IEC 61558-2-8:2024
(Main)Safety of transformers, reactors, power supply units and combinations thereof - Part 2-8: Particular requirements and tests for transformers and power supply units for bells and chimes
Safety of transformers, reactors, power supply units and combinations thereof - Part 2-8: Particular requirements and tests for transformers and power supply units for bells and chimes
IEC 61558-2-8:2024 deals with the safety of bell and chime transformers and power supply units incorporating bell and chime transformers. 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) new symbol for power supply unit with linearly regulated output voltage.
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 2-8 : Exigences particulières et essais pour les transformateurs et blocs d'alimentation pour sonneries et carillons
L'IEC 61558-2-8:2024 traite de la sécurité des transformateurs pour sonneries et carillons et des blocs d’alimentation qui incorporent des transformateurs pour sonneries et carillons. 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.
Il a le statut de publication groupée de sécurité conformément au Guide 104 de l'IEC.
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IEC 61558-2-8 ®
Edition 3.0 2024-06
REDLINE VERSION
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GROUP ENERGY EFFICIENCY PUBLICATION
Safety of transformers, reactors, power supply units and combinations thereof –
Part 2-8: Particular requirements and tests for transformers and power supply
units for bells and chimes
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IEC 61558-2-8 ®
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 2-8: Particular requirements and tests for transformers and power supply
units for bells and chimes
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.180 ISBN 978-2-8322-9125-2
– 2 – IEC 61558-2-8:2024 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 . 10
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 . 14
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 . 16
21 Internal wiring . 16
22 Supply connection and other external flexible cables or cords . 16
23 Terminals for external conductors . 16
24 Provisions for protective earthing. 16
25 Screws and connections . 17
26 Creepage distances, clearances and distances through insulation . 17
27 Resistance to heat, fire and tracking . 17
28 Resistance to rusting . 17
Annexes . 18
Annex F (normative) Requirements for manually operated switches which are parts of
transformers assembly . 18
Bibliography . 19
Table 101 – Symbols indicating the kind of transformer . 11
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF TRANSFORMERS, REACTORS,
POWER SUPPLY UNITS AND COMBINATIONS THEREOF –
Part 2-8: Particular requirements and tests for transformers
and power supply units for bells and chimes
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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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) 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
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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 61558-2-8:2010. 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 61558-2-8:2024 RLV IEC 2024
IEC 61558-2-8 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) new symbol for power supply unit with linearly regulated output voltage.
The text of this document is based on the following documents:
Draft Report on voting
96/592/FDIS 96/598/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 bells and chimes.
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 61558-2-8:2024 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 2-8: Particular requirements and tests for transformers
and power supply units for bells and chimes
1 Scope
Replacement:
This part of IEC 61558 deals with the safety of bell and chime transformers and power supply
units incorporating bell and chime transformers. 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 bell and chime
transformers and power supply units incorporating bell and chime transformers.
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 take precedence.
This document is applicable to stationary, 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).
This standard used in combination with part 2-16 for switch mode power supply (SMPS) units
is also applicable to power supplies with internal operating frequencies higher than 500 Hz.
Where the two requirements are in conflict, the most severe takes precedence.
The rated supply voltage does not exceed 250 V AC and the rated supply frequency and
does the internal operating frequencies do not exceed 500 Hz. This standard is applicable to
transformers and linear power supply units with internal operating frequency not exceeding
500 Hz.
The rated output shall does not exceed 100 VA.
The no-load output voltage does not exceed 33 V AC or 46 V ripple-free DC, and the rated
output voltage does not exceed 24 V AC, or 33 V ripple-free DC.
Bell and chime transformers are generally intended to supply domestic sound signalling
equipment and other similar devices where the load is applied for short periods of time.
NOTE 2 A partial load may can be applied for illumination purposes.
This document is not applicable to external circuits and their components intended to be
connected to the input terminals and output terminals of the transformers.
NOTE 3 Transformers covered by this document are 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 61558-2-8:2024 RLV IEC 2024
NOTE 4 Normally the transformers are intended to be used with equipment to provide voltages different from the
supply voltage for the functional requirements of the equipment. The protection against electric shock may can be
provided (or completed) by other features of the equipment, such as the body. Parts of output circuits may can be
connected to the input circuits or to protective earthing.
This document is applicable to transformers associated with specific equipment, to the extent
decided upon by the relevant IEC technical committees.
NOTE 4 Attention is drawn to the following, if 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,
such as tropical environment.
NOTE 5 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
This clause of IEC 61558-1:2017 is applicable except as follows:
Addition:
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
bell and chime transformer
single-phase safety isolating transformer specifically intended to supply household sound
signalling equipment and other similar devices
4 General requirements
This clause of IEC 61558-1:2017 is applicable.
5 General notes on tests
This clause of IEC 61558-1:2017 is applicable.
6 Ratings
Replacement :
This clause of IEC 61558-1:2017 is applicable except as follows:
Addition:
6.101 The rated output voltage shall not exceed 24 V AC or 33 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 100 VA.
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 250 V AC.
Compliance with the requirements of 6.101 to 6.104 is checked by inspection of the marking.
7 Classification
This clause of IEC 61558-1:2017 is applicable except as follows:
7.2
Replacement:
7.2 Transformers are classified according to the short-circuit protection characteristic or
protection against abnormal use:
– inherently short-circuit proof transformers;
– non-inherently short-circuit proof transformers;
– fail-safe transformers.
– 10 – IEC 61558-2-8:2024 RLV IEC 2024
7.4
Replacement:
7.4 Transformers are classified according to their mobility:
– fixed transformers.
7.5
Replacement:
7.5 Transformers are classified according to their duty-type:
– short-time duty cycle;
– intermittent duty cycle.
NOTE 1 A partial load for illumination may can be applied continuously.
7.8
Replacement:
7.8 Transformers are classified according to their transient overvoltage condition:
– overvoltage category II
Addition:
7.101 Transformers are classified according to the method of mounting:
– mounting in a distribution assembly;
– mounting in sound signalling devices (bells, chimes, buzzers, etc.);
– mounting on an outlet box or cabinet;
– flush mounted;
– surface mounted.
8 Marking and other information
This clause of IEC 61558-1:2017 is applicable except as follows:
8.1 h) Replacement:
The transformers shall be marked with one of the graphical symbols shown in 8.11;
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:
Symbol or graphical symbol Explanation or title Identification
Fail-safe bell and chime transformer Based on
Symbol
IEC 60417-
F
5013 (2009-
05)
Short-circuit proof bell and chime
transformer (inherently or non-inherently) IEC 60417-
5013 (2009-
05)
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
Fail-safe bell and chime transformer IEC 60417-5013:2002-10
modified
Short-circuit-proof bell and chime transformer IEC 60417-5013:2002-10
(inherently or non-inherently)
Power supply unit, linear IEC 60417-6210:2013-10
9 Protection against electric shock
This clause of IEC 61558-1:2017 is applicable except as follows:
Addition:
9.101 Protection against accidental contact with windings and hazardous live parts of the
input circuit shall be ensured while connecting conductors to the output terminals.
– 12 – IEC 61558-2-8:2024 RLV IEC 2024
Compliance is checked by inspection and by the application of the standard test finger shown
in Figure 2 4. It shall not be possible to touch windings or hazardous live parts of the input
circuit with the test finger.
10 Change of input voltage setting
This clause of IEC 61558-1:2017 is applicable.
11 Output voltage and output current under load
This clause of IEC 61558-1:2017 is applicable except as follows:
11.1
Replacement:
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 shall not differ from
the rated value by more than:
a) 15 % for the output voltage of inherently short-circuit proof transformers with one rated
output voltage;
b) 15 % for the highest output voltage of inherently short-circuit proof transformers with
more than one rated output voltage;
c) 20 % for the other output voltages of inherently short-circuit proof transformers with
more than one rated output voltage;
d) 15 % for the output voltages of other transformers.
Compliance is checked by measuring the output voltage 2 min after 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 the rated power
factor.
For transformers with more than one rated supply voltage, the requirement is applicable for
each of the rated supply voltages.
For transformers with multiple output windings, the loads are applied to every multiple section
simultaneously, unless otherwise declared.
12 No-load output voltage
This clause of IEC 61558-1:2017 is applicable except as follows:
Addition:
The no-load output voltage is measured when the transformer is connected to the rated
supply voltage at the rated supply frequency at ambient temperature.
12.101 The no-load output voltage shall not exceed 33 V AC or 46 V ripple free DC.
For independent transformers, this output voltage limitation applies even when independent
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 difference 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 100 %.
NOTE 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
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
This clause of IEC 61558-1:2017 is applicable.
14 Heating
This clause of IEC 61558-1:2017 is applicable except as follows:
14.1.1 Temperature-rise test
Replacement of the second third paragraph:
Temperatures are determined under the following conditions.
Replacement of the tenth eleventh paragraph:
Transformers are supplied at rated supply voltage and loaded with an impedance Z producing
rated output at the rated output voltage and, for AC current, at the rated power factor. The
value of output current is measured after 1 min. Then the supply voltage is increased by 10 %
and the output impedance is adjusted so that the new impedance Z’ gives the same output
current than the value measured before. Transformers are submitted to 20 cycles of 1 min
operation with the impedance Z’ and 5 min operation with 5 times the impedance Z’.
Temperature rises are measured during the last cycle.
14.1.3 Determination of steady-state conditions
Addition of the following footnote to table “f“ to "External enclosures" in Table 1 “g“ in Table 2
to "External enclosures":
fg The external enclosure of a transformer only includes the parts accessible to the standard test finger when
mounted in accordance with 14.1.1.
Addition of the following footnote to table “g“ to "supports" in Table 1 “h“ in Table 2 to "Supports":
– 14 – IEC 61558-2-8:2024 RLV IEC 2024
gh Support includes any area of the black painted plywood support, but excludes any metal parts of the mounting
system (rails, outlet boxes, etc.).
15 Short-circuit and overload protection
This clause of IEC 61558-1:2017 is applicable except as follows:
Addition:
15.101 The maximum short-circuit output current shall not exceed 10 A, measured 5 s after
applying the short-circuit, the transformer being supplied with 1,1 times the rated supply
voltage.
16 Mechanical strength
This clause of IEC 61558-1:2017 is applicable except as follows:
16.2 Stationary transformers
Replacement:
The impact hammer shall have an energy of (0,2 ± 0,05) J.
17 Protection against harmful ingress of dust, solid objects and moisture
This clause of IEC 61558-1:2017 is applicable.
18 Insulation resistance, dielectric strength and leakage current
This clause of IEC 61558-1:2017 is applicable.
19 Construction
This clause of IEC 61558-1:2017 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 insulation
between the input windings and any intermediate conductive part shall consist of at least
basic insulation, and the insulation between the output windings and any intermediate
conductive part shall consist of at least supplementary insulation (both basic and
supplementary insulations rated for the working voltage).
NOTE 1 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).
NOTE 2 Basic insulation and supplementary insulation are interchangeable.
In addition, the following applies:
– for class I transformers, the insulation between the input and output windings via the
intermediate conductive parts (even if they are connected to earthing) 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 via
the intermediate conductive parts (if any) shall consist of double or reinforced
insulation (rated for the input voltage), and the insulation between the body and the
output windings via the intermediate conductive parts (if any) and the body via the
intermediate conductive parts shall consist of double or reinforced insulation (rated
for the input and output voltage);
– for transformers different from independent (IP00), the insulation between the input
and output windings via the intermediate conductive parts shall consist of double or
reinforced insulation (rated for the working voltage).
NOTE 3 In 19.1.2 the possibility to consider the intermediate metal part connected to earthing and consequently to
require basic insulation in both circuits (primary and secondary) is not allowed for the following reason:
– the intermediate metal part is normally the iron core made by laminated plates insulated to each other by oxide.
It is not assured that all foils are correctly connected to the earthing.
– for transformers different from independent, it is not assured that in the final applications the iron core will be
connected to earthing.
Addition:
19.101 There shall be no connections between the output circuit and the protective earthing,
unless allowed by the relevant equipment standard for associated transformers.
19.102 There shall be no connections between the output circuit and the body, unless this
is allowed by the relevant equipment standard for associated transformers.
Compliance is checked by inspection.
19.103 These 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
– 16 – IEC 61558-2-8:2024 RLV IEC 2024
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.
20 Components
This clause of IEC 61558-1:2017 is applicable. except as follows:
20.4
Modification:
20.4 If the transformer incorporates a switch intended to disconnect the input winding from
the supply, this switch may can be of single-pole micro-gap construction and may can
disconnect either pole.
21 Internal wiring
This clause of IEC 61558-1:2017 is applicable.
22 Supply connection and other external flexible cables or cords
This clause of IEC 61558-1:2017 is applicable except as follows:
Modification:
22.3
Replacement of the first paragraph as follows:
22.3 Flush-type transformers may can be designed so that connection of the external
conductors to the terminals has to be are made before the transformer is fitted into a flush
mounting box.
22.5
Replacement:
22.5 Power supply cords of transformers shall not be lighter than light at least ordinary
polyvinyl chloride sheathed flexible cords (code designation 60227 IEC 53) according to
IEC 60227-5:2011 – type 60227 IEC 53 or ordinary tough rubber sheathed flexible cords (code
designation 60245 IEC 53) according to IEC 60245-4:2011 – type 60245 IEC 53.
23 Terminals for external conductors
This clause of IEC 61558-1:2017 is applicable.
24 Provisions for protective earthing
This clause of IEC 61558-1:2017 is applicable.
25 Screws and connections
This clause of IEC 61558-1:2017 is applicable except as follows:
25.3
Addition:
This requirement is not applicable to electrical connections other than protective earthing
connections on the output circuits of the transformers with a rated output not exceeding
12 VA.
26 Creepage distances, clearances and distances through insulation
This clause of IEC 61558-1:2017 is applicable.
27 Resistance to heat, fire and tracking
This clause of IEC 61558-1:2017 is applicable.
28 Resistance to rusting
This clause of IEC 61558-1:2017 is applicable.
– 18 – IEC 61558-2-8:2024 RLV IEC 2024
Annexes
The annexes of IEC 61558-1:2017 are applicable except as follows:
Annex F
(normative)
Requirements for manually operated switches
which are parts of transformers assembly
This annex of IEC 61558-1:2017 is applicable except as follows:
F.2 Switches tested as a separate component
Addition:
Add a third dash after the first paragraph of F.2:
– subclause 7.1.4.4: the number of operating cycles shall be 1 000.
Addition of a third bullet point after the first paragraph of Clause F.2:
• 7.4.7: the number of operating cycles shall be 1 000.
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 61058-1:2016, Switches for appliances – Part 1: General requirements
IEC 61558 (all parts), Safety of transformers, reactors, power supply units and combinations
thereof
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 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
ISO/IEC GUIDE 51:2014, Safety aspects – Guidelines for their inclusion in standards
____________
IEC 61558-2-8 ®
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 2-8: Particular requirements and tests for transformers and power supply
units for bells and chimes
Sécurité des transformateurs, bobines d'inductance, blocs d'alimentation et des
combinaisons de ces éléments –
Partie 2-8 : Exigences particulières et essais pour les transformateurs et blocs
d'alimentation pour sonneries et carillons
– 2 – IEC 61558-2-8:2024 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 . 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. 15
25 Screws and connections .
...
IEC 61558-2-8 ®
Edition 3.0 2024-06
EXTENDED VERSION
INTERNATIONAL
STANDARD
colour
inside
This extended version of IEC 61558-2-8:2024 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 2-8: Particular requirements and tests for transformers and power supply
units for bells and chimes
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
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IEC 61558-2-8 ®
Edition 3.0 2024-06
EXTENDED VERSION
INTERNATIONAL
STANDARD
colour
inside
This extended version of IEC 61558-2-8:2024 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 2-8: Particular requirements and tests for transformers and power supply
units for bells and chimes
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.180 ISBN 978-2-8322-9127-6
– 2 – IEC 61558-2-8:2024 EXV IEC 2024
CONTENTS
FOREWORD . 9
INTRODUCTION to IEC 61558-1:2017 . 12
INTRODUCTION to IEC 61558-2-8:2024 . 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 . 33
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 . 49
11 Output voltage and output current under load . 49
12 No-load output voltage . 50
13 Short-circuit voltage . 50
14 Heating . 50
14.1 General requirements . 50
14.1.1 Temperature-rise test . 50
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 . 58
14.3.1 General . 58
14.3.2 Heat run . 58
14.3.3 Vibration . 58
14.3.4 Moisture treatment . 59
14.3.5 Measurements . 59
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 . 72
18.4 Insulation between and within windings . 74
18.5 Touch current and protective earthing conductor current . 74
18.5.1 General . 74
18.5.2 Touch current . 75
18.5.3 Protective earthing conductor current . 76
19 Construction . 76
19.1 General construction . 76
19.2 Flammability of materials . 78
19.3 Short-circuit characteristics of portable transformers . 78
19.4 Class II transformer contact prevention of accessible conductive parts . 78
19.5 Class II transformer insulation reassembling after service . 78
19.6 Loosening of wires, screws or similar parts . 78
19.7 Resistor or capacitor connection with accessible conductive parts . 79
19.8 Bridging of separated conductive parts by resistors or capacitors . 79
19.9 Insulating material separating input and output windings . 80
19.10 Accidental contact protection against hazardous-live-parts provided by
isolating coating . 80
19.11 Insulating material of handles, operating levers, knobs and similar parts. 81
19.12 Winding construction . 81
19.13 Fixing of handles, operating levers and similar parts . 85
19.14 Fixing of covers providing protection against electric shock . 85
– 4 – IEC 61558-2-8:2024 EXV IEC 2024
19.15 Strain on fixed socket-outlets caused by pin-transformers connection . 86
19.16 Portable transformers for use in irregular or harsh conditions . 86
19.17 Drain hole of transformers protected against ingress of water . 86
19.18 Plug connected transformers protected against ingress of water . 86
19.19 Flexible cable or flexible cord connection for class I portable transformers . 86
19.20 SELV- and PELV-circuit separation of live parts . 86
19.21 Protection against contact for FELV-circuit. 87
19.22 Protective earthing regarding class II transformers . 87
19.23 Protective earthing regarding class III transformers . 87
20 Components . 88
21 Internal wiring . 93
22 Supply connection and other external flexible cables or cords . 94
23 Terminals for external conductors . 100
24 Provisions for protective earthing. 102
25 Screws and connections . 103
26 Creepage distances, clearances and distances through insulation . 106
26.1 General . 106
26.2 Creepage distances and clearances . 106
26.2.1 General . 106
26.2.2 Windings covered with adhesive tape . 106
26.2.3 Uncemented insulationing parts . 107
26.2.4 Cemented insulating parts . 107
26.2.5 Enclosed parts (e.g. by impregnation or potting) . 107
26.3 Distance through insulation . 109
27 Resistance to heat, fire and tracking . 119
27.1 General . 119
27.2 Resistance to heat . 119
27.2.1 General . 119
27.2.2 External accessible parts . 119
27.2.3 Internal parts . 120
27.3 Resistance to abnormal heat under fault conditions . 120
27.4 Resistance to fire . 121
27.4.1 General . 121
27.4.2 External accessible parts . 122
27.4.3 Internal parts . 122
27.5 Resistance to tracking . 123
28 Resistance to rusting . 123
Annex A (normative) Measurement of creepage distances and clearances. 124
Annex B (normative) Testing a series of transformers . 128
B.1 General . 128
B.2 Requirements . 128
B.3 Constructional inspection . 129
Annex C (void) . 130
Annex D (void) . 131
Annex E (normative) Glow-wire test . 132
E.1 General . 132
E.2 Severity . 132
E.3 Conditioning . 132
E.4 Test procedure . 132
Annex F (normative) Requirements for manually operated switches which are parts of
transformers assembly . 133
F.1 General . 133
F.2 Switches tested as a separate component . 133
F.3 Switches tested as part of the transformer . 133
Annex G (normative) Tracking test . 136
G.1 General . 136
G.2 Test specimen . 136
G.3 Test apparatus . 136
G.4 Procedure . 136
Annex H (normative) Electronic circuits . 137
H.1 General . 137
H.2 General notes on tests (addition to Clause 5). 137
H.3 Short circuit and overload protection (addition to Clause 15) . 137
H.4 Creepage distances, clearances and distances through insulation (addition
to Clause 26) . 139
Annex I (informative) Dimensions for rectangular cross-section connectors of
transformers, basic dimensions and coordination . 141
Annex J (normative) Measuring network for touch-currents . 143
Annex K (normative) Insulated winding wires . 144
K.1 General . 144
K.2 Type tests . 144
K.2.1 General . 144
K.2.2 Dielectric strength test . 144
K.2.3 Flexibility and adherence . 144
K.2.4 Heat shock . 145
K.2.5 Retention of dielectric strength after bending . 145
K.3 Testing during manufacturing . 146
K.3.1 General . 146
K.3.2 Routine test . 146
K.3.3 Sampling test . 146
Annex L (normative) Routine tests (production tests) . 147
L.1 General . 147
L.2 Protective earthing continuity test . 147
L.3 Checking of no-load output voltage . 147
L.4 Dielectric strength test . 147
L.5 Checking of protective devices mounting . 148
L.6 Visual inspection . 148
L.7 Repetition test after routine dielectric strength test . 148
Annex M (informative) Examples to be used as a guide for 19.1 . 149
M.1 General . 149
M.2 Coil-former . 149
M.2.1 Concentric type . 149
M.2.2 Side-by-side type . 150
M.3 Windings . 150
M.3.1 Without screen . 150
– 6 – IEC 61558-2-8:2024 EXV IEC 2024
M.3.2 With screen . 151
Annex N (informative) Examples for checking points of dielectric strength test voltages . 152
Annex O (void) . 154
Annex P (informative) Examples for measurement points of creepage distances and
clearances . 155
Annex Q (informative) Explanation of IP numbers for degrees of protection . 158
Q.1 General . 158
Q.2 Degrees of protection against access to hazardous parts and against solid
foreign objects . 158
Q.3 Degrees of protection against ingress of water . 160
Annex R (normative) Explanations of the application of 6.1.2.2.1 of IEC 60664-1:2007 . 161
R.1 Impulse dielectric test . 161
R.2 Example. 161
Annex S (void) . 163
Annex T (void) . 164
Annex U (void) . 165
Annex V (informative) Symbols to be used for thermal cut-outs . 166
V.1 General . 166
V.2 Non-self-resetting thermal cut-out (see 3.3.4) . 166
V.3 Self-resetting thermal cut-out (see 3.3.3) . 166
Annex W (normative) Coated printed circuit boards . 167
W.1 Preamble . 167
W.2 General . 167
W.3 Cold . 167
W.4 Rapid change of temperature . 167
W.5 Additional tests . 167
Bibliography . 168
Index of defined terms . 170
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 . 54
Figure 6 – Example of back-to-back method – Three phase . 55
Figure 7 – Amplitude spectrum density for random testing . 66
Figure 8 – Normalised spectrum of shock . 67
Figure 9 – Test voltage sequence . 74
Figure 10 – Test configuration: single-phase equipment on star TN or TT system . 76
Figure 11 – Abrasion resistance test for insulating coated layers . 81
Figure 12 – Flexing test apparatus . 97
Figure 13 – Test arrangement for checking mechanical withstanding of insulating
materials in thin sheet layers . 111
Figure 14 – Ball-pressure apparatus . 119
Figure A.1 – Example 1. 124
Figure A.2 – Example 2. 125
Figure A.3 – Example 3. 125
Figure A.4 – Example 4. 125
Figure A.5 – Example 5. 126
Figure A.6 – Example 6. 126
Figure A.7 – Example 7. 127
Figure A.8 – Example 8. 127
Figure H.1 – Example of an electronic circuit with low-power points . 140
Figure J.1 – Measuring network for touch-current . 143
Figure M.1 – Examples for concentric type constructions . 149
Figure M.2 – Examples for side-by-side type constructions . 150
Figure M.3 – Examples for winding constructions without screen . 150
Figure M.4 – Examples for wrapped winding constructions . 151
Figure M.5 – Examples for winding constructions with screen . 151
Figure N.1 – Transformer of class I construction with metal enclosure . 152
Figure N.2 – Transformer of class II construction with metal enclosure . 153
Figure N.3 – Transformer of class II construction with enclosure of insulating material . 153
Figure P.1 – Transformer of class I construction . 155
Figure P.2 – Transformer of class I construction with earthed metal screen . 156
Figure P.3 – Transformer of class II construction with metal enclosure . 156
Figure P.4 – Transformer of class II construction with enclosure of insulating material . 157
Figure V.1 – Restored by manual operation . 166
Figure V.2 – Restored by disconnection of the supply . 166
Figure V.3 – Thermal link (see 3.3.5) . 166
Figure V.4 – Self-resetting thermal cut-out . 166
Table 1 – Symbols used on equipment or in instructions . 41
Table 101 – Symbols indicating the kind of transformer . 42
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 . 69
Table 13 – Values of insulation resistance . 72
Table 14 – Table of dielectric strength test voltages. 73
Table 15 – Limits for currents . 76
Table 16 – Nominal cross-sectional areas of external flexible cables or cords . 95
– 8 – IEC 61558-2-8:2024 EXV IEC 2024
Table 17 – Pull and torque to be applied to external flexible cables or cords fixed to
stationary and portable transformers . 99
Table 18 – Torque to be applied to screws and connections . 104
Table 19 – Torque test on glands . 105
Table 20 – Clearances in mm . 112
Table 21 – Creepage distances in mm . 113
Table 22 – Distance through insulation in mm . 114
Table 23 – Creepage distances and clearance between terminals for external
connection . 115
Table 24 – Values of FIW wires with minimum overall diameter and minimum test
voltages according to the total enamel increase . 117
Table A.1 – Width of groove values depending on the pollution degree . 124
Table F.1 – Peak surge current of additional loads. 134
Table I.1 – Dimensions of rectangular copper connectors . 141
Table K.1 – Mandrel diameter . 145
Table K.2 – Oven temperature . 145
Table Q.1 – Degrees of protection against access to hazardous parts indicated by the
first characteristic numeral . 159
Table Q.2 – Degrees of protection against solid foreign objects indicated by the first
characteristic numeral . 159
Table Q.3 – Degrees of protection indicated by the second characteristic numeral . 160
Table R.1 – Impulse test voltage according to 6.1.2.2.1 of IEC 60664-1:2007 . 161
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF TRANSFORMERS, REACTORS,
POWER SUPPLY UNITS AND COMBINATIONS THEREOF –
Part 2-8: Particular requirements and tests for transformers
and power supply units for bells and chimes
FOREWORD
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This extended version (EXV) of the official IEC Standard provides the user with the
comprehensive content of the Standard.
made to IEC 61558-1:2017.
The specific content of IEC 61558-2-8:2024 is displayed on a blue background.
– 10 – IEC 61558-2-8:2024 EXV IEC 2024
IEC 61558-2-8 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) new symbol for power supply unit with linearly regulated output voltage.
The text of this document is based on the following documents:
Draft Report on voting
96/592/FDIS 96/598/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
...
IEC 61558-2-8 ®
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 2-8: Particular requirements and tests for transformers and power supply
units for bells and chimes
Sécurité des transformateurs, bobines d'inductance, blocs d'alimentation et des
combinaisons de ces éléments –
Partie 2-8 : Exigences particulières et essais pour les transformateurs et blocs
d'alimentation pour sonneries et carillons
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
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IEC 61558-2-8 ®
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 2-8: Particular requirements and tests for transformers and power supply
units for bells and chimes
Sécurité des transformateurs, bobines d'inductance, blocs d'alimentation et des
combinaisons de ces éléments –
Partie 2-8 : Exigences particulières et essais pour les transformateurs et blocs
d'alimentation pour sonneries et carillons
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.180 ISBN 978-2-8322-8974-7
– 2 – IEC 61558-2-8:2024 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 . 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. 15
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
Annex F (normative) Requirements for manually operated switches which are parts of
transformers assembly . 17
Bibliography . 18
Table 101 – Symbols indicating the kind of transformer . 10
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SAFETY OF TRANSFORMERS, REACTORS,
POWER SUPPLY UNITS AND COMBINATIONS THEREOF –
Part 2-8: Particular requirements and tests for transformers
and power supply units for bells and chimes
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 61558-2-8 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) new symbol for power supply unit with linearly regulated output voltage.
– 4 – IEC 61558-2-8:2024 IEC 2024
The text of this document is based on the following documents:
Draft Report on voting
96/592/FDIS 96/598/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 bells and chimes.
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 61558-2-8:2024 IEC 2024
SAFETY OF TRANSFORMERS, REACTORS,
POWER SUPPLY UNITS AND COMBINATIONS THEREOF –
Part 2-8: Particular requirements and tests for transformers
and power supply units for bells and chimes
1 Scope
Replacement:
This part of IEC 61558 deals with the safety of bell and chime transformers and power supply
units incorporating bell and chime transformers. 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 bell and chime
transformers and power supply units incorporating bell and chime transformers.
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 take precedence.
This document is applicable to stationary, 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 250 V AC and the rated supply frequency and the
internal operating frequencies do not exceed 500 Hz.
The rated output does not exceed 100 VA.
The no-load output voltage does not exceed 33 V AC or 46 V ripple-free DC, and the rated
output voltage does not exceed 24 V AC, or 33 V ripple-free DC.
Bell and chime transformers are generally intended to supply domestic sound signalling
equipment and other similar devices where the load is applied for short periods of time.
NOTE 2 A partial load can be applied for illumination purposes.
This document is not applicable to external circuits and their components intended to be
connected to the input terminals and output terminals of the transformers.
NOTE 3 Transformers covered by this document are only used in applications where double or reinforced
insulation between circuits is required by the installation rules or by the end product standard.
NOTE 4 Normally the transformers are intended to be used with equipment to provide voltages different from the
supply voltage for the functional requirements of the equipment. The protection against electric shock can be provided
or completed by other features of the equipment, such as the body. Parts of output circuits can be connected to
the input circuits or to protective earthing.
This document is applicable to transformers associated with specific equipment, to the extent
decided upon by the relevant IEC technical committees.
Attention is drawn to the following, if necessary:
– 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
This clause of IEC 61558-1:2017 is applicable except as follows:
Addition:
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
bell and chime transformer
single-phase safety isolating transformer specifically intended to supply household sound
signalling equipment and other similar devices
– 8 – IEC 61558-2-8:2024 IEC 2024
4 General requirements
This clause of IEC 61558-1:2017 is applicable.
5 General notes on tests
This clause of IEC 61558-1:2017 is applicable.
6 Ratings
This clause of IEC 61558-1:2017 is applicable except as follows:
Addition:
6.101 The rated output voltage shall not exceed 24 V AC or 33 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 100 VA.
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 250 V AC.
Compliance with the requirements of 6.101 to 6.104 is checked by inspection of the marking.
7 Classification
This clause of IEC 61558-1:2017 is applicable except as follows:
7.2
Replacement:
7.2 Transformers are classified according to the short-circuit characteristic or protection
against abnormal use:
– inherently short-circuit proof transformers;
– non-inherently short-circuit proof transformers;
– fail-safe transformers.
7.4
Replacement:
7.4 Transformers are classified according to their mobility:
– fixed transformers.
7.5
Replacement:
7.5 Transformers are classified according to their duty-type:
– short-time duty cycle;
– intermittent duty cycle.
NOTE 1 A partial load for illumination can be applied continuously.
7.8
Replacement:
7.8 Transformers are classified according to their transient overvoltage condition:
– overvoltage category II
Addition:
7.101 Transformers are classified according to the method of mounting:
– mounting in a distribution assembly;
– mounting in sound signalling devices (bells, chimes, buzzers, etc.);
– mounting on an outlet box or cabinet;
– flush mounted;
– surface mounted.
8 Marking and other information
This clause of IEC 61558-1:2017 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.
– 10 – IEC 61558-2-8:2024 IEC 2024
Table 101 – Symbols indicating the kind of transformer
Symbol or graphical symbol Explanation or title Identification
Fail-safe bell and chime transformer IEC 60417-5013:2002-10
modified
Short-circuit-proof bell and chime transformer IEC 60417-5013:2002-10
(inherently or non-inherently)
Power supply unit, linear IEC 60417-6210:2013-10
9 Protection against electric shock
This clause of IEC 61558-1:2017 is applicable except as follows:
Addition:
9.101 Protection against accidental contact with windings and hazardous live parts of the
input circuit shall be ensured while connecting conductors to the output terminals.
Compliance is checked by inspection and by the application of the standard test finger shown
in Figure 4. It shall not be possible to touch windings or hazardous live parts of the input
circuit with the test finger.
10 Change of input voltage setting
This clause of IEC 61558-1:2017 is applicable.
11 Output voltage and output current under load
This clause of IEC 61558-1:2017 is applicable except as follows:
11.1
Replacement:
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 shall not differ from
the rated value by more than:
a) 15 % for the output voltage of inherently short-circuit proof transformers with one rated
output voltage;
b) 15 % for the highest output voltage of inherently short-circuit proof transformers with
more than one rated output voltage;
c) 20 % for the other output voltages of inherently short-circuit proof transformers with
more than one rated output voltage;
d) 15 % for the output voltages of other transformers.
Compliance is checked by measuring the output voltage 2 min after 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 the rated power
factor.
For transformers with more than one rated supply voltage, the requirement is applicable for
each of the rated supply voltages.
For transformers with multiple output windings, the loads are applied to every multiple section
simultaneously, unless otherwise declared.
12 No-load output voltage
This clause of IEC 61558-1:2017 is applicable except as follows:
Addition:
12.101 The no-load output voltage shall not exceed 33 V AC or 46 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 100 %.
– 12 – IEC 61558-2-8:2024 IEC 2024
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
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
This clause of IEC 61558-1:2017 is applicable.
14 Heating
This clause of IEC 61558-1:2017 is applicable except as follows:
14.1.1 Temperature-rise test
Replacement of the third paragraph:
Temperatures are determined under the following conditions.
Replacement of the eleventh paragraph:
Transformers are supplied at rated supply voltage and loaded with an impedance Z producing
rated output at the rated output voltage and, for AC current, at the rated power factor. The
value of output current is measured after 1 min. Then the supply voltage is increased by 10 %
and the output impedance is adjusted so that the new impedance Z’ gives the same output
current than the value measured before. Transformers are submitted to 20 cycles of 1 min
operation with the impedance Z’ and 5 min operation with 5 times the impedance Z’.
Temperature rises are measured during the last cycle.
14.1.3 Determination of steady-state conditions
Addition of the following footnote “g“ in Table 2 to "External enclosures":
g The external enclosure of a transformer only includes the parts accessible to the standard test finger when
mounted in accordance with 14.1.1.
Addition of the following footnote “h“ in Table 2 to "Supports":
h Support includes any area of the black painted plywood support, but excludes any metal parts of the mounting
system (rails, outlet boxes, etc.).
15 Short-circuit and overload protection
This clause of IEC 61558-1:2017 is applicable except as follows:
Addition:
15.101 The maximum short-circuit output current shall not exceed 10 A, measured 5 s after
applying the short-circuit, the transformer being supplied with 1,1 times the rated supply
voltage.
16 Mechanical strength
This clause of IEC 61558-1:2017 is applicable except as follows:
16.2 Stationary transformers
Replacement:
The impact hammer shall have an energy of (0,2 ± 0,05) J.
17 Protection against harmful ingress of dust, solid objects and moisture
This clause of IEC 61558-1:2017 is applicable.
18 Insulation resistance, dielectric strength and leakage current
This clause of IEC 61558-1:2017 is applicable.
19 Construction
This clause of IEC 61558-1:2017 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);
– 14 – IEC 61558-2-8:2024 IEC 2024
– 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 insulation
between the input windings and any intermediate conductive part shall consist of at least
basic insulation, and the insulation between the output windings and any intermediate
conductive part shall consist of at least supplementary insulation (both basic and
supplementary insulations rated for the working voltage).
NOTE 1 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).
NOTE 2 Basic insulation and supplementary insulation are interchangeable.
In addition, the following applies:
– for class I transformers, the insulation between the input and output windings via the
intermediate conductive parts (even if they are connected to earthing) 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 via
the intermediate conductive parts (if any) shall consist of double or reinforced
insulation (rated for the input voltage), and the insulation between the body and the
output windings via the intermediate conductive parts (if any) and the body via the
intermediate conductive parts shall consist of double or reinforced insulation (rated
for the input and output voltage);
– for transformers different from independent (IP00), the insulation between the input
and output windings via the intermediate conductive parts shall consist of double or
reinforced insulation (rated for the working voltage).
NOTE 3 In 19.1.2 the possibility to consider the intermediate metal part connected to earthing and consequently to
require basic insulation in both circuits (primary and secondary) is not allowed for the following reason:
– the intermediate metal part is normally the iron core made by laminated plates insulated to each other by oxide.
It is not assured that all foils are correctly connected to the earthing.
– for transformers different from independent, it is not assured that in the final applications the iron core will be
connected to earthing.
Addition:
19.101 There shall be no connections between the output circuit and the protective earthing,
unless allowed by the relevant equipment standard for associated transformers.
19.102 There shall be no connections between the output circuit and the body, unless this
is allowed by the relevant equipment standard for associated transformers.
Compliance is checked by inspection.
19.103 These 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.
20 Components
This clause of IEC 61558-1:2017 is applicable. except as follows:
20.4
Modification:
20.4 If the transformer incorporates a switch intended to disconnect the input winding from
the supply, this switch can be of single-pole micro-gap construction and can disconnect either
pole.
21 Internal wiring
This clause of IEC 61558-1:2017 is applicable.
22 Supply connection and other external flexible cables or cords
This clause of IEC 61558-1:2017 is applicable except as follows:
22.3
Replacement of the first paragraph as follows:
22.3 Flush-type transformers can be designed so that connection of the external conductors
to the terminals are made before the transformer is fitted into a flush mounting box.
22.5
Replacement:
22.5 Power supply cords of transformers shall be at least ordinary polyvinyl chloride
sheathed flexible cords according to IEC 60227-5:2011 – type 60227 IEC 53 or ordinary tough
rubber sheathed flexible cords according to IEC 60245-4:2011 – type 60245 IEC 53.
23 Terminals for external conductors
This clause of IEC 61558-1:2017 is applicable.
24 Provisions for protective earthing
This clause of IEC 61558-1:2017 is applicable.
– 16 – IEC 61558-2-8:2024 IEC 2024
25 Screws and connections
This clause of IEC 61558-1:2017 is applicable except as follows:
25.3
Addition:
This requirement is not applicable to electrical connections other than protective earthing
connections on the output circuits of the transformers with a rated output not exceeding
12 VA.
26 Creepage distances, clearances and distances through insulation
This clause of IEC 61558-1:2017 is applicable.
27 Resistance to heat, fire and tracking
This clause of IEC 61558-1:2017 is applicable.
28 Resistance to rusting
This clause of IEC 61558-1:2017 is applicable.
Annexes
The annexes of IEC 61558-1:2017 are applicable except as follows:
Annex F
(normative)
Requirements for manually operated switches
which are parts of transformers assembly
This annex of IEC 61558-1:2017 is applicable except as follows:
F.2 Switches tested as a separate component
Addition of a third bullet point after the first paragraph of Clause F.2:
• 7.4.7: the number of operating cycles shall be 1 000.
– 18 – IEC 61558-2-8:2024 IEC 2024
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 61058-1:2016, Switches for appliances – Part 1: General requirements
IEC 61558 (all parts), Safety of transformers, reactors, power supply units and combinations
thereof
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
ISO/IEC GUIDE 51:2014, Safety aspects – Guidelines for their inclusion in standards
____________
– 20 – IEC 61558-2-8:2024 IEC 2024
SOMMAIRE
AVANT-PROPOS . 21
INTRODUCTION . 24
1 Domaine d'application . 25
2 Références normatives . 26
3 Termes et définitions . 27
4 Exigences générales . 27
5 Généralités sur les essais. 27
6 Caractéristiques assignées . 27
7 Classification . 28
8 Marquage et indications . 29
9 Protection contre les chocs électriques . 29
10 Changement de la tension primaire d’alimentation . 30
11 Tension secondaire et courant secondaire en charge . 30
12 Tension secondaire à vide . 30
13 Tension de court-circuit . 31
14 Échauffements. 31
15 Protection contre les courts-circuits et les surcharges . 32
16 Résistance mécanique . 32
17 Protection contre les effets nuisibles dus à la pénétration de poussière, d’objets
solides et de l’humidité . 32
18 Résistance d'isolement, rigidité diélectrique et courant de fuite . 32
19 Construction . 32
20 Composants . 34
21 Conducteurs internes. 34
22 Raccordement à l’alimentation et câbles souples externes . 34
23 Bornes pour conducteurs externes . 35
24 Dispositions en vue de la mise à la terre de protection . 35
25 Vis et connexions .
...
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