IEC 60947-4-2:2020

IEC 60947-4-2 ®
Edition 4.1 2024-11
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
colour
inside
Low-voltage switchgear and controlgear –
Part 4-2: Contactors and motor-starters – Semiconductor motor controllers,
starters and soft-starters
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IEC 60947-4-2 ®
Edition 4.1 2024-11
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
colour
inside
Low-voltage switchgear and controlgear –
Part 4-2: Contactors and motor-starters – Semiconductor motor controllers,
starters and soft-starters
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.130.20 ISBN 978-2-8327-0000-6
REDLINE VERSION – 2 – IEC 60947-4-2:2020+AMD1:2024 CSV
© IEC 2024
CONTENTS
FOREWORD . 7
INTRODUCTION . 9
1 Scope . 10
2 Normative references . 11
3 Terms, definitions, symbols and abbreviated terms . 12
3.1 Terms and definitions . 12
3.1.1 Terms and definitions concerning the types of semiconductor motor
controllers and starters . 12
3.1.2 Terms and definitions concerning semiconductor motor controllers and
starters . 14
3.1.3 Terms and definitions concerning safety aspects . 17
3.1.4 Alphabetical index of terms . 18
3.2 Symbols and abbreviated terms . 20
4 Classification . 20
5 Characteristics of semiconductor motor controllers and starters . 20
5.1 Summary of characteristics . 20
5.2 Type of equipment . 21
5.2.1 Kind of equipment . 21
5.2.2 Number of poles . 21
5.2.3 Kind of current . 21
5.2.4 Interrupting medium (air, vacuum, etc.) . 21
5.2.5 Operating conditions of the equipment . 21
5.3 Rated and limiting values for main circuits . 22
5.3.1 Rated voltages . 22
5.3.2 Currents. 24
5.3.3 Rated frequency . 25
5.3.4 Duty cycle values and sequences . 25
5.3.5 Normal load and overload characteristics . 25
5.3.6 Rated conditional short-circuit current . 27
5.3.7 Semiconductor motor controller power losses . 27
5.4 Utilization category . 28
5.4.1 General. 28
5.4.2 Assignment of ratings based on the results of tests . 28
5.5 Control circuits . 29
5.6 Auxiliary circuits . 29
5.7 Characteristics of relays and releases (overload relays). 29
5.7.1 Summary of characteristics . 29
5.7.2 Types of relay or release . 30
5.7.3 Characteristic values . 30
5.7.4 Designation and current settings of overload relays . 31
5.7.5 Time-current characteristics of overload relays . 31
5.7.6 Influence of ambient air temperature . 32
5.8 Coordination with short-circuit protective devices (SCPD) . 32
6 Product information . 32
6.1 Nature of information . 32
6.2 Marking . 34

© IEC 2024
6.3 Instructions for installation, operation, maintenance, decommissioning and
dismantling . 34
6.4 Environmental information . 34
7 Normal service, mounting and transport conditions . 35
7.1 Normal service conditions . 35
7.1.1 Ambient air temperature . 35
7.1.2 Altitude . 35
7.1.3 Atmospheric conditions . 35
7.1.4 Shock and vibrations. 35
7.2 Conditions during transport and storage . 36
7.3 Mounting . 36
7.4 Electrical system disturbances and influences . 36
8 Constructional and performance requirements . 36
8.1 Constructional requirements . 36
8.1.1 General. 36
8.1.2 Materials . 37
8.1.3 Current-carrying parts and their connections . 37
8.1.4 Clearances and creepage distances . 37
8.1.5 Actuator . 37
8.1.6 Indication of the contact position . 37
8.1.7 Additional requirements for equipment suitable for isolation . 38
8.1.8 Terminals . 38
8.1.9 Additional requirements for equipment provided with a neutral pole . 38
8.1.10 Provisions for protective earthing . 38
8.1.11 Enclosures for equipment . 38
8.1.12 Degrees of protection of enclosed equipment. 38
8.1.13 Conduit pull-out, torque and bending with metallic conduits . 38
8.1.14 Limited energy source . 38
8.1.15 Stored charge energy circuit . 41
8.1.16 Fault and abnormal conditions . 41
8.1.17 Short-circuit and overload protection of ports . 42
8.2 Performance requirements . 42
8.2.1 Operating conditions . 42
8.2.2 Temperature-rise . 46
8.2.3 Dielectric properties . 48
8.2.4 Normal load and overload performance requirements . 49
8.2.5 Coordination with short-circuit protective devices . 54
8.3 EMC requirements . 54
8.3.1 General. 54
8.3.2 Immunity . 55
8.3.3 Emission . 57
9 Tests . 57
9.1 Kinds of tests . 57
9.1.1 General. 57
9.1.2 Type tests . 57
9.1.3 Routine tests . 58
9.1.4 Sampling tests . 58
9.1.5 Special tests . 58
9.2 Compliance with constructional requirements . 59

REDLINE VERSION – 4 – IEC 60947-4-2:2020+AMD1:2024 CSV
© IEC 2024
9.2.1 General. 59
9.2.2 Electrical performance of screwless-type clamping units . 59
9.2.3 Ageing test for screwless-type clamping units . 60
9.2.4 Limited energy source test . 60
9.2.5 Breakdown of components . 60
9.2.6 Wire flexing test . 61
9.2.7 Abnormal operating tests . 61
9.3 Compliance with performance requirements . 63
9.3.1 Test sequences . 63
9.3.2 General test conditions . 64
9.3.3 Performance under no load, normal load, and overload conditions . 64
9.3.4 Performance under short-circuit conditions . 74
9.4 EMC tests . 77
9.4.1 General. 77
9.4.2 EMC immunity tests . 78
9.4.3 EMC emission tests . 79
9.5 Routine and sampling tests . 82
9.5.1 General. 82
9.5.2 Operation and operating limits . 82
9.5.3 Dielectric tests . 82
Annex A (normative) Marking and identification of terminals . 84
A.1 General . 84
A.2 Marking and identification of terminals of semiconductor controllers and
starters . 84
A.2.1 Marking and identification of terminals of main circuits . 84
A.2.2 Marking and identification of terminals of control circuits. 84
A.3 Marking and identification of terminals of overload relays . 84
Annex B (xxx) . 85
Annex C (normative) Coordination at the crossover current between the starter and
associated SCPD . 86
C.1 General and definitions . 86
C.1.1 General. 86
C.1.2 Terms and definitions . 86
C.2 Condition for the test for the verification of coordination at the crossover
current by a direct method . 86
C.3 Test currents and test circuits . 86
C.4 Test procedure and results to be obtained . 87
C.4.1 Test procedure . 87
C.4.2 Results to be obtained . 87
C.5 Verification of coordination at the crossover current by an indirect method
for type "2" coordination . 87
C.5.1 General. 87
C.5.2 Test for I . 87
cd
C.5.3 Time-current characteristic withstand capability of controllers/starters . 88
Annex D (xxx) . 90
Annex E (xxx) . 91
Annex F (informative) Operating capability . 92
Annex G (informative) Rated operational currents and rated operational powers of
switching devices for electrical motors . 96

© IEC 2024
G.1 General . 96
G.2 Rated operational powers and rated operational currents . 96
Annex H (xxx) . 100
Annex I (normative) Modified test circuit for short-circuit testing of semiconductor
motor controllers and starters . 101
Annex J (xxx) . 103
Annex K (xxx) . 104
Annex L (normative) Examples of overvoltage category reduction . 105
L.1 General . 105
L.2 Insulation to the surroundings . 105
L.2.1 Circuits connected directly to the supply mains . 105
L.2.2 Insulation between circuits . 106
Annex M (xxx) . 110
Annex N (normative) Additional requirements and tests for equipment with protective
separation . 111
N.1 General . 111
N.2 Definitions. 111
N.3 Requirements . 111
N.3.1 Test method for implementing protective impedance . 111
N.3.2 Touch current measurement . 112
Bibliography . 114

Figure 1 – Semiconductor motor control devices . 13
Figure 2 – Connecting methods . 24
Figure 3 – Thermal memory test . 44
Figure 4 – Multiple of current setting limits for ambient air temperature compensated
time-delay overload relays . 74
Figure C.1 – Examples of time-current withstand characteristic. 89
Figure F.1 – Thermal stability test profile . 93
Figure F.2 – Overload capability test profile . 94
Figure F.3 – Blocking and commutating capability test profile . 95
Figure I.1 – Modified circuit for short-circuit testing of semiconductor devices . 101
Figure I.2 – Time line for the short-circuit test of 9.3.4.1.6 . 102
Figure L.1 – Basic insulation evaluation for circuits connected directly to the origin of
the installation mains supply . 105
Figure L.2 – Basic insulation evaluation for circuits connected directly to the mains
supply . 106
Figure L.3 – Basic insulation evaluation for equipment not permanently connected to
the mains supply . 106
Figure L.4 – Basic insulation evaluation for insulation between circuits connected
directly to the origin of the installation mains supply and that are declared galvanically
separated . 107
Figure L.5 – Basic insulation evaluation for insulation between circuits connected
directly to the mains supply and that are declared galvanically separated . 107
Figure L.6 – Basic insulation evaluation for insulation between circuits not permanently
connected directly to the mains supply and that are declared galvanically separated . 108

REDLINE VERSION – 6 – IEC 60947-4-2:2020+AMD1:2024 CSV
© IEC 2024
Figure L.7 – Basic insulation evaluation for insulation between circuits connected
directly to the origin of the installation mains supply and that are declared galvanically
separated where internal SPDs are used . 108
Figure L.8 – Basic insulation evaluation for insulation between circuits connected
directly to the mains supply and that are declared galvanically separated where
internal SPDs are used . 109
Figure L.9 – Basic insulation evaluation for insulation between circuits connected
directly to the mains supply and that are declared galvanically separated . 109
Figure N.1 – Protection by means of protective impedance . 112
Figure N.2 – Measuring instrument . 113

Table 1 – Utilization categories . 28
Table 2 – Relative levels of severity . 29
Table 3 – Trip classes of overload relays . 31
Table 19 – Limits for limited energy sources without an over-current protective device . 39
Table 20 – Limits for limited energy sources with an over-current protective device . 40
Table 21 – Limits for limited energy source with current limiting impedance . 40
Table 4 – Limits of operation of time-delay overload relays when energized on all poles . 44
Table 5 – Limits of operation of three-pole time-delay overload relays when energized
on two poles only . 45
Table 6 – Temperature-rise limits for insulated coils in air and in oil . 47
Table 7 – Minimum overload current withstand time (T ) in relation to overload current
x
ratio (X) and corresponding to overload relay trip class (see Table 3) . 49
Table 8 – Minimum requirements for thermal stability test conditions . 50
Table 9 – Prospective locked rotor current by utilization categories . 51
Table 10 – Minimum requirements for overload capability test conditions . 51
Table 11 – Making and breaking capacity test; making and breaking conditions
according to utilization categories for the mechanical switching device . 53
Table 12 – Conventional operational performance making and breaking conditions
according to utilization categories for the mechanical switching device . 53
Table 13 – Specific performance criteria when EM disturbances are present . 56
Table 14 – Thermal stability test specifications . 68
Table 15 – Initial case temperature requirements . 69
Table 16 – Minimum requirements and conditions for performance testing with an
induction motor load . 71
Table 17 – Terminal disturbance voltage limits for conducted radio-frequency emission
(AC mains power port) . 81
Table 18 – Radiated emissions test limits . 82
Table A.1 – Main circuit terminal markings . 84
Table C.1 – Test conditions . 88
Table G.1 – Rated operational powers and rated operational currents of motors . 97
Table L.1 – Drawing keys . 105

© IEC 2024
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
LOW-VOLTAGE SWITCHGEAR AND CONTROLGEAR –

Part 4-2: Contactors and motor-starters –
Semiconductor motor controllers, starters and soft-starters

AMENDMENT 1
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
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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
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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 [and/or] www.iso.org/patents. IEC shall not be held responsible for identifying any or all
such patent rights.
This consolidated version of the official IEC Standard and its amendment has been
prepared for user convenience.
IEC 60947-4-2 edition 4.1 contains the fourth edition (2020-06) [documents
121A/353/FDIS and 121A/360/RVD] and its amendment 1 (2024-11) [documents
121A/615/FDIS and 121A/626/RVD].
In this Redline version, a vertical line in the margin shows where the technical content
is modified by amendment 1. Additions are in green text, deletions are in strikethrough

REDLINE VERSION – 8 – IEC 60947-4-2:2020+AMD1:2024 CSV
© IEC 2024
red text. A separate Final version with all changes accepted is available in this
publication.
International Standard IEC 60947-4-2 has been prepared by subcommittee 121A: Low-voltage
switchgear and controlgear, of IEC technical committee 121: Switchgear and controlgear and
their assemblies for low voltage.
This fourth edition cancels and replaces the third edition published in 2011. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
• scope exclusions;
• editorial correction of notes and hanging paragraphs;
• reference to IEC 62683-1;
• safety aspects related to:
– general aspects;
– limited energy circuits;
– electronic circuits;
• mention of dedicated wiring accessories;
• power consumption measurement;
• alignment to IEC 60947-1:2020.
The provisions of the general rules dealt with IEC 60947-1 are applicable to this part of
IEC 60947 series where specifically called for. Clauses and subclauses, tables, figures and
annexes of the general rules thus applicable are identified by reference to IEC 60947-1:2020.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all the parts in the IEC 60947 series, under the general title Low-voltage switchgear
and controlgear, can be found on the IEC website.
The committee has decided that the contents of this document and its amendment 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 publication 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.
© IEC 2024
INTRODUCTION
This document covers low-voltage semiconductor motor controllers, starters and soft-starters
that have many capabilities and features beyond the simple starting and stopping of an
induction motor, such as controlled starting and stopping, manoeuvring and controlled
running.
The generic term “controller” is used in this document wherever reference is made to
elements of power semiconductor switching devices.
The generic term “starter” is used in this document wherever reference is made to the
elements of power semiconductor switching devices together with suitable overload protective
devices.
REDLINE VERSION – 10 – IEC 60947-4-2:2020+AMD1:2024 CSV
© IEC 2024
LOW-VOLTAGE SWITCHGEAR AND CONTROLGEAR –

Part 4-2: Contactors and motor-starters –
Semiconductor motor controllers, starters and soft-starters

1 Scope
This part of IEC 60947 applies to semiconductor motor controllers, starters and soft-starters
which can include a series mechanical switching device, intended to be connected to circuits
the rated voltage of which does not exceed 1 000 V AC.
This document characterizes semiconductor motor controllers and starters with and without
bypass means.
This document does not apply to:
– semiconductor motor controllers and starters used for continuous operation of AC motors
at motor speeds other than the normal speed ;
– electromechanical contactors and external overload relays (see IEC 60947-4-1);
– short-circuit protective device associated with semiconductor motor controllers and
starters (see IEC 60947-4-1 (MPSD), IEC 60947-2 and IEC 60947-3);
– semiconductor equipment, including semiconductor contactors (3.4.13 of
IEC 60947-1:2020) controlling non-motor loads (see IEC 60947-4-3);
– semiconductor motor controllers and starters used for rotor circuits ;
– adjustable speed electrical power drive systems (see IEC 61800 series);
– use of the product within explosive atmospheres (see IEC 60079 series);
– software and firmware requirements ;
NOTE 1 Guidance on embedded software is given in IEC TR 63201.
– cyber security aspects (see IEC TS 63208).
Contactors, overload relays and control circuit devices used in semiconductor motor
controllers and starters are considered compliant with the requirements of their relevant
product standard. Where mechanical switching devices are used, they are considered meeting
the requirements of their own IEC product standard, and the additional requirements of this
document.
The object of this document is to state as follows:
– the characteristics of semiconductor motor controllers, starters and soft-starters and
associated equipment;
– the conditions with which semiconductor motor controllers, starters and soft-starters
comply with reference to
a) their operation and behaviour in normal and abnormal operating conditions including
overcurrent operating conditions;
b) their dielectric properties;
c) the degrees of protection provided by their enclosures where applicable;
____________
For this subject, the manufacturer is responsible for taking additional safety measures.

© IEC 2024
d) their construction including safety measures against electric shock, fire hazard and
mechanical hazard;
– the tests intended for confirming that these conditions have been met, and the methods to
be adopted for these tests;
– the information to be given with the equipment, or in the manufacturer's literature.
NOTE 2 For the purpose of this document, the term "controller" is used instead of "semiconductor motor
controller".
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60034-1:2017, Rotating electrical machines – Part 1: Rating and performance
IEC 60445:2021, Basic and safety principles for man-machine interface, marking and
identification – Identification of equipment terminals, conductor terminations and conductors
IEC 60715, Dimensions of low-voltage switchgear and controlgear – Standardized mounting
on rails for mechanical support of switchgear, controlgear and accessories
IEC 60730-1, Automatic electrical controls – Part 1: General requirements
IEC 60947-1:2020, Low-voltage switchgear and controlgear – Part 1: General rules
IEC 61000-3-2, Electromagnetic compatibility (EMC) – Part 3-2: Limits – Limits for harmonic
current emissions (equipment input current ≤16 A per phase)
IEC 61000-3-3, Electromagnetic compatibility (EMC) – Part 3-3: Limits – Limitation of voltage
changes, voltage fluctuations and flicker in public low-voltage supply systems, for equipment
with rated current ≤16 A per phase and not subject to conditional connection
IEC 61000-3-11, Electromagnetic compatibility (EMC) – Part 3-11: Limits – Limitation of
voltage changes, voltage fluctuations and flicker in public low-voltage supply systems –
Equipment with rated current ≤ 75 A and subject to conditional connection
IEC 61000-3-12, Electromagnetic compatibility (EMC) – Part 3-12: Limits – Limits for
harmonic currents produced by equipment connected to public low-voltage systems with input
current >16 A and ≤ 75 A per phase
IEC 61140:2016, Protection against electric shock – Common aspects for installation and
equipment
IEC 63404:2024, Switchgear and controlgear and their assemblies for low voltage –
Integration of radiocommunication device above 380 MHz into an equipment
IEC TS 63058, Environmental aspects for low-voltage switchgear and controlgear and their
assemblies
CISPR 11:2015, Industrial, scientific and medical equipment – Radio-frequency disturbance
characteristics – Limits and methods of measurement
CISPR 11:2015/AMD1:2016
REDLINE VERSION – 12 – IEC 60947-4-2:2020+AMD1:2024 CSV
© IEC 2024
ISO 2859-1:1999, Sampling procedures for inspection by attributes – Part 1: Sampling
schemes indexed by acceptance quality limit (AQL) for lot-by-lot inspection
3 Terms, definitions, symbols and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60947-1:2020, as
well as the following terms, definitions, symbol and abbreviations apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• ISO Online browsing platform: available at https://www.iso.org/obp
• IEC Electropedia: available at http://www.electropedia.org/
3.1.1 Terms and definitions concerning the types of semiconductor motor controllers
and starters
3.1.1.1
semiconductor switching device
switching device designed to make and/or break the current in an electric circuit by means of
the controlled conductivity of a semiconductor
Note 1 to entry: This definition differs from IEC 60050-441:1984, 441-14-03 since a semiconductor switching
device is also designed for breaking the current.
[SOURCE: IEC 60947-1:2020, 3.4.3, modified – Note 1 to entry added.]
3.1.1.2
semiconductor controller
semiconductor switching device that provides a switching function for an AC electrical load
and an OFF-state
Note 1 to entry: Because hazardous levels of the OFF-state current (3.1.2.12) exist in a semiconductor controller,
the load terminals should be considered as live parts at all times.
Note 2 to entry: In a circuit where the current passes through zero (alternately or otherwise), the effect of "not
making" the current following such a zero value is equivalent to breaking the current.
Note 3 to entry: See 3.4.3 of IEC 60947-1:2020 for the definition of semiconductor switching device.
Note 4 to entry: This device can include internal electromechanical switching device(s) bypassing or in series with
the semiconductor at the manufacturer’s discretion.
3.1.1.3
semiconductor motor controller
semiconductor contr
...