IEC 61558-2-9:2024

Safety of transformers, reactors, power supply units and combinations thereof - Part 2-9: Particular requirements and tests for transformers and power supply units for class III handlamps

IEC 61558-2-9:2024 deals with the safety of transformers for class III handlamps and power supply units incorporating transformers for class III handlamps. Transformers incorporating electronic circuits are also covered by this document. This third edition cancels and replaces the second edition published in 2010. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous edition:
a) adjustment of structure and references in accordance with IEC 61558-1:2017;
b) addition of a new symbol for power supply unit with linearly regulated output voltage;
c) document is not only valid for transformers for tungsten filament handlamps.
It has the status of a group safety publication in accordance with IEC Guide 104.

Sécurité des transformateurs, bobines d'inductance, blocs d'alimentation et des combinaisons de ces éléments - Partie 2-9: Exigences particulières et essais pour les transformateurs et blocs d'alimentation pour lampes baladeuses de classe III

L'IEC 61558-2-9:2024 traite de la sécurité des transformateurs pour lampes baladeuses de classe III et des blocs d'alimentation qui incorporent des transformateurs pour lampes baladeuses de classe III. Les transformateurs qui incorporent des circuits électroniques sont également couverts par le présent document. Cette troisième édition annule et remplace la deuxième édition parue en 2010. Cette édition constitue une révision technique.
Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) la structure et les références ont été alignées sur l'IEC 61558-1:2017;
b) un nouveau symbole a été ajouté pour les blocs d'alimentation dont la régulation de la tension secondaire est linéaire;
c) le document ne s'applique pas seulement aux transformateurs pour lampes baladeuses à filament de tungstène.
Il a le statut d'une publication groupée de sécurité conformément au Guide IEC 104.

General Information

• Status: Published
• Publication Date: 06-Jun-2024
• ICS: 29.180 - Transformers. Reactors
• Technical Committee: TC 96 - Transformers and reactors
• Drafting Committee: MT 1 - TC 96/MT 1
• Current Stage: PPUB - Publication issued
• Start Date: 07-Jun-2024
• Completion Date: 21-Jun-2024

Relations

• Revises: IEC 61558-2-9:2010 - Safety of transformers, reactors, power supply units and combinations thereof - Part 2-9: Particular requirements and tests for transformers and power supply units for class III handlamps for tungsten filament lamps
• Effective Date: 05-Sep-2023

Overview

IEC 61558-2-9:2024 is the third edition of the IEC safety standard for transformers and power supply units for class III handlamps. It specifies particular requirements and tests for transformers (including those with electronic circuits) and power supplies that provide safety extra-low voltage (SELV) for handlamps. This edition updates the 2010 version, adjusts structure and references to align with IEC 61558-1:2017, adds a symbol for linearly regulated outputs, and expands applicability beyond tungsten filament lamps. IEC 61558-2-9:2024 has the status of a group safety publication (IEC Guide 104).

Key topics and technical requirements

The standard supplements IEC 61558-1 and focuses on practical safety and test criteria for class III handlamp transformers and linear power supplies. Major technical topics include:

• Scope and ratings: single-phase, air-cooled dry-type transformers (stationary or portable); rated supply voltage ≤ 1 000 V AC; rated output ≤ 10 kVA; internal operational frequencies ≤ 500 Hz (SMPS handled jointly with IEC 61558‑2‑16).
• Output limits for class III: no-load and rated outputs not exceeding 50 V AC or 120 V ripple‑free DC, with only small no-load/rated voltage differences.
• Protection against electric shock: SELV considerations and required insulation measures.
• Electrical tests: insulation resistance, dielectric strength, leakage current, short‑circuit and overload behavior.
• Thermal and mechanical requirements: heating limits, mechanical strength, resistance to heat/fire/tracking and corrosion.
• Marking, classification and symbols: including new symbol for linearly regulated output voltage.
• Construction and components: internal wiring, terminals, earthing provisions, creepage/clearance distances.
• Test methods and documentation: general notes on tests and required records to demonstrate compliance.

Practical applications

IEC 61558-2-9 is intended for use where safe low-voltage handlamps are required - for example, workshop and inspection handlamps that rely on SELV transformers or linear power supplies. The standard ensures that transformers and linear power supply units used with class III handlamps meet electrical, thermal and mechanical safety expectations.

Who should use this standard

• Transformer and power supply manufacturers (design and compliance)
• Product safety and compliance engineers
• Test laboratories and certification bodies
• OEMs integrating handlamp transformers into lighting products
• Regulatory and standards committees

Related standards

• IEC 61558-1:2017 (general requirements for safety of transformers and power supplies)
• IEC 61558-2-16 (particular requirements for switch mode power supplies - used together when applicable)
• IEC Guide 104 (group safety publication guidance)

Keywords: IEC 61558-2-9, transformer safety, class III handlamps, power supply units, SELV, handlamp transformers, IEC 2024.

Standards Content (Sample)

IEC 61558-2-9 ®
Edition 3.0 2024-06
REDLINE VERSION
INTERNATIONAL
STANDARD
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GROUP ENERGY EFFICIENCY PUBLICATION

Safety of transformers, reactors, power supply units and combinations thereof –
Part 2-9: Particular requirements and tests for transformers and power supply
units for class III handlamps for tungsten filament lamps

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IEC 61558-2-9 ®
Edition 3.0 2024-06
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
GROUP ENERGY EFFICIENCY PUBLICATION
Safety of transformers, reactors, power supply units and combinations thereof –
Part 2-9: Particular requirements and tests for transformers and power supply
units for class III handlamps for tungsten filament lamps
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.180 ISBN 978-2-8322-9128-3
– 2 – IEC 61558-2-9:2024 RLV  IEC 2024
CONTENTS
FOREWORD . 3
INTRODUCTION . 2
1 Scope . 7
2 Normative references . 8
3 Terms and definitions . 8
4 General requirements . 9
5 General notes on tests . 9
6 Ratings . 9
7 Classification . 9
8 Marking and other information . 10
9 Protection against electric shock . 11
10 Change of input voltage setting . 11
11 Output voltage and output current under load . 11
12 No-load output voltage . 11
13 Short-circuit voltage . 12
14 Heating . 12
15 Short-circuit and overload protection . 13
16 Mechanical strength . 13
17 Protection against harmful ingress of dust, solid objects and moisture . 13
18 Insulation resistance, dielectric strength and leakage current . 13
19 Construction . 13
20 Components . 15
21 Internal wiring . 15
22 Supply connection and other external flexible cables or cords . 15
23 Terminals for external conductors . 15
24 Provisions for protective earthing. 16
25 Screws and connections . 16
26 Creepage distances, clearances and distances through insulation . 16
27 Resistance to heat, fire and tracking . 16
28 Resistance to rusting . 16
Annexes . 17
Bibliography . 18

Table 101 – Symbols indicating the kind of transformer . 11
Table 101 102 – Ratio of output voltages for transformers for
class III tungsten filament handlamps Output voltage ratio . 12

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF TRANSFORMERS, REACTORS,
POWER SUPPLY UNITS AND COMBINATIONS THEREOF –

Part 2-9: Particular requirements and tests for transformers and
power supply units for class III handlamps for tungsten filament lamps

FOREWORD
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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9) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
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shall not be held responsible for identifying any or all such patent rights.
This redline version of the official IEC Standard allows the user to identify the changes
made to the previous edition IEC 61558-2-9:2010. A vertical bar appears in the margin
wherever a change has been made. Additions are in green text, deletions are in
strikethrough red text.
– 4 – IEC 61558-2-9:2024 RLV  IEC 2024
IEC 61558-2-9 has been prepared by IEC technical committee 96: Transformers, reactors,
power supply units and combinations thereof. It is an International Standard.
This third edition cancels and replaces the second edition published in 2010. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) adjustment of structure and references in accordance with IEC 61558-1:2017;
b) addition of a new symbol for power supply unit with linearly regulated output voltage;
c) document is not only valid for transformers for tungsten filament handlamps.
The text of this International Standard is based on the following documents:
Draft Report on voting
96/593/FDIS 96/597/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this document is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
It has the status of a group safety publication in accordance with IEC Guide 104.
This document is to be used in conjunction with IEC 61558-1:2017.
This document supplements or modifies the corresponding clauses in IEC 61558-1:2017, so as
to convert that publication into the IEC standard: Particular requirements and tests for
transformers and power supply units for class III handlamps.
A list of all parts in the IEC 61558 series published under the general title Safety of transformers,
reactors, power supply units and combinations thereof, can be found on the IEC website.
Future standards in this series will carry the new general title as cited above. Titles of existing
standards in this series will be updated at the time of the next edition.
Where this document states "addition", "modification" or "replacement", the relevant text of
IEC 61558-1:2017 is to be adopted accordingly.
In this document, the following print types are used:
– requirements proper: in roman type;
– test specifications: in italic type;
– explanatory matter: in smaller roman type.
In the text of this document, the words in bold are defined in Clause 3.

Subclauses, notes, figures and tables additional to those in IEC 61558-1:2017 are numbered
starting from 101; supplementary annexes are entitled AA, BB, etc.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
IMPORTANT – The "colour inside" logo on the cover page of this document indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.

– 6 – IEC 61558-2-9:2024 RLV  IEC 2024
INTRODUCTION
IEC TC 96 has a group safety function in accordance with IEC Guide 104 for transformers other
than those intended to supply distribution networks, in particular transformers and power supply
units intended to allow the application of protective measures against electric shock as defined
by TC 64, which is about Electrical installations and protection against electric shock, but in
certain cases including the limitation of voltage and horizontal safety function for SELV, in
accordance with IEC 60364-4-41.
The group safety function (GSF) is used because of responsibility for example for safety extra-
low voltage (SELV) in accordance with IEC 61140:2016, 5.2.6 and IEC 60364-4-41:2005,
414.3.1 or control circuits in accordance with IEC 60204-1:2016, 7.2.4.
The group safety function is used for each part of IEC 61558-2 because different standards of
the IEC 61558 series can be combined in one construction but in certain cases with no limitation
of rated output power.
For example an auto-transformer in accordance with IEC 61558-2-13 can be designed with a
separate SELV-circuit in accordance with the particular requirements for IEC 61558-2-6 relating
to the general requirements of IEC 61558-1.

SAFETY OF TRANSFORMERS, REACTORS,
POWER SUPPLY UNITS AND COMBINATIONS THEREOF –

Part 2-9: Particular requirements and tests for transformers and
power supply units for class III handlamps for tungsten filament lamps

1 Scope
Replacement:
This part of IEC 61558 deals with the safety of transformers for class III handlamps for
tungsten filament lamps and power supply units incorporating transformers for class III
handlamps for tungsten filament lamps. Transformers incorporating electronic circuits are
also covered by this document.
NOTE 1 Safety includes electrical, thermal and mechanical and chemical aspects.
Unless otherwise specified, from here onward, the term transformer covers transformers for
class III handlamps for tungsten filament lamps and power supply units incorporating
transformers for class III handlamps for tungsten filament lamps.
For power supply units (linear) this document is applicable. For switch mode power supply
units IEC 61558-2-16 is applicable together with this document. Where two requirements are
in conflict, the most severe takes precedence.
This document is applicable to stationary or portable, single-phase, air-cooled (natural or
forced) independent or associated dry-type transformers. The windings may can be
encapsulated or non-encapsulated.
This standard is applicable to transformers and power supply (linear) with internal
operational frequencies not exceeding 500 Hz.
This standard used in combination with Part 2-16 for switch mode power supply (SMPS) units
is also applicable to power supplies with internal operational frequencies higher than 500 Hz.
Where the two requirements are in conflict, the most severe take precedence.
The rated supply voltage does not exceed 1 000 V AC and the rated supply frequency and
the internal operational operating frequencies do not exceed 500 Hz.
Transformers for class III handlamps for tungsten filament lamps have the following
additional characteristics:
– the no-load output voltage and the rated output voltage do not exceed 50 V AC or 120 V
ripple-free DC;
– there is only a small difference between the no-load output voltage and the rated output
voltage.
The rated output does not exceed 10 kVA.
This document is not applicable to external circuits and their components intended to be
connected to the input terminals and output terminals of the transformers.
NOTE 2 Transformers covered by this document are only used in applications where double or reinforced
insulation between circuits is required by the installation rules or by the end product standard.

– 8 – IEC 61558-2-9:2024 RLV  IEC 2024
NOTE 2 Attention is drawn to the following, if necessary:
– for transformers intended to be used in vehicles, on board ships, and aircraft, additional
requirements (from other applicable standards, national rules, etc.) 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 can be applicable to transformers intended for use in special environments.
NOTE 3 Future technological development of transformers may can necessitate a need to
increase the upper limit of the frequencies. Until then this document may can be used as a
guidance document.
This group safety publication focusing on safety guidance is primarily intended to be used as a
product safety standard for the products mentioned in the scope but is also intended to be used
by technical committees in the preparation of publications for products similar to those
mentioned in the scope of this group safety publication, in accordance with the principles laid
down in IEC Guide 104 and lSO/lEC Guide 51.
One of the responsibilities of a technical committee is, wherever applicable, to make use of
basic safety publications and/or group safety publications in the preparation of its publications.
2 Normative references
IEC 61558-1:2017, Clause 2 is applicable, except as follows:
Addition:
IEC 60245-4:2011, Rubber insulated cables – Rated voltages up to and including 450/750 V –
Part 4: Cords and flexible cables
IEC 61558-1:20052017, Safety of power transformers, power supplies, reactors and similar
products Safety of transformers, reactors, power supply units and combinations thereof – Part 1:
General requirements and tests
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
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 61558-1:2017 apply,
except as follows:
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1 Transformers
Addition:
3.1.101
transformer for class III handlamps for tungsten filament lamps
associated safety isolating transformer intended to supply one or more class III handlamps
for tungsten filament lamps
3.1.102
power supply unit incorporating transformer for class III handlamps for tungsten
filament lamps
power supply unit where an associated safety isolating transformer is used intended to
supply one or more class III handlamps for tungsten filament lamps
4 General requirements
IEC 61558-1:2017, Clause 4 is applicable.
5 General notes on tests
IEC 61558-1:2017, Clause 5 is applicable.
6 Ratings
IEC 61558-1:2017, Clause 6 is applicable, except as follows:
Addition:
6.101 The rated output voltage shall not exceed 50 V AC or 120 V ripple-free DC.
For independent transformers, this output voltage limitation applies even when output
windings, not intended for interconnection, are connected in series.
6.102 The rated output shall not exceed 10 kVA.
6.103 The rated supply frequency and the internal operational operating frequencies
shall not exceed 500 Hz.
6.104 The rated supply voltage shall not exceed 1 000 V AC.
Compliance with the requirements of 6.101 to 6.104 is checked by inspection of the marking.
7 Classification
IEC 61558-1:2017, Clause 7 is applicable, except as follows:
7.2
Replacement:
7.2 According to short-circuit protection characteristic or protection against abnormal
conditions use:
– inherently short-circuit proof transformers;
– non-inherently short-circuit proof transformers.

– 10 – IEC 61558-2-9:2024 RLV  IEC 2024
7.3
Replacement:
7.3 According to their degree of protection provided ensured by the enclosure for
– portable transformers shall be code have a degree of protection of at least IP24 or higher.
7.5
Replacement:
7.5 According to their duty-timetype:
– continuous operation.
7.8
Replacement:
7.8 According to their transient overvoltage condition:
– overvoltage category II.
8 Marking and other information
IEC 61558-1:2017, Clause 8 is applicable, except as follows:
8.1 h)
Replacement of the content up to the first semi-colon by the following:
relevant graphical symbols shown in Table 101 that indicate the kind of transformer;
8.11
Addition:
The symbol for linear power supply units shall be used in conjunction with the symbol
indicating the kind of transformer.

Table 101 – Symbols indicating the kind of transformer
Symbol or graphical symbol Explanation or title Identification
Short-circuit proof transformer for class III
tungsten filament handlamps (inherently or IEC 60417-5953:2002-10
non-inherently)
Power supply unit, linear IEC 60417-6210:2013-10

Addition:
8.101
8.101 For transformers intended for connection to the supply by means of a cable or cord and
a plug, an instruction sheet or the equivalent shall be delivered with the transformer, drawing
the attention of the user to the fact that the output circuit(s) shall be protected in accordance
with national wiring rules.
9 Protection against electric shock
IEC 61558-1:2017, Clause 9 is applicable.
10 Change of input voltage setting
IEC 61558-1:2017, Clause 10 is applicable.
11 Output voltage and output current under load
IEC 61558-1:2017, Clause 11 is applicable, except as follows:
11.1
Replacement of the first paragraph by the following:
11.1 When the transformer is connected to the rated supply voltage at the rated supply
frequency and loaded with an impedance resulting in the rated output at the rated output
voltage, and for AC current, at the rated power factor, the output voltage under load shall
not differ from the rated output voltage by more than 5 %. For transformers with rectifiers,
the output voltage under load shall not differ from the rated output voltage by more than 10 %.
12 No-load output voltage
IEC 61558-1:2017, Clause 12 is applicable, except as follows:
Addition
– 12 – IEC 61558-2-9:2024 RLV  IEC 2024
The no-load output voltage is measured when the transformer is connected to the rated
supply voltage at the rated supply frequency at ambient temperature.
12.101 The no-load output voltage shall not exceed 50 V AC or 120 V ripple free DC.
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
load (as measured in 11.1) shall not be excessive.
The ratio between the no-load output voltage measured in Clause 12 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 102.
The difference is expressed as a percentage of the latter voltage calculated according to the
following formula:
The ratio is determined by Formula (1):
UU−
no-load load
×100 %
( )
(1)
U
load
where
U is the no-load output voltage, expressed in V;
no-load
U is the output voltage under load, expressed in V.
load
Table 101 102 – Ratio of output voltages for transformers for
class III tungsten filament handlamps Output voltage ratio
Rated output Ratio between no-load output voltage and output
voltage under load
VA %
– up to and including 63 7,5
– over 63 up to and including 630 5,0
– over 630 2,5
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 transformer is connected to the rated
supply voltage at the rated supply frequency.
The difference shall not exceed the values shown in Table 101.
13 Short-circuit voltage
IEC 61558-1:2017, Clause 13 is applicable.
14 Heating
IEC 61558-1:2017, Clause 14 is applicable.

15 Short-circuit and overload protection
IEC 61558-1:2017, Clause 15 is applicable.
16 Mechanical strength
IEC 61558-1:2017, Clause 16 is applicable.
17 Protection against harmful ingress of dust, solid objects and moisture
IEC 61558-1:2017, Clause 17 is applicable.
18 Insulation resistance, dielectric strength and leakage current
IEC 61558-1:2017, Clause 18 is applicable.
19 Construction
IEC 61558-1:2017, Clause 19 is applicable, except as follows:
19.1 General construction
Replacement:
19.1 The input and output circuits shall be electrically separated from each other, and the
construction shall be such that there is no possibility of any connection between these circuits,
either directly or indirectly via, through other metal conductive parts, except by deliberate
action.
Compliance is checked by inspection and measurements, taking Clause 18 and Clause 26 into
consideration.
19.1.1 The insulation between input and output winding(s) shall consist of double or
reinforced insulation (rated for the working voltage).
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 earthing shall
consist of at least basic insulation rated for the input voltage. The insulation between the
output windings and the body connected to earthing, shall consist of at least basic
insulation (rated for the output voltage);
– for class I transformers intended for connection to the mains supply by means of a plug,
the insulation between the input windings and the body shall consist of at least basic
insulation, and the insulation between the output windings and the body shall consist of
at least supplementary insulation (both basic and supplementary insulations rated for
the working voltage);
– for class II transformers, the insulation between the input windings and the body shall
consist of double or reinforced insulation (rated for the input voltage). The insulation
between the output windings and the body shall consist of double or reinforced
insulation (rated for the output voltage).
19.1.2 For transformers with intermediate conductive parts (e.g. the iron core) not
connected to the body and located between the input and output windings, the following
requirements are applicable.
– 14 – IEC 61558-2-9:2024 RLV  IEC 2024
19.1.2.1 For class I and class II transformers, the insulation between the input and output
windings via the intermediate conductive parts shall consist of double or reinforced
insulation (rated for the working voltage);
– for class II transformers, the insulation between the input windings and the body, and
between the output windings and the body via the intermediate conductive parts shall
consist of double or reinforced insulation (rated for the input and output voltage);
– for transformer other than independent (e.g. IP00), the insulation between the input and
output windings via the intermediate conductive parts shall consist of double or
reinforced insulation (rated for the working voltage);
19.1.2.2 As an alternative to 19.1.2.1 for class I transformer not intended to be connected
by means of a plug and for transformer different from independent (e.g. IP00), if the
construction assure that all laminated plates of the iron core are connected to earthing (e.g by
soldering / welding) and if the in data sheet or instruction sheet clearly state that the safety of
the transformer depends on the earthing connection and that is not possible to use in class II
equipment, than the following apply:
– the insulation between the input windings and the intermediate conductive part
connected to earth, and between the output windings and the intermediate conductive
part connected to earthing, shall consist of at least basic insulation (rated for the input
and output voltage);
19.1.2.3 In addition to 19.1.2.1 and 19.1.2.2 the insulation between the intermediate
conductive parts and the input windings, and between the intermediate conductive parts
and the output windings shall consist of at least basic insulation (rated for the input and
output voltage). An intermediate conductive part not separated from the input or output
windings or the body by at least basic insulation is considered to be connected to the relevant
part(s).
19.1.3 For class I transformers not intended for connection to the mains supply by means
of a plug, the insulation between the input and output windings may can consist of basic
insulation plus protective screening instead of double or reinforced insulation, provided
the following conditions are complied with:
– the insulation between the input winding and the protective screen shall comply with the
requirements for basic insulation (rated for the input voltage);
– the insulation between the output winding and the protective screen shall comply with the
requirements for basic insulation (rated for the output voltage);
– the protective screen shall, unless otherwise specified, consist of a metal foil or of a wire
wound screen extending at least the full width of the input winding and shall have no gaps
or holes;
– where the protective screen does not cover the entire width of the input winding,
additional adhesive tapes or equivalent insulation shall be used to ensure double
insulation in that area;
– if the protective screen is made of a foil, the turns shall be insulated from each other. In
case of only one turn, it shall have an isolated overlap of at least 3 mm;
– the wire of a wire-wound screen and the lead-out wire of the protective screen shall have
a cross-sectional area at least corresponding to the rated current of the overload protective
device to ensure that if a breakdown of insulation should occur, the overload protective
device will open the circuit before the lead-out wire is destroyed;
– the lead-out wire shall be soldered to the protective screen or secured in an equally reliable
manner.
NOTE For the purpose of this subclause, the term “windings” does not include internal circuits.
Examples of construction of windings are given in Annex M of IEC 61558-1:2017.

19.16 Portable transformers for use in irregular or harsh conditions
Replacement:
Portable transformers shall have a degree of protection code of at least IP24.
Addition:
19.101 There shall be no connection between output circuits and the protective earthing,
unless this is allowed for associated transformers by the relevant equipment standard.
19.102 There shall be no connection between output circuits and the body, unless this is
allowed for associated transformers by the relevant equipment standard.
Compliance is checked by inspection.
19.103 The input and output terminals for the connection of external wiring shall be so located
that the distance measured between the points of introduction of the conductors into these
terminals is not less than 25 mm. If a barrier is used to obtain this distance, the measurement
shall be made over and around the barrier which shall be of insulating material and permanently
fixed to the transformer.
Compliance is checked by inspection and by measurement disregarding intermediate
conductive parts.
19.104 Portable transformers having a rated output not exceeding 630 VA shall be class II.
20 Components
IEC 61558-1:2017, Clause 20 is applicable.
21 Internal wiring
IEC 61558-1:2017, Clause 21 is applicable.
22 Supply connection and other external flexible cables or cords
IEC 61558-1:2017, Clause 22 is applicable, except as follows:
22.5
Addition:
Power supply cords of transformers with a degree of protection code of other than IPX0 shall
not be lighter than at least ordinary polychloroprene sheathed cords (code designation 60245
IEC 57) according to IEC 60245-4:2011 – type 60245 IEC 57).
23 Terminals for external conductors
IEC 61558-1:2017, Clause 23 is applicable.

– 16 – IEC 61558-2-9:2024 RLV  IEC 2024
24 Provisions for protective earthing
IEC 61558-1:2017, Clause 24 is applicable.
25 Screws and connections
IEC 61558-1:2017, Clause 25 is applicable.
26 Creepage distances, clearances and distances through insulation
IEC 61558-1:2017, Clause 26 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
IEC 61558-1:2017, Clause 27 is applicable.
28 Resistance to rusting
IEC 61558-1:2017, Clause 28 is applicable.

Annexes
The annexes of IEC 61558-1:2017 are applicable.

– 18 – IEC 61558-2-9:2024 RLV  IEC 2024
Bibliography
The bibliography of IEC 61558-1:2017 is applicable, except as follows:
Addition:
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 60204-1:2016, Safety of machinery – Electrical equipment of machines – Part 1: General
requirements
IEC 61558 (all parts), Safety of transformers, reactors, power supply units and combinations
thereof
IEC 61558-2-6, Safety of transformers, reactors, power supply units and combinations thereof
– Part 2-6: Particular requirements and tests for safety isolating transformers and power supply
units incorporating safety isolating transformers for general applications
IEC 61558-2-13, 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
IEC Guide 104:2019, The preparation of safety publications and the use of basic safety
publications and group safety publications
ISO/IEC Guide 51:2014, Safety aspects – Guidelines for their inclusion in standards

____________
IEC 61558-2-9 ®
Edition 3.0 2024-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
GROUP ENERGY EFFICIENCY PUBLICATION
PUBLICATION GROUPÉE SUR L'EFFICACITÉ ÉNERGÉTIQUE
Safety of transformers, reactors, power supply units and combinations thereof –
Part 2-9: Particular requirements and tests for transformers and power supply
units for class III handlamps
Sécurité des transformateurs, bobines d'inductance, blocs d'alimentation et des
combinaisons de ces éléments –
Partie 2-9: Exigences particulières et essais pour les transformateurs et blocs
d'alimentation pour lampes baladeuses de classe III
– 2 – IEC 61558-2-9:2024  IEC 2024
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 7
3 Terms and definitions . 7
4 General requirements . 8
5 General notes on tests . 8
6 Ratings . 8
7 Classification . 8
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 . 14
21 Internal wiring . 14
22 Supply connection and other external flexible cables or cords . 14
23 Terminals for external conductors . 14
24 Provisions for protective earthing. 14
25 Screws and connections . 14
26 Creepage distances, clearances and distances through insulation . 14
27 Resistance to heat, fire and tracking . 15
28 Resistance to rusting . 15
Annexes . 16
Bibliography . 17

Table 101 – Symbols indicating the kind of transformer . 9
Table 102 – Output voltage ratio . 11

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF TRANSFORMERS, REACTORS,
POWER SUPPLY UNITS AND COMBINATIONS THEREOF –

Part 2-9: Particular requirements and tests for transformers and
power supply units for class III handlamps

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, IE
...

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Safety of transformers, reactors, power supply units and combinations thereof –
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IEC 61558-2-9 ®
Edition 3.0 2024-06
EXTENDED VERSION
INTERNATIONAL
STANDARD
colour
inside
This extended version of IEC 61558-2-9:2024 includes the content of the references made to
IEC 61558-1:2017
GROUP ENERGY EFFICIENCY PUBLICATION
Safety of transformers, reactors, power supply units and combinations thereof –
Part 2-9: Particular requirements and tests for transformers and power supply
units for class III handlamps
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.180 ISBN 978-2-8322-9129-0

– 2 – IEC 61558-2-9:2024 EXV  IEC 2024
CONTENTS
FOREWORD . 9
INTRODUCTION to IEC 61558-1:2017 . 12
INTRODUCTION to IEC 61558-2-9:2024 . 14
1 Scope . 15
2 Normative references . 16
3 Terms and definitions . 19
3.1 Transformers . 19
3.2 General terms . 23
3.3 Operations and protections . 24
3.4 Circuits and windings . 26
3.5 Ratings . 27
3.6 No-load values . 29
3.7 Insulation . 29
3.8 Touch current and protective earthing conductor current . 33
4 General requirements . 33
5 General notes on tests . 34
6 Ratings . 36
7 Classification . 36
8 Marking and other information . 37
9 Protection against electric shock . 44
9.1 General . 44
9.2 Protection against contact with hazardous-live-parts . 44
9.2.1 Determination of hazardous-live-parts . 44
9.2.2 Accessibility to hazardous-live-parts . 45
9.2.3 Accessibility to non hazardous-live-part . 48
9.3 Protection against hazardous electrical discharge . 48
10 Change of input voltage setting . 48
11 Output voltage and output current under load . 49
12 No-load output voltage . 49
13 Short-circuit voltage . 50
14 Heating . 51
14.1 General requirements . 51
14.1.1 Temperature-rise test . 51
14.1.2 Alternative temperature-rise test . 53
14.1.3 Determination of steady-state conditions . 55
14.2 Application of 14.1 or 14.3 according to the insulation system. 57
14.3 Accelerated ageing test for undeclared class of insulation system . 57
14.3.1 General . 57
14.3.2 Heat run . 58
14.3.3 Vibration . 58
14.3.4 Moisture treatment . 58
14.3.5 Measurements . 58
15 Short circuit and overload protection. 59
15.1 General requirements . 59
15.1.1 Short circuit and overload test method . 59

15.1.2 Alternative short circuit and overload test method . 61
15.2 Inherently short-circuit proof transformers . 61
15.3 Non-inherently short-circuit proof transformers. 61
15.4 Non-short-circuit proof transformers . 62
15.5 Fail-safe transformers . 62
16 Mechanical strength . 63
16.1 General . 63
16.2 Stationary transformers . 63
16.3 Portable transformers (except portable transformers with integral pins for
introduction in socket-outlet in the fixed wiring) . 64
16.4 Portable transformers provided with integral pins for introduction in socket-
outlets of the fixed wiring . 64
16.4.1 General requirements . 64
16.4.2 Portable transformers provided with integral pins according to EN
50075 (IEC plug type C) for introduction in socket-outlets of the fixed
wiring . 65
16.5 Additional requirements for transformers to be used in vehicles and railway
applications . 66
16.5.1 Transformers to be used in vehicles and railway applications . 66
16.5.2 Test requirements for the transportation of transformers . 67
17 Protection against harmful ingress of dust, solid objects and moisture . 68
17.1 Degrees of protection provided by enclosures (IP code) . 68
17.1.1 General requirements . 68
17.1.2 Tests on transformers with enclosure . 69
17.2 Humidity treatment . 71
18 Insulation resistance, dielectric strength and leakage current . 72
18.1 General . 72
18.2 Insulation resistance . 72
18.3 Dielectric strength test . 73
18.4 Insulation between and within windings . 75
18.5 Touch current and protective earthing conductor current . 75
18.5.1 General . 75
18.5.2 Touch current . 76
18.5.3 Protective earthing conductor current . 77
19 Construction . 77
19.1 General construction . 77
19.2 Flammability of materials . 79
19.3 Short-circuit characteristics of portable transformers . 79
19.4 Class II transformer contact prevention of accessible conductive parts . 79
19.5 Class II transformer insulation reassembling after service . 80
19.6 Loosening of wires, screws or similar parts . 80
19.7 Resistor or capacitor connection with accessible conductive parts . 80
19.8 Bridging of separated conductive parts by resistors or capacitors . 81
19.9 Insulating material separating input and output windings . 81
19.10 Accidental contact protection against hazardous-live-parts provided by
isolating coating . 82
19.11 Insulating material of handles, operating levers, knobs and similar parts. 83
19.12 Winding construction . 83
19.13 Fixing of handles, operating levers and similar parts . 87
19.14 Fixing of covers providing protection against electric shock . 87

– 4 – IEC 61558-2-9:2024 EXV  IEC 2024
19.15 Strain on fixed socket-outlets caused by pin-transformers connection . 87
19.16 Portable transformers for use in irregular or harsh conditions . 87
19.17 Drain hole of transformers protected against ingress of water . 87
19.18 Plug connected transformers protected against ingress of water . 87
19.19 Flexible cable or flexible cord connection for class I portable transformers . 88
19.20 SELV- and PELV-circuit separation of live parts . 88
19.21 Protection against contact for FELV-circuit. 88
19.22 Protective earthing regarding class II transformers . 89
19.23 Protective earthing regarding class III transformers . 89
20 Components . 89
21 Internal wiring . 94
22 Supply connection and other external flexible cables or cords . 95
23 Terminals for external conductors . 102
24 Provisions for protective earthing. 103
25 Screws and connections . 105
26 Creepage distances, clearances and distances through insulation . 107
26.1 General . 107
26.2 Creepage distances and clearances . 108
26.2.1 General . 108
26.2.2 Windings covered with adhesive tape . 108
26.2.3 Uncemented insulationing parts . 108
26.2.4 Cemented insulating parts . 108
26.2.5 Enclosed parts (e.g. by impregnation or potting) . 109
26.3 Distance through insulation . 110
27 Resistance to heat, fire and tracking . 121
27.1 General . 121
27.2 Resistance to heat . 121
27.2.1 General . 121
27.2.2 External accessible parts . 121
27.2.3 Internal parts . 122
27.3 Resistance to abnormal heat under fault conditions . 122
27.4 Resistance to fire . 123
27.4.1 General . 123
27.4.2 External accessible parts . 124
27.4.3 Internal parts . 124
27.5 Resistance to tracking . 125
28 Resistance to rusting . 125
Annex A (normative) Measurement of creepage distances and clearances. 126
Annex B (normative) Testing a series of transformers . 130
B.1 General . 130
B.2 Requirements . 130
B.3 Constructional inspection . 131
Annex C (void) . 132
Annex D (void) . 133
Annex E (normative) Glow-wire test . 134
E.1 General . 134
E.2 Severity . 134

E.3 Conditioning . 134
E.4 Test procedure . 134
Annex F (normative) Requirements for manually operated switches which are parts of
transformers assembly . 135
F.1 General . 135
F.2 Switches tested as a separate component . 135
F.3 Switches tested as part of the transformer . 135
Annex G (normative) Tracking test . 138
G.1 General . 138
G.2 Test specimen . 138
G.3 Test apparatus . 138
G.4 Procedure . 138
Annex H (normative) Electronic circuits . 139
H.1 General . 139
H.2 General notes on tests (addition to Clause 5). 139
H.3 Short circuit and overload protection (addition to Clause 15) . 139
H.4 Creepage distances, clearances and distances through insulation (addition
to Clause 26) . 141
Annex I (informative) Dimensions for rectangular cross-section connectors of
transformers, basic dimensions and coordination . 143
Annex J (normative) Measuring network for touch-currents . 145
Annex K (normative) Insulated winding wires . 146
K.1 General . 146
K.2 Type tests . 146
K.2.1 General . 146
K.2.2 Dielectric strength test . 146
K.2.3 Flexibility and adherence . 146
K.2.4 Heat shock . 147
K.2.5 Retention of dielectric strength after bending . 147
K.3 Testing during manufacturing . 148
K.3.1 General . 148
K.3.2 Routine test . 148
K.3.3 Sampling test . 148
Annex L (normative) Routine tests (production tests) . 149
L.1 General . 149
L.2 Protective earthing continuity test . 149
L.3 Checking of no-load output voltage . 149
L.4 Dielectric strength test . 149
L.5 Checking of protective devices mounting . 150
L.6 Visual inspection . 150
L.7 Repetition test after routine dielectric strength test . 150
Annex M (informative) Examples to be used as a guide for 19.1 . 151
M.1 General . 151
M.2 Coil-former . 151
M.2.1 Concentric type . 151
M.2.2 Side-by-side type . 152
M.3 Windings . 152
M.3.1 Without screen . 152

– 6 – IEC 61558-2-9:2024 EXV  IEC 2024
M.3.2 With screen . 153
Annex N (informative) Examples for checking points of dielectric strength test voltages . 154
Annex O (void) . 156
Annex P (informative) Examples for measurement points of creepage distances and
clearances . 157
Annex Q (informative) Explanation of IP numbers for degrees of protection . 160
Q.1 General . 160
Q.2 Degrees of protection against access to hazardous parts and against solid
foreign objects . 160
Q.3 Degrees of protection against ingress of water . 162
Annex R (normative) Explanations of the application of 6.1.2.2.1 of IEC 60664-1:2007 . 163
R.1 Impulse dielectric test . 163
R.2 Example. 163
Annex S (void) . 165
Annex T (void) . 166
Annex U (void) . 167
Annex V (informative) Symbols to be used for thermal cut-outs . 168
V.1 General . 168
V.2 Non-self-resetting thermal cut-out (see 3.3.4) . 168
V.3 Self-resetting thermal cut-out (see 3.3.3) . 168
Annex W (normative) Coated printed circuit boards . 169
W.1 Preamble . 169
W.2 General . 169
W.3 Cold . 169
W.4 Rapid change of temperature . 169
W.5 Additional tests . 169
Bibliography . 170
Index of defined terms . 172

Figure 1 – IEC 61558 principle . 13
Figure 2 – Mounting box for flush-type transformer . 35
Figure 3 – Test pin (see IEC 61032, test probe 13) . 46
Figure 4 – Standard test finger (see IEC 61032, test probe B) . 47
Figure 5 – Example of back-to-back method – Single phase . 55
Figure 6 – Example of back-to-back method – Three phase . 55
Figure 7 – Amplitude spectrum density for random testing . 67
Figure 8 – Normalised spectrum of shock . 68
Figure 9 – Test voltage sequence . 75
Figure 10 – Test configuration: single-phase equipment on star TN or TT system . 77
Figure 11 – Abrasion resistance test for insulating coated layers . 82
Figure 12 – Flexing test apparatus . 99
Figure 13 – Test arrangement for checking mechanical withstanding of insulating
materials in thin sheet layers . 113
Figure 14 – Ball-pressure apparatus . 121
Figure A.1 – Example 1. 126
Figure A.2 – Example 2. 127

Figure A.3 – Example 3. 127
Figure A.4 – Example 4. 127
Figure A.5 – Example 5. 128
Figure A.6 – Example 6. 128
Figure A.7 – Example 7. 129
Figure A.8 – Example 8. 129
Figure H.1 – Example of an electronic circuit with low-power points . 142
Figure J.1 – Measuring network for touch-current . 145
Figure M.1 – Examples for concentric type constructions . 151
Figure M.2 – Examples for side-by-side type constructions . 152
Figure M.3 – Examples for winding constructions without screen . 152
Figure M.4 – Examples for wrapped winding constructions . 153
Figure M.5 – Examples for winding constructions with screen . 153
Figure N.1 – Transformer of class I construction with metal enclosure . 154
Figure N.2 – Transformer of class II construction with metal enclosure . 155
Figure N.3 – Transformer of class II construction with enclosure of insulating material . 155
Figure P.1 – Transformer of class I construction . 157
Figure P.2 – Transformer of class I construction with earthed metal screen . 158
Figure P.3 – Transformer of class II construction with metal enclosure . 158
Figure P.4 – Transformer of class II construction with enclosure of insulating material . 159
Figure V.1 – Restored by manual operation . 168
Figure V.2 – Restored by disconnection of the supply . 168
Figure V.3 – Thermal link (see 3.3.5) . 168
Figure V.4 – Self-resetting thermal cut-out . 168

Table 1 – Symbols used on equipment or in instructions . 41
Table 101 – Symbols indicating the kind of transformer . 42
Table 102 – Output voltage ratio . 50
Table 2 – Values of maximum temperatures in normal use . 56
Table 3 – Explanation of the maximum winding temperatures required in Table 2 . 57
Table 4 – Test temperature and testing time (in days) per cycle . 58
Table 5 – Maximum values of temperatures under short-circuit or overload conditions . 60
Table 6 – Values of T and k for fuses . 61
Table 7 – Pull force on pins . 65
Table 8 – Conditions for vibration testing (random) . 66
Table 9 – Amplitude spectrum density ASD values for accelerated life testing . 66
Table 10 – Frequency values depending on the weight of the specimen . 67
Table 11 – Excitation values for vibration testing . 67
Table 12 – Solid-object-proof transformer test . 70
Table 13 – Values of insulation resistance . 73
Table 14 – Table of dielectric strength test voltages. 74
Table 15 – Limits for currents . 77
Table 16 – Nominal cross-sectional areas of external flexible cables or cords . 97

– 8 – IEC 61558-2-9:2024 EXV  IEC 2024
Table 17 – Pull and torque to be applied to external flexible cables or cords fixed to
stationary and portable transformers . 101
Table 18 – Torque to be applied to screws and connections . 106
Table 19 – Torque test on glands . 107
Table 20 – Clearances in mm . 114
Table 21 – Creepage distances in mm . 115
Table 22 – Distance through insulation in mm . 116
Table 23 – Creepage distances and clearance between terminals for external
connection . 117
Table 24 – Values of FIW wires with minimum overall diameter and minimum test
voltages according to the total enamel increase . 119
Table A.1 – Width of groove values depending on the pollution degree . 126
Table F.1 – Peak surge current of additional loads. 136
Table I.1 – Dimensions of rectangular copper connectors . 143
Table K.1 – Mandrel diameter . 147
Table K.2 – Oven temperature . 147
Table Q.1 – Degrees of protection against access to hazardous parts indicated by the
first characteristic numeral . 161
Table Q.2 – Degrees of protection against solid foreign objects indicated by the first
characteristic numeral . 161
Table Q.3 – Degrees of protection indicated by the second characteristic numeral . 162
Table R.1 – Impulse test voltage according to 6.1.2.2.1 of IEC 60664-1:2007 . 163

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF TRANSFORMERS, REACTORS,
POWER SUPPLY UNITS AND COMBINATIONS THEREOF –

Part 2-9: Particular requirements and tests for transformers and
power supply units for class III handlamps

FOREWORD
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– 10 – IEC 61558-2-9:2024 EXV  IEC 2024
IEC 61558-2-9 has been prepared by IEC technical committee 96: Transformers, reactors,
power supply units and combinations thereof. It is an International Standard.
This third edition cancels and replaces the second edition published in 2010. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) adjustment of structure and references in accordance with IEC 61558-1:2017;
b) addition of a new symbol for power supply unit with linearly regulated output voltage;
c) document is not only valid for transformers for tungsten filament handlamps.
The text of this International Standard is based on the following documents:
Draft Report on voting
96/593/FDIS 96/597/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this document is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement,
available at www.iec.ch/members_experts/refdocs. The main document types
...

IEC 61558-2-9 ®
Edition 3.0 2024-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
GROUP ENERGY EFFICIENCY PUBLICATION
PUBLICATION GROUPÉE SUR L'EFFICACITÉ ÉNERGÉTIQUE
Safety of transformers, reactors, power supply units and combinations thereof –
Part 2-9: Particular requirements and tests for transformers and power supply
units for class III handlamps
Sécurité des transformateurs, bobines d'inductance, blocs d'alimentation et des
combinaisons de ces éléments –
Partie 2-9: Exigences particulières et essais pour les transformateurs et blocs
d'alimentation pour lampes baladeuses de classe III
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IEC 61558-2-9 ®
Edition 3.0 2024-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
GROUP ENERGY EFFICIENCY PUBLICATION

PUBLICATION GROUPÉE SUR L'EFFICACITÉ ÉNERGÉTIQUE

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

Part 2-9: Particular requirements and tests for transformers and power supply

units for class III handlamps
Sécurité des transformateurs, bobines d'inductance, blocs d'alimentation et des

combinaisons de ces éléments –

Partie 2-9: Exigences particulières et essais pour les transformateurs et blocs

d'alimentation pour lampes baladeuses de classe III

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.180  ISBN 978-2-8322-8992-1

– 2 – IEC 61558-2-9:2024  IEC 2024
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 7
3 Terms and definitions . 7
4 General requirements . 8
5 General notes on tests . 8
6 Ratings . 8
7 Classification . 8
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 . 14
21 Internal wiring . 14
22 Supply connection and other external flexible cables or cords . 14
23 Terminals for external conductors . 14
24 Provisions for protective earthing. 14
25 Screws and connections . 14
26 Creepage distances, clearances and distances through insulation . 14
27 Resistance to heat, fire and tracking . 15
28 Resistance to rusting . 15
Annexes . 16
Bibliography . 17

Table 101 – Symbols indicating the kind of transformer . 9
Table 102 – Output voltage ratio . 11

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF TRANSFORMERS, REACTORS,
POWER SUPPLY UNITS AND COMBINATIONS THEREOF –

Part 2-9: Particular requirements and tests for transformers and
power supply units for class III handlamps

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and
in addition to other activities, IEC publishes International Standards, Technical Specifications, Technical Reports,
Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC Publication(s)”). Their
preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
may participate in this preparatory work. International, governmental and non-governmental organizations liaising
with the IEC also participate in this preparation. IEC collaborates closely with the International Organization for
Standardization (ISO) in accordance with conditions determined by agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence between
any IEC Publication and the corresponding national or regional publication shall be clearly indicated in the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). IEC takes no position concerning the evidence, validity or applicability of any claimed patent rights in
respect thereof. As of the date of publication of this document, IEC had not received notice of (a) patent(s), which
may be required to implement this document. However, implementers are cautioned that this may not represent
the latest information, which may be obtained from the patent database available at https://patents.iec.ch. IEC
shall not be held responsible for identifying any or all such patent rights.
IEC 61558-2-9 has been prepared by IEC technical committee 96: Transformers, reactors,
power supply units and combinations thereof. It is an International Standard.
This third edition cancels and replaces the second edition published in 2010. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) adjustment of structure and references in accordance with IEC 61558-1:2017;
b) addition of a new symbol for power supply unit with linearly regulated output voltage;
c) document is not only valid for transformers for tungsten filament handlamps.

– 4 – IEC 61558-2-9:2024  IEC 2024
The text of this International Standard is based on the following documents:
Draft Report on voting
96/593/FDIS 96/597/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this document is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/standardsdev/publications.
It has the status of a group safety publication in accordance with IEC Guide 104.
This document is to be used in conjunction with IEC 61558-1:2017.
This document supplements or modifies the corresponding clauses in IEC 61558-1:2017, so as
to convert that publication into the IEC standard: Particular requirements and tests for
transformers and power supply units for class III handlamps.
A list of all parts in the IEC 61558 series published under the general title Safety of transformers,
reactors, power supply units and combinations thereof, can be found on the IEC website.
Future standards in this series will carry the new general title as cited above. Titles of existing
standards in this series will be updated at the time of the next edition.
Where this document states "addition", "modification" or "replacement", the relevant text of
IEC 61558-1:2017 is to be adopted accordingly.
In this document, the following print types are used:
– requirements proper: in roman type;
– test specifications: in italic type;
– explanatory matter: in smaller roman type.
In the text of this document, the words in bold are defined in Clause 3.
Subclauses, notes, figures and tables additional to those in IEC 61558-1:2017 are numbered
starting from 101; supplementary annexes are entitled AA, BB, etc.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
INTRODUCTION
IEC TC 96 has a group safety function in accordance with IEC Guide 104 for transformers other
than those intended to supply distribution networks, in particular transformers and power supply
units intended to allow the application of protective measures against electric shock as defined
by TC 64, which is about Electrical installations and protection against electric shock, but in
certain cases including the limitation of voltage and horizontal safety function for SELV, in
accordance with IEC 60364-4-41.
The group safety function (GSF) is used because of responsibility for example for safety extra-
low voltage (SELV) in accordance with IEC 61140:2016, 5.2.6 and IEC 60364-4-41:2005,
414.3.1 or control circuits in accordance with IEC 60204-1:2016, 7.2.4.
The group safety function is used for each part of IEC 61558-2 because different standards of
the IEC 61558 series can be combined in one construction but in certain cases with no limitation
of rated output power.
For example an auto-transformer in accordance with IEC 61558-2-13 can be designed with a
separate SELV-circuit in accordance with the particular requirements for IEC 61558-2-6 relating
to the general requirements of IEC 61558-1.

– 6 – IEC 61558-2-9:2024  IEC 2024
SAFETY OF TRANSFORMERS, REACTORS,
POWER SUPPLY UNITS AND COMBINATIONS THEREOF –

Part 2-9: Particular requirements and tests for transformers and
power supply units for class III handlamps

1 Scope
Replacement:
This part of IEC 61558 deals with the safety of transformers for class III handlamps and
power supply units incorporating transformers for class III handlamps. Transformers
incorporating electronic circuits are also covered by this document.
NOTE 1 Safety includes electrical, thermal and mechanical aspects.
Unless otherwise specified, from here onward, the term transformer covers transformers for
class III handlamps and power supply units incorporating transformers for class III
handlamps.
For power supply units (linear) this document is applicable. For switch mode power supply
units IEC 61558-2-16 is applicable together with this document. Where two requirements are
in conflict, the most severe takes precedence.
This document is applicable to stationary or portable, single-phase, air-cooled (natural or
forced) independent or associated dry-type transformers. The windings can be encapsulated
or non-encapsulated.
The rated supply voltage does not exceed 1 000 V AC and the rated supply frequency and
the internal operating frequencies do not exceed 500 Hz.
Transformers have the following additional characteristics:
– the no-load output voltage and the rated output voltage do not exceed 50 V AC or 120 V
ripple-free DC;
– there is only a small difference between the no-load output voltage and the rated output
voltage.
The rated output does not exceed 10 kVA.
This document is not applicable to external circuits and their components intended to be
connected to the input terminals and output terminals of the transformers.
NOTE 2 Transformers covered by this document are only used in applications where double or reinforced
insulation between circuits is required by the installation rules or by the end product standard.
Attention is drawn to the following, if necessary:
– for transformers intended to be used in vehicles, on board ships, and aircraft, additional
requirements (from other applicable standards, national rules, etc.);
– measures to protect the enclosure and the components inside the enclosure against
external influences such as fungus, vermin, termites, solar-radiation, and icing;
– the different conditions for transportation, storage, and operation of the transformers;

– additional requirements in accordance with other appropriate standards and national rules
can be applicable to transformers intended for use in special environments.
Future technological development of transformers can necessitate a need to increase the
upper limit of the frequencies. Until then this document can be used as a guidance document.
This group safety publication focusing on safety guidance is primarily intended to be used as a
product safety standard for the products mentioned in the scope but is also intended to be used
by technical committees in the preparation of publications for products similar to those
mentioned in the scope of this group safety publication, in accordance with the principles laid
down in IEC Guide 104 and lSO/lEC Guide 51.
One of the responsibilities of a technical committee is, wherever applicable, to make use of
basic safety publications and/or group safety publications in the preparation of its publications.
2 Normative references
IEC 61558-1:2017, Clause 2 is applicable, except as follows:
Addition:
IEC 60245-4:2011, Rubber insulated cables – Rated voltages up to and including 450/750 V –
Part 4: Cords and flexible cables
IEC 61558-1:2017, Safety of transformers, reactors, power supply units and combinations
thereof – Part 1: General requirements and tests
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
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 61558-1:2017 apply,
except as follows:
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1 Transformers
Addition:
3.1.101
transformer for class III handlamps
associated safety isolating transformer intended to supply one or more class III handlamps
3.1.102
power supply unit incorporating transformer for class III handlamps
power supply unit where an associated safety isolating transformer is used intended to
supply one or more class III handlamps

– 8 – IEC 61558-2-9:2024  IEC 2024
4 General requirements
IEC 61558-1:2017, Clause 4 is applicable.
5 General notes on tests
IEC 61558-1:2017, Clause 5 is applicable.
6 Ratings
IEC 61558-1:2017, Clause 6 is applicable, except as follows:
Addition:
6.101 The rated output voltage shall not exceed 50 V AC or 120 V ripple-free DC.
For independent transformers, this output voltage limitation applies even when output
windings, not intended for interconnection, are connected in series.
6.102 The rated output shall not exceed 10 kVA.
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 1 000 V AC.
Compliance with the requirements of 6.101 to 6.104 is checked by inspection of the marking.
7 Classification
IEC 61558-1:2017, Clause 7 is applicable, except as follows:
7.2
Replacement:
7.2 According to short-circuit characteristic or protection against abnormal use:
– inherently short-circuit proof transformers;
– non-inherently short-circuit proof transformers.
7.3
Replacement:
7.3 According to their degree of protection ensured by the enclosure
– portable transformers shall have a degree of protection of at least IP24.

7.5
Replacement:
7.5 According to their duty-type:
– continuous operation.
7.8
Replacement:
7.8 According to their transient overvoltage condition:
– overvoltage category II.
8 Marking and other information
IEC 61558-1:2017, Clause 8 is applicable, except as follows:
8.1 h)
Replacement of the content up to the first semi-colon by the following:
relevant graphical symbols shown in Table 101 that indicate the kind of transformer;
8.11
Addition:
The symbol for linear power supply units shall be used in conjunction with the symbol
indicating the kind of transformer.
Table 101 – Symbols indicating the kind of transformer
Symbol or graphical symbol Explanation or title Identification
Short-circuit proof transformer for class III
IEC 60417-5953:2002-10
handlamps (inherently or non-inherently)

Power supply unit, linear IEC 60417-6210:2013-10

– 10 – IEC 61558-2-9:2024  IEC 2024
Addition:
8.101
For transformers intended for connection to the supply by means of a cable or cord and a plug,
an instruction sheet or the equivalent shall be delivered with the transformer, drawing the
attention of the user to the fact that the output circuit(s) shall be protected in accordance with
national wiring rules.
9 Protection against electric shock
IEC 61558-1:2017, Clause 9 is applicable.
10 Change of input voltage setting
IEC 61558-1:2017, Clause 10 is applicable.
11 Output voltage and output current under load
IEC 61558-1:2017, Clause 11 is applicable, except as follows:
11.1
Replacement of the first paragraph by the following:
11.1 When the transformer is connected to the rated supply voltage at the rated supply
frequency and loaded with an impedance resulting in the rated output at the rated output
voltage, and for AC current, at the rated power factor, the output voltage under load shall
not differ from the rated output voltage by more than 5 %. For transformers with rectifiers,
the output voltage under load shall not differ from the rated output voltage by more than 10 %.
12 No-load output voltage
IEC 61558-1:2017, Clause 12 is applicable, except as follows:
Addition
12.101 The no-load output voltage shall not exceed 50 V AC or 120 V ripple free DC.
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
load shall not be excessive.
The ratio between the no-load output voltage measured in Clause 12 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 102.

The ratio is determined by Formula (1):
UU−
no-load load
×100 %
( )
(1)
U
load
where
U is the no-load output voltage, expressed in V;
no-load
U is the output voltage under load, expressed in V.
load
Table 102 – Output voltage ratio
Rated output Ratio between no-load output voltage and output
voltage under load
VA %
– up to and including 63 7,5
– over 63 up to and including 630 5,0
– over 630 2,5
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 transformer is connected to the rated
supply voltage at the rated supply frequency.
13 Short-circuit voltage
IEC 61558-1:2017, Clause 13 is applicable.
14 Heating
IEC 61558-1:2017, Clause 14 is applicable.
15 Short-circuit and overload protection
IEC 61558-1:2017, Clause 15 is applicable.
16 Mechanical strength
IEC 61558-1:2017, Clause 16 is applicable.
17 Protection against harmful ingress of dust, solid objects and moisture
IEC 61558-1:2017, Clause 17 is applicable.
18 Insulation resistance, dielectric strength and leakage current
IEC 61558-1:2017, Clause 18 is applicable.

– 12 – IEC 61558-2-9:2024  IEC 2024
19 Construction
IEC 61558-1:2017, Clause 19 is applicable, except as follows:
19.1 General construction
Replacement:
19.1 The input and output circuits shall be electrically separated from each other, and the
construction shall be such that there is no possibility of any connection between these circuits,
either directly or indirectly, through other conductive parts, except by deliberate action.
Compliance is checked by inspection and measurements, taking Clause 18 and Clause 26 into
consideration.
19.1.1 The insulation between input and output winding(s) shall consist of double or
reinforced insulation (rated for the working voltage).
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 earthing shall
consist of at least basic insulation rated for the input voltage. The insulation between the
output windings and the body connected to earthing, shall consist of at least basic
insulation (rated for the output voltage);
– for class I transformers intended for connection to the mains supply by means of a plug,
the insulation between the input windings and the body shall consist of at least basic
insulation, and the insulation between the output windings and the body shall consist of
at least supplementary insulation (both basic and supplementary insulations rated for
the working voltage);
– for class II transformers, the insulation between the input windings and the body shall
consist of double or reinforced insulation (rated for the input voltage). The insulation
between the output windings and the body shall consist of double or reinforced
insulation (rated for the output voltage).
19.1.2 For transformers with intermediate conductive parts (e.g. the iron core) not
connected to the body and located between the input and output windings, the following
requirements are applicable.
19.1.2.1 For class I and class II transformers, the insulation between the input and output
windings via the intermediate conductive parts shall consist of double or reinforced
insulation (rated for the working voltage);
– for class II transformers, the insulation between the input windings and the body, and
between the output windings and the body via the intermediate conductive parts shall
consist of double or reinforced insulation (rated for the input and output voltage);
– for transformer other than independent (e.g. IP00), the insulation between the input and
output windings via the intermediate conductive parts shall consist of double or
reinforced insulation (rated for the working voltage);

19.1.2.2 As an alternative to 19.1.2.1 for class I transformer not intended to be connected
by means of a plug and for transformer different from independent (e.g. IP00), if the
construction assure that all laminated plates of the iron core are connected to earthing (e.g by
soldering / welding) and if the in data sheet or instruction sheet clearly state that the safety of
the transformer depends on the earthing connection and that is not possible to use in class II
equipment, than the following apply:
– the insulation between the input windings and the intermediate conductive part
connected to earth, and between the output windings and the intermediate conductive
part connected to earthing, shall consist of at least basic insulation (rated for the input
and output voltage);
19.1.2.3 In addition to 19.1.2.1 and 19.1.2.2 the insulation between the intermediate
conductive parts and the input windings, and between the intermediate conductive parts
and the output windings shall consist of at least basic insulation (rated for the input and
output voltage). An intermediate conductive part not separated from the input or output
windings or the body by at least basic insulation is considered to be connected to the relevant
part(s).
19.1.3 For class I transformers not intended for connection to the mains supply by means
of a plug, the insulation between the input and output windings can consist of basic
insulation plus protective screening instead of double or reinforced insulation, provided
the following conditions are complied with:
– the insulation between the input winding and the protective screen shall comply with the
requirements for basic insulation (rated for the input voltage);
– the insulation between the output winding and the protective screen shall comply with the
requirements for basic insulation (rated for the output voltage);
– the protective screen shall, unless otherwise specified, consist of a metal foil or of a wire
wound screen extending at least the full width of the input winding and shall have no gaps
or holes;
– where the protective screen does not cover the entire width of the input winding,
additional adhesive tapes or equivalent insulation shall be used to ensure double
insulation in that area;
– if the protective screen is made of a foil, the turns shall be insulated from each other. In
case of only one turn, it shall have an isolated overlap of at least 3 mm;
– the wire of a wire-wound screen and the lead-out wire of the protective screen shall have
a cross-sectional area at least corresponding to the rated current of the overload protective
device to ensure that if a breakdown of insulation should occur, the overload protective
device will open the circuit before the lead-out wire is destroyed;
– the lead-out wire shall be soldered to the protective screen or secured in an equally reliable
manner.
NOTE For the purpose of this subclause, the term “windings” does not include internal circuits.
Examples of construction of windings are given in Annex M of IEC 61558-1:2017.
19.16 Portable transformers for use in irregular or harsh conditions
Replacement:
Portable transformers shall have a degree of protection of at least IP24.
Addition:
19.101 There shall be no connection between output circuits and the protective earthing,
unless this is allowed for associated transformers by the relevant equipment standard.

– 14 – IEC 61558-2-9:2024  IEC 2024
19.102 There shall be no connection between output circuits and the body, unless this is
allowed for associated transformers by the relevant equipment standard.
Compliance is checked by inspection.
19.103 The input and output terminals for the connection of external wiring shall be so located
that the distance measured between the points of introduction of the conductors into these
terminals is not less than 25 mm. If a barrier is used to obtain this distance, the measurement
shall be made over and around the barrier which shall be of insulating material and permanently
fixed to the transformer.
Compliance is checked by inspection and by measurement disregarding intermediate
conductive parts.
19.104 Portable transformers having a rated output not exceeding 630 VA shall be class II.
20 Components
IEC 61558-1:2017, Clause 20 is applicable.
21 Internal wiring
IEC 61558-1:2017, Clause 21 is applicable.
22 Supply connection and other external flexible cables or cords
IEC 61558-1:2017, Clause 22 is applicable, except as follows:
22.5
Addition:
Power supply cords of transformers with a degree of protection of other than IPX0 shall be
at least ordinary polychloroprene sheathed cords according to IEC 60245-4:2011 – type 60245
IEC 57).
23 Terminals for external conductors
IEC 61558-1:2017, Clause 23 is applicable.
24 Provisions for protective earthing
IEC 61558-1:2017, Clause 24 is applicable.
25 Screws and connections
IEC 61558-1:2017, Clause 25 is applicable.
26 Creepage distances, clearances and distances through insulation
IEC 61558-1:2017, Clause 26 is applicable.

27 Resistance to heat, fire and tracking
IEC 61558-1:2017, Clause 27 is applicable.
28 Resistance to rusting
IEC 61558-1:2017, Clause 28 is applicable.

– 16 – IEC 61558-2-9:2024  IEC 2024
Annexes
The annexes of IEC 61558-1:2017 are applicable.

Bibliography
The bibliography of IEC 61558-1:2017 is applicable, except as follows:
Addition:
IEC 60204-1:2016, Safety of machinery – Electrical equipment of machines – Part 1: General
requirements
IEC 61558 (all parts), Safety of transformers, reactors, power supply units and combinations
thereof
IEC 61558-2-6, Safety of transformers, reactors, power supply units and combinations thereof
– Part 2-6: Particular requirements and tests for safety isolating transformers and power supply
units incorporating safety isolating transformers for general applications
IEC 61558-2-13, 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
IEC Guide 104:2019, The preparation of safety publications and the use of basic safety
publications and group safety publications
ISO/IEC Guide 51:2014, Safety aspects – Guidelines for their inclusion in standards

____________
– 18 – IEC 61558-2-9:2024  IEC 2024
SOMMAIRE
AVANT-PROPOS . 19
INTRODUCTION . 22
1 Domaine d'application . 23
2 Références normatives . 24
3 Termes et définitions . 24
4 Exigences générales . 25
5 Généralités sur les essais . 25
6 Caractéristiques assignées . 25
7 Classification . 26
8 Marquage et autres indications . 26
9 Protection contre les chocs électriques . 27
10 Changement de la tension primaire d'alimentation . 27
11 Tension secondaire et courant secondaire en charge . 27
12 Tension secondaire à vide . 28
13 Tension de court-circuit . 28
14 Échauffements . 28
15 Protection contre les courts-circuits et les surcharges . 29
16 Résistance mécanique. 29
17 Protection contre les effets nuisibles dus à la pénétration de poussière, d'objets
solides et de l'humidité . 29
18 Résistance d'isolement, rigidité diélectrique et courant de fuite . 29
19 Construction . 29
20 Composants . 31
21 Conducteurs internes . 31
22 Raccordement à l'alimentation et câbles souples externes . 32
23 Bornes pour conducteurs externes . 32
24 Dispositions en vue de la mise à la terre de protection . 32
25 Vis et connexions . 32
26 Lignes de fuite, distances d'isolement et distances à travers l'isolation . 32
27 Résistance à la chaleur, au feu et aux courants de cheminement . 32
28 Protection contre la rouille . 32
Annexes . 33
Bibliographie . 34

Tableau 101 – Symboles qui indiquent le type de transformateur . 27
Tableau 102 – Rapport de la tension secondaire . 28

COMMISSION ÉLECTROTECHNIQUE INTERNATIONALE
____________
SÉCURITÉ DES TRANSFORMATEURS, BOBINES D'INDUCTANCE,
BLOCS D'ALIMENTATION ET DES COMBINAISONS DE CES ÉLÉMENTS –

Partie 2-9: Exigences particulières et essais pour les transformateurs et
blocs d'alimentation pour lampes baladeuses de classe III

AVANT-PROPOS
1) La Commission Électrotechnique Internationale (IEC) est une organisation mondiale de normalisation composée
de l'ensemble des comités électrotechniques nationaux (Comités nationaux de l'IEC). L'IEC a pour objet
de favoriser la coopération internationale pour toutes les questions de normalisation dans les domaines
de l'électricité et de l'électronique. À cet effet, l'IEC – entre autres activités – publie des Normes internationales,
des Spécifications techniques, des Rapports techniques, des Spécifications accessibles au public (PAS) et
des Guides (ci-après dénommés "Publication(s) de l'IEC").
...