUCTS FOR SUPPLY VOLTAGES UP TO 1 100 V –

Part 2-16: Particular requirements and tests for switch mode power supply
units and transformers for switch mode power supply units

1 Scope
Replacement:
This part of IEC 61558 deals with the safety of switch mode power supply units and
transformers for switch mode power supply units. Transformers incorporating electronic
circuits are also covered by this standard.
NOTE 1 Safety includes electrical, thermal and mechanical aspects.
This part applies to:
a) switch mode power supply units incorporating safety isolating transformers providing
SELV, PELV or FELV a.c. or d.c. output voltage(s), or a combination thereof according to
IEC 61140 and IEC 60364-4-41 for use with household and other consumer products,
except for products covered by IEC 60065, IEC 61347 series, IEC 61204-7 and IEC 60950-
1;
b) switch mode power supply units with a maximum output voltage not exceeding 1 000 V
a.c. or 1 414 V ripple-free d.c. for use with household and other consumer products, except
for products covered in a) and products covered by IEC 60065, IEC 61347 series,
IEC 61204-7 and IEC 60950-1;
c) this standard may be used for transformers for use in switch mode power supply units
(see Annex BB).
This part covers the safety requirements for:
• separating SMPS for general use corresponding to Part 2-1;
• isolating SMPS for general use corresponding to Part 2-4;
• safety isolating SMPS for general use corresponding to Part 2-6;
• auto-SMPS for general use corresponding to Part 2-13.
For SMPS for specific application corresponding to the other Parts 2 of 61558 series, the
necessary requirements of the relevant Parts 2 are applicable. In addition, the requirements
listed in this part apply. Where the two requirements are in conflict, the most severe take
precedence.
NOTE 2 As the maximum rated supply voltage of the internal transformer is 1 000 V, the maximum rated
supply voltage of the switch mode power supply may be lower due to type of rectification.
Switch mode power supply units covered by this standard are air cooled (natural or forced)
independent, associated, stationary, portable, single-phase, or polyphase, with the rated
supply voltage not exceeding 1 100 V a.c., the rated supply frequency not exceeding
500 Hz, the rated internal operating frequency exceeding 500 Hz, but not exceeding
100 MHz, and the rated output not exceeding 1 kVA or 1 kW, incorporating dry-type
transformers with encapsulated or non-encapsulated windings.

61558-2-16 © IEC:2009 – 7 –
Associated transformers for switch mode power supply units covered by Annex BB of this
standard shall have a rated output not exceeding:
– 25 kVA for single-phase transformers;
– 40 kVA for polyphase transformers.
NOTE 3 For higher frequencies, additional requirements may be necessary. However, this standard may be used
as a guide.
The no-load output voltage or the rated output voltage of switch mode power supply
units shall not exceed:
– 1 000 V a.c. or 1 415 V ripple-free d.c. when separating transformers or auto-
transformers are used;
– 500 V a.c. or 708 V ripple-free d.c. when isolating transformers are used;
– 50 V a.c. or 120 V ripple-free d.c. when safety isolating transformers are used.
The no-load output voltage or the rated output voltage of independent switch mode
power supply units shall not be less than:
– 50 V a.c. or 120 V ripple-free d.c. when separating transformers or autotransformers are
used.
This standard is also applicable to switch mode power supply units, converters and inverters
without limitation of the rated output. However, such switch mode power supply units are
for special applications and are subject to an agreement between the purchaser and the
manufacturer.
NOTE 4 In the context of this standard, converters and invertors are considered to be switch mode power supply
units.
This standard may also be used as a guide for products not covered by the scope of this
standard, the scope of IEC 61204-7, or the scope of IEC 61347 series.
This standard does not apply to:
– motor-generator sets;
– uninterruptible power supplies (UPS) according to IEC 62040;
– switch mode power supply units covered by IEC 61204-7 (i.e., low-voltage power supply
devices, d.c. output, performance characteristics) and d.c. power and distribution
equipment and switch mode power supply units for use in applications covered by
IEC 60950-1, IEC 61010-1, IEC 60601-1, and IEC 60065;
– lamp control gear covered by IEC 61347-1;
– external circuits and their components intended to be connected to the input terminals and
output terminals of the transformers.
NOTE 5 IEC 61204-7 will be updated by SC 22E.
NOTE 6 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;
– 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, such as tropical environment.

– 8 – 61558-2-16 © IEC:2009
NOTE 7 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.
Unless otherwise specified, from here onward, the term SMPS covers switch mode power
supply units.
2 Normative references
This clause of Part 1 is applicable, except as follows:
Addition:
IEC 60227 (all parts), Polyvinyl chloride insulated cables of rated voltages up to and including
450/750 V
IEC 60364-4-41, Low-voltage electrical installations – Part 4-41: Protection for safety –
Protection against electric shock
IEC 60950-1, Information technology equipment – Safety – Part 1:General requirements
IEC 60601-1, Medical electrical equipment – Part 1:General requirements for basic safety and
essential performance
IEC 60664-4:2005, Insulation coordination for equipment within low-voltage systems – Part 4:
Consideration of high-frequency voltage stress
IEC 61010-1, Safety requirements for electrical equipment for measurement, control, and
laboratory use – Part 1:General requirements
IEC 61204-7:2006, Low voltage power supplies, d.c. output – Part 7:Safety requirements
IEC 61347 (all parts), Lamp controlgear
IEC 61558-1:2005, Safety of power transformers, power supplies, reactors and similar products
– Part 1: General requirements and tests
IEC 61558-2-1, Safety of power transformers, power supplies, reactors and similar products –
Part 2-1: Particular requirements and tests for separating transformers and power supplies
incorporating separating transformers for general applications
IEC 61558-2-4, Safety of transformers, reactors, power supply units and similar products for
supply voltages up to 1 100 V – Part 2-4: Particular requirements and tests for isolating
transformers and power supply units incorporating isolating transformers
IEC 61558-2-6, 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 61558-2-13, 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 62040 (all parts), Uninterruptible power systems (UPS)

61558-2-16 © IEC:2009 – 9 –
3 Terms and definitions
This clause of Part 1 is applicable, except as follows:
Addition:
The term transformer in Part 1 also designates a SMPS as defined by this part.
In Annex BB of this standard, the term transformer applies to a transformer for SMPS.
In this standard, the actual applicable terms are used.
Replacement
3.3.8
working voltage
highest r.m.s. value of the a.c. or d.c. voltage which may occur (locally) across any insulation
at rated supply voltage under no-load or normal operating conditions, transients being
disregarded. The working voltage between any point in the circuit supplied by the mains and
other isolated parts shall be assumed:
• the rated input voltage, or
• the measured working voltage
whichever is greater
NOTE 1 When considering the insulation system between windings not intended to be connected together, the
working voltage is considered to be the highest voltage occurring on any of these windings.
NOTE 2 On three phase systems, the working voltage can be different from the nominal voltage.
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:
– 1 000 V a.c. or 1 415 V ripple-free d.c. for SMPS incorporating separating transformers or
auto-transformers;
– 500 V a.c. or 708 V ripple-free d.c. for SMPS incorporating isolating transformers;
– 50 V a.c. or 120 V ripple-free d.c. for SMPS incorporating safety isolating transformers.

– 10 – 61558-2-16 © IEC:2009
For independent SMPS incorporating separating transformers or auto-transformers, the
rated output voltage shall exceed 50 V a.c. or 120 V ripple-free d.c. and not exceed 1 000 V
a.c. or 1 415 V ripple-free d.c.
6.102 The rated output of the SMPS shall not exceed 1 kVA or 1 kW.
NOTE See Annex BB for a transformer incorporated in an SMPS.
6.103 The rated supply frequency shall not exceed 500 Hz.
6.104 The rated internal operating frequency shall not exceed 100 MHz.
6.105 The rated supply voltage shall not exceed 1 100 V a.c.
Compliance with 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:
relevant graphical symbols shown in 8.11 indicating the kind of transformer in addition with the
symbol for SMPS; if an IP00 transformer or and associated transformers have circuits
corresponding to different parts 2 in the same construction (e.g. SELV output circuit
according to Part 2-6 and 230 V output circuit according to Part 2-4) the relevant symbols
have to be used. The term transformer shall be replaced by SMPS, except for the marking
which applies to incorporated transformers and incorporated SMPS;
8.11 Addition:
The following symbols shall be used to indicate the type of transformer(s) that are
incorporated:
61558-2-16 © IEC:2009 – 11 –
Symbol or graphical Explanation or title Identification
symbol
SMPS incorporating a
or
F
F
fail-safe separating transformer

SMPS incorporating a IEC 60417-5223

(2002-10)
or
non-short-circuit-proof separating transformer

SMPS incorporating a
IEC 60417-5220
or (2002-10)
short-circuit-proof separating transformer

(inherently or non-inherently)
SMPS incorporating a
or
F F
fail-safe isolating transformer

SMPS incorporating a
or
non-short-circuit-proof isolating transformer

SMPS incorporating a
or
short-circuit-proof isolating transformer

(inherently or non-inherently)
SMPS incorporating a
fail-safe safety isolating transformer
F
SMPS incorporating a
non-short-circuit-proof safety isolating
transformer
SMPS incorporating a
short-circuit-proof safety isolating transformer

(inherently or non-inherently)
SMPS incorporating a
or
F
F
fail-safe auto-transformer
SMPS incorporating a
or
non-short-circuit proof auto-transformer

SMPS incorporating a
or
short-circuit proof auto-transformer (inherently or

non-inherently)
S
SMPS (Switch mode power supply unit)

9 Protection against electric shock
This clause of Part 1 is applicable.

– 12 – 61558-2-16 © IEC:2009
10 Change of input voltage setting
This clause of Part 1 is applicable except as follows:
Addition:
10.101 A wide range (e.g. 100 V a.c. to 240 V a.c.) of supply voltage is allowed if the output
voltage does not exceed the rated output voltage and the no-load output voltage does not
exceed the limits of the output voltage deviation according to the type of transformer feeding
the appropriate output circuit.
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 SMPS 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:
– 1 000 V a.c. or 1 415 V ripple-free d.c. for SMPS incorporating separating transformers or
auto-transformers;
– 500 V a.c. or 708 V ripple-free d.c. for SMPS incorporating isolating transformers;
– 50 V a.c. or 120 V ripple-free d.c. for SMPS incorporating safety isolating transformers.
For independent transformers, this output voltage limitation applies even when output
windings, not intended for interconnection, are connected in series.
12.102 The difference between the no-load output voltage and the output voltage under
rated load shall not be excessive.
The difference between the no-load output voltage measured in this clause and the output
voltage under load measured during the test of Clause 11, expressed as a percentage of the
latter voltage, shall not exceed the values shown in Table 101.
U – U
no-load load
NOTE 1 The ratio is defined as follows:      × 100 %
U
load
where U is the no-load output voltage and U is the output voltage under load.

no-load load
61558-2-16 © IEC:2009 – 13 –
Table 101 – Output voltages ratio
Type of transformer Ratio between no-load output voltage and output
Rated output voltage under load
VA %
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
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 SMPS is connected to the rated supply
voltage at the rated supply frequency.
The difference shall not exceed the values shown in Table 101.
NOTE 2 The values of Table 101 are based on the values of Part 2-4 and are also applicable to SMPS according
to Part 2-1, 2-6, and 2-13.
12.103 Unless otherwise specified by the manufacturer, SMPS with high frequency output
rating shall be tested with 20 cm to 200 cm length of wire connected to the output terminals
under the most unfavourable conditions. Two twisted wires or cables rated 60227 IEC 53 may
be used. The cross sectional area of the conductors shall be determined according to the rated
output of the SMPS, and the current density shall not exceed 5 A/mm in normal use.
13 Short circuit voltage
This clause of Part 1 is applicable.
14 Heating
This clause of Part 1 is applicable, except as follows:
Addition:
14.101 For SMPS incorporating transformers with internal frequencies higher than 1 kHz,
thermocouples or equivalent means of measuring the temperatures may be used to determine
the temperature of the windings and the insulating materials.
The maximum values of Table 1 in Part 1 for winding temperatures shall be reduced by 10 °C
for the thermocouple measurements. The thermocouples shall be mounted only on accessible
surfaces of the incorporated transformers.
NOTE The thermo-couples should not be integrated in the windings.
15 Short-circuit and overload protection
This clause of Part 1 is applicable, except as follows:
Addition:
15.101 Electronic circuits shall be so designed and applied that a fault condition within the
SMPS will not cause electric shock, or fire hazard, and unintentional operation of the appliance
will not impair safety.
– 14 – 61558-2-16 © IEC:2009
Compliance is checked by evaluation of the fault condition specified in Annex H of Part 1.
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.
18.3 Addition of a new box 5 for Table 8a:
Table 8a – Table of dielectric strength test voltages
Working voltage
Application of dielectric strength test voltage V
<50 150 300 600 1 000
5) Over functional insulation for windings intended
to be connected in series or parallel Working voltage + 500 V
18.4 does not apply.
Addition:
The term transformer shall be replaced by SMPS where applicable.
18.101 SMPS shall fulfil the impulse test according to Table F.5 of IEC 60664-1 with 1,2/50
μs as follows:
After the test of 18.3, the SMPS shall be connected to the impulse test equipment. The impulse
test shall be carried out with 10 impulses of each polarity between the input and output
terminals of the SMPS. The interval between the impulses shall be at least 1 s if the impulses
are produced inside the SMPS.
During the test, there shall be no breakdown of the insulation between turns of a winding,
between input and output circuits, between adjacent input or output circuits, or between
the windings and any conductive core.
19 Construction
This clause of Part 1 is applicable, except as follows:
19.1 Replacement:
19.1.1 SMPS incorporating auto-transformers
19.1.1.1 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.
61558-2-16 © IEC:2009 – 15 –
This requirement shall be fulfilled by using one of the following methods:
19.1.1.2 Polarized 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.
19.1.1.3 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.2.3 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.
19.1.2 SMPS incorporating separating transformers
19.1.2.1 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.
19.1.2.2 The insulation between the input and output winding(s) shall consist of at least
basic insulation.
In addition, the following requirements apply:
– for class I SMPS, the insulation between the input windings and the body, and between
the output windings and the body shall consist of at least basic insulation (both basic
insulations rated for the working voltage);

– 16 – 61558-2-16 © IEC:2009
– for class II SMPS, the insulation between the input windings and the body, and between
the output windings and the body shall consist of double or reinforced insulation (both
double or reinforced insulations rated for the working voltage).
19.1.2.3 For SMPS with intermediate conductive parts (e.g., the iron core) or a resonant
circuit, not connected to the body and located between the input and output windings, the
insulation between the intermediate conductive parts (or a resonant circuit) and the input
windings or between the intermediate conductive parts (or a resonant circuit) and the output
windings shall consist of at least basic insulation.
NOTE An intermediate conductive part (or a resonant circuit), 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).
In addition, the following requirements apply:
– for class I SMPS, the insulation between the input and output windings via the
intermediate conductive parts (or a resonant circuit) shall consist of at least basic
insulation (rated for the working voltage);
– for class II SMPS, the insulation between the input windings and the body, and between
the output windings and the body, via the intermediate conductive parts (or a resonant
circuit) shall consist of double or reinforced insulation (rated for the input and output
voltage).
19.1.2.4 Parts of output circuits may be connected to protective earth.
19.1.2.5 There shall be no direct connection between the output circuits and the body,
unless – for associated transformers - allowed by the relevant equipment standard, or 19.8
of Part 1 is fulfilled. However, capacitors according to 19.8 are allowed.
Compliance is checked by inspection.
19.1.3 SMPS incorporating isolating transformers and safety isolating transformers
19.1.3.1 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, 19, and 26 into
consideration.
19.1.3.2 The insulation between input and output winding(s) shall consist of double or
reinforced insulation (rated for the working voltage), unless the requirements in 19.1.3.4 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);

61558-2-16 © IEC:2009 – 17 –
– 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 volt
...

IEC 61558-2-16 ®
Edition 1.1 2013-08
CONSOLIDATED
VERSION
VERSION
CONSOLIDÉE
colour
inside
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 2-16: Particular requirements and tests for switch mode power supply units
and transformers for switch mode power supply units

Sécurité des transformateurs, bobines d’inductance, blocs d'alimentation et
produits analogues pour des tensions d’alimentation jusqu'à 1 100 V –
Partie 2-16: Règles particulières et essais pour les blocs d'alimentation à
découpage et les transformateurs pour blocs d'alimentation à découpage

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IEC 61558-2-16 ®
Edition 1.1 2013-08
CONSOLIDATED
VERSION
VERSION
CONSOLIDÉE
colour
inside
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 2-16: Particular requirements and tests for switch mode power supply units

and transformers for switch mode power supply units

Sécurité des transformateurs, bobines d’inductance, blocs d'alimentation et

produits analogues pour des tensions d’alimentation jusqu'à 1 100 V –

Partie 2-16: Règles particulières et essais pour les blocs d'alimentation à

découpage et les transformateurs pour blocs d'alimentation à découpage

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.180 ISBN 978-2-8322-1043-7

IEC 61558-2-16 ®
Edition 1.1 2013-08
REDLINE VERSION
VERSION REDLINE
colour
inside
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 2-16: Particular requirements and tests for switch mode power supply units
and transformers for switch mode power supply units

Sécurité des transformateurs, bobines d’inductance, blocs d'alimentation et
produits analogues pour des tensions d’alimentation jusqu'à 1 100 V –
Partie 2-16: Règles particulières et essais pour les blocs d'alimentation à
découpage et les transformateurs pour blocs d'alimentation à découpage

– 2 – 61558-2-16  IEC:2009+A1:2013

CONTENTS
FOREWORD . 4

INTRODUCTION TO THE AMENDMENT . 6

1 Scope . 7

2 Normative references. 9

3 Terms and definitions . 10

4 General requirements . 11

5 General notes on tests . 11
6 Ratings . 11
7 Classification . 11
8 Marking and other information . 11
9 Protection against electric shock . 13
10 Change of input voltage setting . 14
11 Output voltage and output current under load . 14
12 No-load output voltage . 14
13 Short circuit voltage . 15
14 Heating . 15
15 Short-circuit and overload protection . 15
16 Mechanical strength . 16
17 Protection against harmful ingress of dust, solid objects and moisture . 16
18 Insulation resistance, dielectric strength and leakage current . 16
19 Construction . 17
20 Components . 24
21 Internal wiring . 24
22 Supply connection and other external flexible cables or cords. 24
23 Terminals for external conductors . 24
24 Provisions for protective earthing . 24
25 Screws and connections . 24
26 Creepage distances, clearances and distances through insulation . 24
27 Resistance to heat, fire and tracking . 40

28 Resistance to rusting . 40

Annexes . 41
Annex K (normative) Insulated winding wires . 41
Annex AA (informative) Partial discharge (PD) test . 44
Annex BB (normative) Particular requirements for associated transformers for use in
switch mode power supplies with internal frequencies > 500 Hz . 44

Bibliography . 46

Figure 101 – Diagram for dimensioning of clearances . 26
Figure 102 – Diagram of dimensioning creepage distances . 29

61558-2-16  IEC:2009+A1:2013 – 3 –

Figure 103 – Permissible field strength for dimensioning of solid insulation according to

Equation (1) . 37

Figure 104 – Test voltages . 17

Table 101 – Output voltages ratio . 15

Table 102 – Values of clearances for frequencies > 30 kHz with approximately

homogeneous field condition according to 4.3 of IEC 60664-4 . 26

Table 103 – Values of clearances for transient overvoltages or recurring peak voltages

produced in the primary circuit of the SMPS for frequencies < 30 kHz . 27

Table 104 – Minimum values of clearances in air for inhomogeneous field conditions for
frequency > 30 kHz . 27
Table 105 – Basic or supplementary insulation – Minimum values of creepage distances
for different frequency ranges (pollution degree 1) . 30
Table 106 – Basic or supplementary insulation – Minimum values of creepage distances
for different frequency ranges (pollution degree 2) . 31
Table 107 – Basic or supplementary insulation – Minimum values of creepage distances
for different frequency ranges (pollution degree 3) . 32
Table 108 – Double or reinforced insulation – Minimum values of creepage distances for
different frequency ranges (pollution degree 1) . 33
Table 109 – Double or reinforced insulation – Minimum values of creepage distances for
different frequency ranges (pollution degree 2) . 34
Table 110 – Double or reinforced insulation – Minimum values of creepage distances for
different frequency ranges (pollution degree 3) . 35
Table 111 – Values of FIW wires with maximum overall diameter and minimum test
voltages according to enamel increase . 39
Table K.1 – Mandrel diameter. 42
Table K.2 – Oven temperature . 42

– 4 – 61558-2-16  IEC:2009+A1:2013

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
SAFETY OF TRANSFORMERS, REACTORS, POWER SUPPLY UNITS

AND SIMILAR PRODUCTS FOR SUPPLY VOLTAGES UP TO 1 100 V –

Part 2-16: Particular requirements and tests for switch mode power supply

units and transformers for switch mode power supply units

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

This Consolidated version of IEC 61558-2-16 bears the edition number 1.1. It consists of
the first edition (2009) [documents 96/330/FDIS and 96/333/RVD] and its amendment 1
(2013) [documents 96/401/FDIS and 96/405/RVD]. The technical content is identical to the
base edition and its amendment.
In this Redline version, a vertical line in the margin shows where the technical content is
modified by amendment 1. Additions and deletions are displayed in red, with deletions
being struck through. A separate Final version with all changes accepted is available in
this publication.
This publication has been prepared for user convenience.

61558-2-16  IEC:2009+A1:2013 – 5 –

International Standard IEC 61558-2-16 has been prepared by IEC technical committee 96:

Transformers, reactors, power supply units and similar products for low voltage up to 1 100 V.

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

This Part 2-16 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 switch mode power
supply units and transformers for switch mode power supply units. 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 the base publication and its amendment will
remain unchanged until the stability 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.

IMPORTANT – The “colour inside” logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this publication using a colour printer.

– 6 – 61558-2-16  IEC:2009+A1:2013

INTRODUCTION TO THE AMENDMENT
This amendment has been prepared to allow the use of FIW wires in SMPS.

The manufacturer should be careful, that during production and transport no damage of the
FIW wire will be possible.
61558-2-16  IEC:2009+A1:2013 – 7 –

SAFETY OF TRANSFORMERS, REACTORS, POWER SUPPLY UNITS

AND SIMILAR PRODUCTS FOR SUPPLY VOLTAGES UP TO 1 100 V –

Part 2-16: Particular requirements and tests for switch mode power supply

units and transformers for switch mode power supply units

1 Scope
Replacement:
This part of IEC 61558 deals with the safety of switch mode power supply units and
transformers for switch mode power supply units. Transformers incorporating electronic
circuits are also covered by this standard.
NOTE 1 Safety includes electrical, thermal and mechanical aspects.
This part applies to:
a) switch mode power supply units incorporating safety isolating transformers providing
SELV, PELV or FELV a.c. or d.c. output voltage(s), or a combination thereof according to
IEC 61140 and IEC 60364-4-41 for use with household and other consumer products,
except for products covered by IEC 60065, IEC 61347 series, IEC 61204-7 and IEC 60950-
1;
b) switch mode power supply units with a maximum output voltage not exceeding 1 000 V
a.c. or 1 414 V ripple-free d.c. for use with household and other consumer products, except
for products covered in a) and products covered by IEC 60065, IEC 61347 series,
IEC 61204-7 and IEC 60950-1;
c) this standard may be used for transformers for use in switch mode power supply units
(see Annex BB).
This part covers the safety requirements for:
• separating SMPS for general use corresponding to Part 2-1;
• isolating SMPS for general use corresponding to Part 2-4;
• safety isolating SMPS for general use corresponding to Part 2-6;
• auto-SMPS for general use corresponding to Part 2-13.

For SMPS for specific application corresponding to the other Parts 2 of 61558 series, the
necessary requirements of the relevant Parts 2 are applicable. In addition, the requirements
listed in this part apply. Where the two requirements are in conflict, the most severe take
precedence.
NOTE 2 As the maximum rated supply voltage of the internal transformer is 1 000 V, the maximum rated
supply voltage of the switch mode power supply may be lower due to type of rectification.
Switch mode power supply units covered by this standard are air cooled (natural or forced)
independent, associated, stationary, portable, single-phase, or polyphase, with the rated
supply voltage not exceeding 1 100 V a.c., the rated supply frequency not exceeding
500 Hz, the rated internal operating frequency exceeding 500 Hz, but not exceeding
100 MHz, and the rated output not exceeding 1 kVA or 1 kW, incorporating dry-type
transformers with encapsulated or non-encapsulated windings.

– 8 – 61558-2-16  IEC:2009+A1:2013

Associated transformers for switch mode power supply units covered by Annex BB of this

standard shall have a rated output not exceeding:

– 25 kVA for single-phase transformers;

– 40 kVA for polyphase transformers.

NOTE 3 For higher frequencies, additional requirements may be necessary. However, this standard may be used
as a guide.
The no-load output voltage or the rated output voltage of switch mode power supply

units shall not exceed:
– 1 000 V a.c. or 1 415 V ripple-free d.c. when separating transformers or auto-
transformers are used;
– 500 V a.c. or 708 V ripple-free d.c. when isolating transformers are used;
– 50 V a.c. or 120 V ripple-free d.c. when safety isolating transformers are used.
The no-load output voltage or the rated output voltage of independent switch mode
power supply units shall not be less than:
– 50 V a.c. or 120 V ripple-free d.c. when separating transformers or autotransformers are
used.
This standard is also applicable to switch mode power supply units, converters and inverters
without limitation of the rated output. However, such switch mode power supply units are
for special applications and are subject to an agreement between the purchaser and the
manufacturer.
NOTE 4 In the context of this standard, converters and invertors are considered to be switch mode power supply
units.
This standard may also be used as a guide for products not covered by the scope of this
standard, the scope of IEC 61204-7, or the scope of IEC 61347 series.
This standard does not apply to:
– motor-generator sets;
– uninterruptible power supplies (UPS) according to IEC 62040;
– switch mode power supply units covered by IEC 61204-7 (i.e., low-voltage power supply
devices, d.c. output, performance characteristics) and d.c. power and distribution
equipment and switch mode power supply units for use in applications covered by
IEC 60950-1, IEC 61010-1, IEC 60601-1, and IEC 60065;

– lamp control gear covered by IEC 61347-1;
– external circuits and their components intended to be connected to the input terminals and
output terminals of the transformers.
NOTE 5 IEC 61204-7 will be updated by SC 22E.
NOTE 6 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;
– 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, such as tropical environment.

61558-2-16  IEC:2009+A1:2013 – 9 –

NOTE 7 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.

Unless otherwise specified, from here onward, the term SMPS covers switch mode power

supply units.
2 Normative references
This clause of Part 1 is applicable, except as follows:

Addition:
IEC 60227 (all parts), Polyvinyl chloride insulated cables of rated voltages up to and including
450/750 V
IEC 60317-0-7:2012, Specifications for particular types of winding wires – Part 0-7: General
requirements – Fully insulated (FIW) zero-defect enamelled round copper wire with nominal
conductor diameter of 0,040 mm to 1,600 mm
IEC 60317-43, Specifications for particular types of winding wires – Part 43: Aromatic polyimide
tape wrapped round copper wire, class 240
IEC 60317-56, Specifications for particular types of winding wires – Part 56: Solderable fully
insulated (FIW) zero-defect polyurethane enamelled round copper wire with nominal conductor
diameter 0,040 mm to 1,600 mm, class 180
IEC 60364-4-41, Low-voltage electrical installations – Part 4-41: Protection for safety –
Protection against electric shock
IEC 60601-1, Medical electrical equipment – Part 1:General requirements for basic safety and
essential performance
IEC 60664-4:2005, Insulation coordination for equipment within low-voltage systems – Part 4:
Consideration of high-frequency voltage stress
IEC 60851-3:2009, Winding wires – Test methods – Part 3: Mechanical properties
IEC 60851-5:2008, Winding wires – Test methods – Part 5: Electrical properties
IEC 60950-1, Information technology equipment – Safety – Part 1:General requirements

IEC 61010-1, Safety requirements for electrical equipment for measurement, control, and
laboratory use – Part 1:General requirements
IEC 61204-7:2006, Low voltage power supplies, d.c. output – Part 7:Safety requirements
IEC 61347 (all parts), Lamp controlgear
IEC 61558-1:2005, Safety of power transformers, power supplies, reactors and similar products
– Part 1: General requirements and tests
IEC 61558-2-1, Safety of power transformers, power supplies, reactors and similar products –
Part 2-1: Particular requirements and tests for separating transformers and power supplies
incorporating separating transformers for general applications

– 10 – 61558-2-16  IEC:2009+A1:2013

IEC 61558-2-4, Safety of transformers, reactors, power supply units and similar products for

supply voltages up to 1 100 V – Part 2-4: Particular requirements and tests for isolating

transformers and power supply units incorporating isolating transformers

IEC 61558-2-6, 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 61558-2-13, 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 62040 (all parts), Uninterruptible power systems (UPS)
3 Terms and definitions
This clause of Part 1 is applicable, except as follows:
Addition:
The term transformer in Part 1 also designates a SMPS as defined by this part.
In Annex BB of this standard, the term transformer applies to a transformer for SMPS.
In this standard, the actual applicable terms are used.
Replacement
3.3.8
working voltage
highest r.m.s. value of the a.c. or d.c. voltage which may occur (locally) across any insulation
at rated supply voltage under no-load or normal operating conditions, transients being
disregarded. The working voltage between any point in the circuit supplied by the mains and
other isolated parts shall be assumed:
• the rated input voltage, or
• the measured working voltage
whichever is greater
NOTE 1 When considering the insulation system between windings not intended to be connected together, the
working voltage is considered to be the highest voltage occurring on any of these windings.
NOTE 2 On three phase systems, the working voltage can be different from the nominal voltage.
Addition:
3.101
FIW
fully insulated winding wire
wire according to IEC 60317-0-7, IEC 60317-56 and IEC 60851-5:2008 which is a zero-defect
wire construction
3.102
zero-defect wire
winding wire that exhibits no electrical discontinuities when tested under specific conditions

61558-2-16  IEC:2009+A1:2013 – 11 –

3.103
grade of FIW
range of overall diameter of a wire (FIW3 – FIW9)

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:
– 1 000 V a.c. or 1 415 V ripple-free d.c. for SMPS incorporating separating transformers or
auto-transformers;
– 500 V a.c. or 708 V ripple-free d.c. for SMPS incorporating isolating transformers;
– 50 V a.c. or 120 V ripple-free d.c. for SMPS incorporating safety isolating transformers.
For independent SMPS incorporating separating transformers or auto-transformers, the
rated output voltage shall exceed 50 V a.c. or 120 V ripple-free d.c. and not exceed 1 000 V
a.c. or 1 415 V ripple-free d.c.
6.102 The rated output of the SMPS shall not exceed 1 kVA or 1 kW.
NOTE See Annex BB for a transformer incorporated in an SMPS.
6.103 The rated supply frequency shall not exceed 500 Hz.
6.104 The rated internal operating frequency shall not exceed 100 MHz.
6.105 The rated supply voltage shall not exceed 1 100 V a.c.

Compliance with 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:
– 12 – 61558-2-16  IEC:2009+A1:2013

relevant graphical symbols shown in 8.11 indicating the kind of transformer in addition with the

symbol for SMPS; if an IP00 transformer or and associated transformers have circuits

corresponding to different parts 2 in the same construction (e.g. SELV output circuit

according to Part 2-6 and 230 V output circuit according to Part 2-4) the relevant symbols

have to be used. The term transformer shall be replaced by SMPS, except for the marking

which applies to incorporated transformers and incorporated SMPS;

8.11 Addition:
The following symbols shall be used to indicate the type of transformer(s) that are

incorporated:
61558-2-16  IEC:2009+A1:2013 – 13 –

Symbol or graphical Explanation or title Identification
symbol
SMPS incorporating a
or
F
F
fail-safe separating transformer

SMPS incorporating a IEC 60417-5223

(2002-10)
or
non-short-circuit-proof separating transformer

SMPS incorporating a
IEC 60417-5220
or (2002-10)
short-circuit-proof separating transformer

(inherently or non-inherently)
SMPS incorporating a
or
F F
fail-safe isolating transformer

SMPS incorporating a
or
non-short-circuit-proof isolating transformer

SMPS incorporating a
or
short-circuit-proof isolating transformer

(inherently or non-inherently)
SMPS incorporating a
fail-safe safety isolating transformer
F
SMPS incorporating a
non-short-circuit-proof safety isolating
transformer
SMPS incorporating a
short-circuit-proof safety isolating transformer

(inherently or non-inherently)
SMPS incorporating a
or
F F
fail-safe auto-transformer
SMPS incorporating a
or
non-short-circuit proof auto-transformer

SMPS incorporating a
or
short-circuit proof auto-transformer (inherently or

non-inherently)
S
SMPS (Switch mode power supply unit)

9 Protection against electric shock
This clause of Part 1 is applicable.

– 14 – 61558-2-16  IEC:2009+A1:2013

10 Change of input voltage setting

This clause of Part 1 is applicable except as follows:

Addition:
10.101 A wide range (e.g. 100 V a.c. to 240 V a.c.) of supply voltage is allowed if the output
voltage does not exceed the rated output voltage and the no-load output voltage does not
exceed the limits of the output voltage deviation according to the type of transformer feeding

the appropriate output circuit.

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 SMPS 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:
– 1 000 V a.c. or 1 415 V ripple-free d.c. for SMPS incorporating separating transformers or
auto-transformers;
– 500 V a.c. or 708 V ripple-free d.c. for SMPS incorporating isolating transformers;
– 50 V a.c. or 120 V ripple-free d.c. for SMPS incorporating safety isolating transformers.
For independent transformers, this output voltage limitation applies even when output
windings, not intended for interconnection, are connected in series.
12.102 The difference between the no-load output voltage and the output voltage under
rated load shall not be excessive.
The difference between the no-load output voltage measured in this clause and the output

voltage under load measured during the test of Clause 11, expressed as a percentage of the
latter voltage, shall not exceed the values shown in Table 101.
U – U
no-load load
NOTE 1 The ratio is defined as follows:      × 100 %
U
load
where U is the no-load output voltage and U is the output voltage under load.

no-load load
61558-2-16  IEC:2009+A1:2013 – 15 –

Table 101 – Output voltages ratio

Type of transformer Ratio between no-load output voltage and output

Rated output voltage under load

%
VA
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
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 SMPS is connected to the rated supply
voltage at the rated supply frequency.
The difference shall not exceed the values shown in Table 101.
NOTE 2 The values of Table 101 are based on the values of Part 2-4 and are also applicable to SMPS according
to Part 2-1, 2-6, and 2-13.
12.103 Unless otherwise specified by the manufacturer, SMPS with high frequency output
rating shall be tested with 20 cm to 200 cm length of wire connected to the output terminals
under the most unfavourable conditions. Two twisted wires or cables rated 60227 IEC 53 may
be used. The cross sectional area of the conductors shall be determined according to the rated
output of the SMPS, and the current density shall not exceed 5 A/mm in normal use.
13 Short circuit voltage
This clause of Part 1 is applicable.
14 Heating
This clause of Part 1 is applicable, except as follows:
Addition:
14.101 For SMPS incorporating transformers with internal frequencies higher than 1 kHz,
thermocouples or equivalent means of measuring the temperatures may be used to determine
the temperature of the windings and the insulating materials.

The maximum values of Table 1 in Part 1 for winding temperatures shall be reduced by 10 °C
for the thermocouple measurements. The thermocouples shall be mounted only on accessible
surfaces of the incorporated transformers.
NOTE The thermo-couples should not be integrated in the windings.
15 Short-circuit and overload protection
This clause of Part 1 is applicable, except as follows:
Addition:
15.101 Electronic circuits shall be so designed and applied that a fault condition within the
SMPS will not cause electric shock, or fire hazard, and unintentional operation of the appliance
will not impair safety.
– 16 – 61558-2-16  IEC:2009+A1:2013

Compliance is checked by evaluation of the fault condition specified in Annex H of Part 1.

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.
18.3 Addition of a new box 5 for Table 8a:
Table 8a – Table of dielectric strength test voltages
Working voltage
Application of dielectric strength test voltage V
<50 150 300 600 1 000
5) Over functional insulation for windings intended
to be connected in series or parallel Working voltage + 500 V

Replacement of the text in footnote a of Table 8a:
a
For construction according to 26.2.4.1, test B the voltage is multiplied by the factor 1,25. For
the construction according to 26.2.4.2 the voltage is multiplied by the factor 1,35.
18.4 does not apply.
Addition:
The term transformer shall be replaced by SMPS where applicable.

18.101 SMPS shall fulfil the impulse test according to Table F.5 of IEC 60664-1 with 1,2/50
µs as follows:
After the test of 18.3, the SMPS shall be connected to the impulse test equipment. The impulse
test shall be carried out with 10 impulses of each polarity between the input and output
terminals of the SMPS. The interval between the impulses shall be at least 1 s if the impulses
are produced inside the SMPS.
During the test, there shall be no breakdown of the insulation between turns of a winding,
between input and output circuits, between adjacent input or output circuits, or between
the windings and any conductive core.
18.102 A partial discharge test according to IEC 60664-1, (test description see below) shall
be performed, if FIW wires are used and if the recurring peak working voltage U across the
t
insulation is greater than 750 V. The relevant recurring peak voltage is the maximum measured
voltage between the input and the output circuit of the SMPS, if the secondary side is earthed.
The measuring shall be done at 1,0 of the maximum rated input voltage.

61558-2-16  IEC:2009+A1:2013 – 17 –

A partial discharge test shall be done at the transformer for the SMPS with the measured

recurring peak voltage U , greater than 750 V peak.
t
U is the maximum peak working voltage;
t
t is 5 s;
t is 15 s.
Partial discharge shall be less than or equal to 10 pC at time t .
The test shall be done according to the following Figure 104.

For other applications higher values may be required (e.g. IEC 61800-5-1).

U
1,25 U
t
U
t
t
t t
1 1
IEC  1763/13
Figure 104 – Test voltages
19 Construction
This clause of Part 1 is applicable, except as follows:

19.1 Replacement:
19.1.1 SMPS incorporating auto-transformers
19.1.1.1 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:
19.1.1.2 Polarized 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.

– 18 – 61558-2-16  IEC:2009+A1:2013

19.1.1.3 Polarity detecting device (for no
...