IEC 62271-106:2021

IEC 62271-106 ®
Edition 2.0 2021-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
High-voltage switchgear and controlgear –
Part 106: Alternating current contactors, contactor-based controllers and
motorstarters
Appareillage à haute tension –
Partie 106: Contacteurs, combinés de démarrage à contacteurs et démarreurs de
moteurs, pour courant alternatif

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IEC 62271-106 ®
Edition 2.0 2021-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
High-voltage switchgear and controlgear –

Part 106: Alternating current contactors, contactor-based controllers and

motorstarters
Appareillage à haute tension –

Partie 106: Contacteurs, combinés de démarrage à contacteurs et démarreurs

de moteurs, pour courant alternatif

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.130.10 ISBN 978-2-8322-1034-4

– 2 – IEC 62271-106:2021  IEC 2021
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 7
3 Terms and definitions . 8
4 Normal and special service conditions . 23
5 Ratings . 24
6 Design and construction . 38
7 Type tests . 42
8 Routine tests . 70
9 Guide to the selection of contactors and motor-starters for service (informative) . 72
10 Information to be given with enquiries, tenders and orders (informative) . 76
11 Transport, storage, installation, operating instructions and maintenance. 78
12 Safety . 78
13 Influence of the product on the environment . 78
Annex A (normative) Identification of test objects . 79
Annex B (informative) Determination of the equivalent RMS value of a short-time
current during a short-circuit of a given duration . 80
Annex C (normative) Method for weatherproofing test for outdoor switchgear and
controlgear . 81
Annex D (informative) References for auxiliary and control circuit components . 82
Annex E (normative) Tolerances on test quantities during tests . 83
Annex F (informative) Information and technical requirements to be given with
enquires, tenders and orders . 88
Annex G (informative) List of symbols and abbreviations . 89
Annex H (informative) Electromagnetic compatibility on site . 90
Annex I (informative) List of notes concerning certain countries . 91
Annex J (informative) Extension of validity type tests . 92
Annex K (informative) Exposure to pollution . 93
Annex AA (normative) Records and reports of type tests for making, breaking and
short-time current performance . 94
Annex BB (normative) Disconnectors and earthing switches used in controllers . 98
Bibliography . 100

Figure 1 – Examples of speed/time curves . 32
Figure 2 – Representation by two parameters of a prospective TRV of a circuit . 60
Figure 3 – Representation of the specified TRV by a two-parameter reference line and
a delay line . 60
Figure 4 – Determination of power-frequency recovery voltage . 61
Figure 5 – Test duties A and B – preferred earth point . 63
Figure 6 – Test duties A and B – alternative earth point . 64
Figure 7 – Test duty C – preferred earth point . 64
Figure 8 – Test duty C – alternative earth point . 65
Figure 9 – Characteristics for determining take-over current . 66

Figure BB.1 – Disconnector and earthing switch locations . 98

Table 1 – Ratings and characteristics . 25
Table 2 – Utilization categories . 31
Table 3 – Characteristics dependent on starter type . 37
Table 4 – Applicable type tests . 44
Table 5 – Intermittent duty operating cycles . 48
Table 6 – Verification of rated making and breaking capacities – Conditions for making
and breaking corresponding to the several utilization categories at rated voltage U . 52
r
Table 7 – Relationship between current broken I and OFF time . 55
c
Table 8 – Overload current withstand requirements . 56
Table 9 – Transient recovery voltage characteristics . 63
Table 10 – Verification of the number of on-load operating cycles – Conditions for

making and breaking corresponding to the several utilization categories . 68
Table E.101 – Tolerances on test quantities for type test . 83
Table G.101 – Additional list of symbols and abbreviations . 89

– 4 – IEC 62271-106:2021  IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
HIGH-VOLTAGE SWITCHGEAR AND CONTROLGEAR –

Part 106: Alternating current contactors,
contactor-based controllers and motor-starters

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
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
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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
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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) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent
rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62271-106 has been prepared by subcommittee 17A: Switching
devices, of IEC technical committee 17: High-voltage switchgear and controlgear.
This second edition cancels and replaces the first edition published in 2011. It constitutes a
technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
• document numbered to correspond to IEC 62271-1 2017.

The text of this International Standard is based on the following documents:
FDIS Report on voting
17A/1296/FDIS 17A/1301/RVD
Full information on the voting for the approval of this International Standard can be found in the
report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
This standard is to be read in conjunction with IEC 62271-1:2017. In order to simplify the
indication of corresponding requirements, the same numbering of clauses and subclauses is
used as in IEC 62271-1. Modifications to these clauses and subclauses are given under the
same numbering, whilst additional subclauses are numbered from 101.
A list of all parts of the IEC 62271 series under the general title, High-voltage switchgear and
controlgear, can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – IEC 62271-106:2021  IEC 2021
HIGH-VOLTAGE SWITCHGEAR AND CONTROLGEAR –

Part 106: Alternating current contactors,
contactor-based controllers and motor-starters

1 Scope
This part of IEC 62271 applies to AC contactors and/or contactor-based controllers and motor-
starters designed for indoor installation and operation at frequencies up to and including 60 Hz
on systems having voltages above 1 kV and up to and including 24 kV. This document also
includes additional requirements for outdoor installations where the equipment is housed in an
additional protective enclosure.
It is applicable only to three-pole devices for use in three-phase systems, and single-pole
devices for use in single-phase systems. Two-pole contactors and starters for use in single-phase
systems are subject to agreement between manufacturer and user.
Contactors and/or starters dealt with in this document typically do not have adequate
short-circuit interruption capability. In this context, this document gives requirements for:
– starters associated with separate short-circuit protective devices;
– controllers – contactors combined with short-circuit protective devices (SCPD).
Contactors intended for closing and opening electric circuits and, if combined with suitable
relays, for protecting these circuits against operating overloads are covered in this document.
This document is also applicable to the operating devices of contactors and to their auxiliary
equipment.
Motor-starters intended to start and accelerate motors to normal speed, to ensure continuous
operation of motors, to switch off the supply from the motor and to provide means for the
protection of motors and associated circuits against operating overloads are dealt with.
Motor-starter types included are:
– direct-on-line starters;
– reversing starters;
– two-direction starters;
– reduced kVA (voltage) starters;
• auto-transformer starters;
• rheostatic starters;
• reactor starters.
This document does not apply to:
– circuit-breaker-based motor-starters;
– single-pole operation of multi-pole contactors or starters;
– two-step auto-transformer starters designed for continuous operation in the starting position;
– unbalanced rheostatic rotor starters, i.e. where the resistances do not have the same value
in all phases;
– equipment designed not only for starting, but also for adjustment of speed;

– liquid starters and those of the "liquid-vapour" type;
– semiconductor contactors and starters making use of semiconductor contactors in the
main circuit;
– rheostatic stator starters;
– contactors or starters designed for special applications.
This document does not deal with components contained in contactors and contactor-based
motor-starters, for which individual specifications exist.
NOTE 1 Thermal electrical relays are covered by IEC 60255-149.
NOTE 2 High-voltage current-limiting fuses are covered by IEC 60282-1 and IEC 60644.
NOTE 3 Metal-enclosed switchgear and controlgear for rated voltages above 1 kV and up to and including 52 kV
are covered by IEC 62271-200.
NOTE 4 Disconnectors and earthing switches are covered by IEC 62271-102.
NOTE 5 High-voltage switches above 1 kV and less than 52 kV are covered by IEC 62271-103.
The object of this document is to state:
a) the characteristics of contactors and starters and associated equipment;
b) the conditions with which contactors or starters comply with reference to:
1) their operation and behaviour,
2) their dielectric properties,
3) the degrees of protection provided by their enclosures, where applicable,
4) their construction,
5) for controllers, interactions between the various components, for example SCPD
co-ordination;
c) the tests intended for confirming that these conditions have been met, and the methods to
be adopted for these tests;
d) the information to be given with the equipment or in the manufacturer's literature.
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 60060-1:2010, High-voltage test techniques – Part 1: General definitions and test
requirements
IEC 60068-2-1:2007, Environmental testing – Part 2-1: Tests – Test A: Cold
IEC 60068-2-2:2007, Environmental testing – Part 2-2: Tests – Test B: Dry heat
IEC 60068-2-30:2005, Environmental testing – Part 2-30: Tests – Test Db: Damp heat, cyclic
(12 h + 12 h cycle)
IEC 60076-2, Power transformers – Part 2: Temperature rise for liquid-immersed transformers
IEC 60076-11:2018, Power transformers – Part 11: Dry-type transformers

– 8 – IEC 62271-106:2021  IEC 2021
IEC 60255-21-1:1988, Electrical relays – Part 21: Vibration, shock, bump and seismic tests on
measuring relays and protection equipment – Section One: Vibration tests (sinusoidal)
IEC 60282-1, High-voltage fuses – Part 1: Current-limiting fuses
IEC 60417, Graphical symbols for use on equipment (available at http://www.graphical-
symbols.info/equipment)
IEC 60644, Specification for high-voltage fuse-links for motor circuit applications
IEC 60947-5-1, Low-voltage switchgear and controlgear – Part 5-1: Control circuit devices and
switching elements – Electromechanical control circuit devices
IEC 61000-4-18:2019, Electromagnetic compatibility (EMC) – Part 4-18: Testing and
measurement techniques – Damped oscillatory wave immunity test
IEC 61230, Live working – Portable equipment for earthing or earthing and short-circuiting
IEC 61812-1, Time relays for industrial use and residential use – Part 1: Requirements and
tests
IEC 62271-1:2017, High-voltage switchgear and controlgear – Part 1: Common specifications
for alternating current switchgear and controlgear
IEC 62271-100:2021, High-voltage switchgear and controlgear – Part 100: Alternating current
circuit-breakers
IEC 62271-102:2018, High-voltage switchgear and controlgear – Part 102: Alternating current
disconnectors and earthing switches
IEC 62271-110:2017, High-voltage switchgear and controlgear – Part 110: Inductive load
switching
IEC 62271-200:2021, High-voltage switchgear and controlgear – Part 200: AC metal-enclosed
switchgear and controlgear for rated voltages above 1 kV and up to and including 52 kV
3 Terms and definitions
For the purposes of this document, the terms and definitions given in Clause 3 of
IEC 62271-1:2017, as well as the following, apply.
3.1 General terms and definitions
Subclause 3.1 of IEC 62271-1: 2017 applies with the following additions:
3.1.101
controlgear
general term covering switching devices and their combination with associated control,
measuring, protective and regulating equipment, also assemblies of such devices and
equipment with associated interconnections, accessories, enclosures and supporting
structures, intended in principle for the control of electric energy consuming equipment
[SOURCE: IEC 60050-441:2000, 441-11-03]

3.1.102
overcurrent
current exceeding the rated current
[SOURCE: IEC 60050-441:2000, 441-11-06]
3.1.103
short-circuit current
over-current resulting from a short circuit due to a fault or an incorrect connection in an electric
circuit
[SOURCE: IEC 60050-441:2000, 441-11-07]
3.1.104
overload
operating conditions in an electrically undamaged circuit, which cause an over-current
[SOURCE: IEC 60050-441:2000, 441-11-08]
3.1.105
conductive part
part which is capable of conducting current although it may not necessarily be used for carrying
service current
[SOURCE: IEC 60050-441:2000, 441-11-09]
3.1.106
ambient air temperature
temperature, determined under prescribed conditions, of the air surrounding the complete
switching device or fuse
Note 1 to entry: For switching devices or fuses installed inside an enclosure, it is the temperature of the air outside
the enclosure.
[SOURCE: IEC 60050-441:2000, 441-11-13]
3.2 Assemblies of switchgear and controlgear
Subclause 3.2 of IEC 62271-1: 2017 applies.
3.3 Parts of assemblies
Subclause 3.3 of IEC 62271-1: 2017 applies.
3.4 Switching devices
Subclause 3.4 of IEC 62271-1: 2017 applies with the following modifications.
3.4.101
switching device
device designed to make or break the current in one or more electric circuits
[SOURCE: IEC 60050-441:2000, 441-14-01]

– 10 – IEC 62271-106:2021  IEC 2021
3.4.102
mechanical switching device
switching device (such as a contactor or a disconnector) designed to close and open one or
more electric circuits by means of separable contacts
[SOURCE: IEC 60050-441:2000, 441-14-02, modified: Note 1 to entry deleted.]
3.4.103
disconnector
mechanical switching device which provides, in the open position, an isolating distance in
accordance with specified requirements
Note 1 to entry: A disconnector is capable of opening and closing a circuit either when negligible current is broken
or made, or when no significant change in the voltage across the terminals of each of the poles of the disconnector
occurs. It is also capable of carrying currents under normal circuit conditions and carrying for a specified time currents
under abnormal conditions such as those of short circuit.
Note 2 to entry: A withdrawable contactor assembly may be used as a disconnector.
Note 3 to entry: In North America, this device is also called an isolating means or an isolating switch.
[SOURCE: IEC 60050-441:2000, 441-14-05, modified: Note 2 and 3 added.]
3.4.104
earthing switch
mechanical switching device for earthing parts of a circuit, capable of withstanding for a
specified time currents under abnormal conditions such as those of short circuit, but not
required to carry current under normal conditions of the circuit
Note 1 to entry: An earthing switch may have a short-circuit making capacity.
[SOURCE: IEC 60050-441:2000, 441-14-11]
3.4.105
contactor
mechanical switching device having only one position of rest, operated otherwise than by hand,
capable of making, carrying and breaking currents under normal circuit conditions including
operating overload conditions
Note 1 to entry: Contactors may be designated according to the method by which the force for closing the main
contacts is provided.
[SOURCE: IEC 60050-441:2000, 441-14-33]
3.4.106
electromagnetic contactor
contactor in which the force for closing or opening the main contacts is provided by an
electromagnet
3.4.107
vacuum contactor
contactor in which the main contacts open and close within a highly evacuated envelope
3.4.108
SF contactor
contactor in which the main contacts open and close within an SF gas-filled compartment
3.4.109
latched contactor
contactor, the moving elements of which are prevented by means of a latching arrangement
from returning to the position of rest when the operating means are de-energized
Note 1 to entry: The latching, and the release of the latching, may be mechanical, electromagnetic, pneumatic, etc.
[SOURCE: IEC 60050-441:2000, 441-14-34, modified: Note 2 to entry deleted.]
3.4.110
starter
combination of all the switching means necessary to start and stop a motor in combination with
suitable overload protection
[SOURCE: IEC 60050-441:2000, 441-14-38, modified: Note 1 to entry deleted.]
3.4.110.1
direct-on-line starter
starter which connects the line voltage across the motor terminals in one step
[SOURCE: IEC 60050-441:2000, 441-14-40]
3.4.110.2
reversing starter
starter intended to cause the motor to reverse the direction of rotation by reversing the motor
primary connections even when the motor is running
3.4.110.3
two-direction starter
starter intended to cause the motor to reverse the direction of rotation by reversing the motor
primary connections only when the motor is not running
3.4.110.4
reduced kVA starter
starter which reduces the starting kVA of the motor
Note 1 to entry: Reduced kVA starters may include auto-transformer, reactor, rheostatic starters.
3.4.110.5
auto-transformer starter
starter which uses one or more reduced voltages derived from an auto-transformer
3.4.110.6
rheostatic starter
starter utilizing one or several resistors for obtaining, during starting, stated motor torque
characteristics and for limiting the current
Note 1 to entry: A rheostatic starter generally consists of three basic parts, which may be supplied either as a
composite unit or as separate units to be connected at the place of utilization:
– the mechanical switching devices for supplying the stator (generally associated with an overload protective
device);
– the resistor(s) inserted in the rotor circuit;
– the mechanical switching devices for cutting out the resistor(s) successively.
[SOURCE: IEC 60050-441:2000, 441-14-42, modified: Note 1 to entry added.]

– 12 – IEC 62271-106:2021  IEC 2021
3.4.110.7
rheostatic rotor starter
rheostatic starter for an asynchronous wound-rotor motor which, during the starting period, cuts
out successively one or several resistors previously provided in the rotor circuit
[SOURCE: IEC 60050-441:2000, 441-14-43]
3.4.110.8
reactor starter
primary reactor starter
starter that includes a reactor connected in series with the stator winding of an alternating
current motor to furnish reduced voltage for starting
3.4.110.9
electromagnetic starter
starter in which the force for closing the main contacts is provided by an electromagnet
3.4.110.10
n-step starter
starter in which there are (n – 1) intermediate accelerating positions between the off and full on
positions
Note 1 to entry: A starter in which there is no intermediate accelerating position between the OFF and ON positions
is a single step or direct-on-line starter (see 3.4.110.1).
Note 2 to entry: A starter in which there is only one intermediate accelerating position between the OFF and ON
positions is known as a two-step starter.
Note 3 to entry: A three-step rheostatic starter has two sections of resistors used for starting.
[SOURCE: IEC 60050-441:2000, 441-14-41]
3.4.111
controller
combination starter
equipment consisting of a contactor, overload protection, a disconnector and a short-circuit
protective device (SCPD), mounted and wired in one common enclosure
Note 1 to entry: A controller may be used for functions other than motor starting, for example transformer control
and protection, or capacitor control.
3.4.111.1
transformer controller
combination of all the switching means necessary to energize and de-energize a transformer in
combination with suitable overload protection
3.4.111.2
capacitor controller
combination of all the switching means necessary to energize and de-energize a capacitor or
capacitor bank in combination with suitable protection
3.4.112
short-circuit protective device
SCPD
device intended to protect a circuit or parts of a circuit against short-circuit currents by
interrupting them
Note 1 to entry: Usually this function is provided by fuses.

3.4.113
contactor class C1
contactor with a low probability of restrike during capacitive current breaking as demonstrated
by the type tests
3.4.114
contactor class C2
contactor with a very low probability of restrike during capacitive current breaking as
demonstrated by type tests
3.5 Parts of switchgear and controlgear
Subclause 3.5 of 62271-1:2017 applies with the following modifications:
3.5.101 Parts of contactors, starters and controllers
3.5.101.1
pole of a switching device
portion of a switching device associated exclusively with one electrically separated conducting
path of its main circuit and excluding those portions which provide a means for mounting and
operating all poles together
Note 1 to entry: A switching device is called single-pole if it has only one pole. If it has more than one pole, it may
be called multipole (two-pole, three-pole, etc.) provided the poles are or can be coupled in such a manner as to
operate together.
[SOURCE: IEC 60050-441:2000, 441-15-01]
3.5.101.2
main circuit
all the conductive parts of a switching device included in the circuit which it is designed to close
or open
[SOURCE: IEC 60050-441:2000, 441-15-02]
3.5.101.3
control circuit
all the conductive parts (other than the main circuit) of a switching device which are included in
a circuit used for the closing operation or opening operation, or both, of the device
[SOURCE: IEC 60050-441:2000, 441-15-03]
3.5.101.4
auxiliary circuit
all the conductive parts of a switching device which are intended to be included in a circuit other
than the main circuit and the control circuits of the device
Note 1 to entry: Some auxiliary circuits fulfil supplementary functions such as signalling, interlocking, etc., and, as
such, they may be part of the control circuit of another switching device.
[SOURCE: IEC 60050-441:2000, 441-15-04]
3.5.101.5
main contact
contact included in the main circuit of a mechanical switching device, intended to carry, in the
closed position, the current of the main circuit
[SOURCE: IEC 60050-441:2000, 441-15-07]

– 14 – IEC 62271-106:2021  IEC 2021
3.5.101.6
control contact
contact included in a control circuit of a mechanical switching device and mechanically operated
by this device
[SOURCE: IEC 60050-441:2000, 441-15-09]
3.5.101.7
auxiliary contact
contact included in an auxiliary circuit and mechanically operated by the switching device
[SOURCE: IEC 60050-441:2000, 441-15-10]
3.5.101.8
"a" contact
make contact
control or auxiliary contact which is closed when the main contacts of the mechanical switching
device are closed and open when they are open
[SOURCE: IEC 60050-441:2000, 441-15-12]
3.5.101.9
"b" contact
break contact
control or auxiliary contact which is open when the main contacts of a mechanical switching
device are closed and closed when they are open
[SOURCE: IEC 60050-441:2000, 441-15-13]
3.5.110 Fuses
3.5.110.1
fuse
device that by the fusing of one or more of its specially designed and proportioned components
opens the circuit in which it is inserted by breaking the current when this exceeds a given value
for a sufficient time. The fuse comprises all the parts that form the complete device
Note 1 to entry: Fuses are commonly used as the SCPD in starts and controllers (3.4.112).
[SOURCE: IEC 60050-441:2000, 441-18-01]
3.5.110.2
striker
mechanical device forming part of a fuse-link which, when the fuse operates, releases the
energy required to cause operation of other apparatus or indicators, or to provide interlocking
[SOURCE: IEC 60050-441:2000, 441-18-18]
3.5.110.3
pre-arcing time
melting time
interval of time between the beginning of a current large enough to cause a break in the fuse-
element(s) and the instant when an arc is initiated
[SOURCE: IEC 60050-441:2000, 441-18-21]

3.5.110.4
operating time
total clearing time
sum of the pre-arcing time and the arcing time
[SOURCE: IEC 60050-441:2000, 441-18-22]
3.5.110.5
Joule integral
I t
integral of the square of the current over a given time interval:
t
2 2
I t = i d t
∫
t
2 2
Note 1 to entry: The pre-arcing I t is the I t integral extended over the pre-arcing time of the fuse.
2 2
Note 2 to entry: The operating I t is the I t integral extended over the operating time of the fuse.
Note 3 to entry: The energy in joules liberated in one ohm of resistance in a circuit protected by a fuse is equal to
2 2
the value of the operating I t expressed in A s.
[SOURCE: IEC 60050-441:2000, 441-18-23]
3.5.112
extendable power bus
main power bus
that portion of the power bus that is capable of being extended to connect two or more vertical
sections or controllers
3.6 Operational characteristics of switchgear and controlgear
Subclause 3.6 of IEC 62271-1: 2017 applies with the following modifications:
3.6.101
operation
transfer of the moving contact(s) from one position to an adjacent position
Note 1 to entry: For a circuit-breaker, this can be a closing operation or an opening operation.
Note 2 to entry: If distinction is necessary, an operation in the electrical sense, e.g. make or break, is referred to
as a switching operation, and an operation in the mechanical sense, e.g. close or open, is referred to as a mechanical
operation.
[SOURCE: IEC 60050-441:2000, 441-16-01]
3.6.102
operating cycle
succession of operations from one position to another and back to the first position through all
other positions, if any
Note 1 to entry: This may be a closing operation followed by an opening operation.
Note 2 to entry: A succession of operations not forming an operating cycle is referred to as an operating series.
[SOURCE: IEC 60050-441:2000, 441-16-02, modified: Notes 1 and 2 added.]
3.6.103
closing operation
operation by which the device is brought from the open position to the closed position

– 16 – IEC 62271-106:2021  IEC 2021
[SOURCE: IEC 60050-441:2000, 441-16-08]
3.6.104
opening operation
operation by which the device is brought from the closed position to the open position
[SOURCE: IEC 60050-441:2000, 441-16-09]
3.6.105
closed position
position in which the predetermined continuity of the main circuit of the device is secured
[SOURCE: IEC 60050-441:2000, 441-16-22]
3.6.106
open position
position in which the predetermined clearance between open contacts in the main circuit of the
device is secured
[SOURCE: IEC 60050-441:2000, 441-16-23]
3.6.107
position of rest
position which the moving elements of the contactor take up when its electromagnet or its
compressed-air device is not energized
[SOURCE: IEC 60050-441:2000, 441-16-24]
3.6.108
overload relay or release
over-current relay or release intended for protection against overloads (including, where
applicable, operating transformer(s) and interconnections)
3.6.109
thermal overload relay or release
inverse time-delay overload relay or release depending for its operation (including its time
delay) on the thermal action of the current flowing in the relay or release
3.6.110
current setting of an overload relay or release
value of current for which the relay or release is adjusted and in accordance with which its
operating conditions are defined
3.6.111
current setting range of an overload relay or release
range between the minimum and maximum values over which the current setting of the relay or
release can be adjusted
3.6.112
phase failure sensitive overload relay or release
multi-pole overload relay or release which, in accordance with specified requirements, operates
at a current value lower than its current setting in the case of current unbalance
3.6.113
under-current (under-voltage) relay or release
measuring relay or release which operates automatically when the current through it (or the
voltage applied to it) is reduced below a pre-determined value

3.6.114
starting time
period of time during which the starting resistors or parts of them carry current
Note 1 to entry: The starting time of a starter is shorter than the total starting time of the motor, which takes into
account the last period of acceleration following the switching operation ON position.
3.6.115
starting time
period of time during which the auto-transformer carries current
Note 1 to entry: The starting time of a starter is shorter than the total starting time of the motor, which takes into
account the last period of acceleration following the switching operation ON position.
3.6.116
open transition
circuit arrangement so that the supply to the motor is interrupted and reconnected when
changing over from one step to another
Note 1 to entry: The transition stage is not considered an additional step.
3.6.117
closed transition
circuit arrangement so that the supply to the motor is not interrupted (even momentarily) when
changing over from one step to another
Note 1 to entry: The transition stage is not considered an additional step.
3.6.118
inching
jogging
energizing a motor or solenoid repeatedly for short periods to obtain small movements of the
driven mechanism
3.6.119
plugging
stopping or reversing a motor rapidly by reversing the motor primary connections while the
motor is running
3.7 Characteristic quantities
Subclause 3.7 of 62271-1: 2017 applies with the following additions:
3.7.101
breaking current
current in a pole of a switching device or in a fuse at the instant of initiation of the arc during a
breaking process
[SOURCE: IEC 60050-441:2000, 441-17-07]
3.7.102
breaking capacity
value of prospective current that a switching device or a fuse is capable of breaking at a stated
voltage under prescribed conditions of use and behaviour
Note 1 to entry: The voltage to be stated and the conditions to be prescribed are dealt with in the relevant
publications.
Note 2 to entry: For switching devices, the breaking capacity may be termed according to the kind of current
included in the prescribed conditions, e.g. line charging breaking capacity, cable charging breaking capacity, single
capacitor bank breaking capacity, etc.

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