IEC 60034-11:2020
(Main)Rotating electrical machines - Part 11: Thermal protection
Rotating electrical machines - Part 11: Thermal protection
IEC 60034-11:2020 specifies requirements relating to the use of thermal protectors and thermal detectors incorporated into the stator windings or placed in other suitable positions in induction machines in order to protect them against serious damage due to thermal overloads. It applies to single-speed three-phase 50 Hz or 60 Hz cage induction motors in accordance with IEC 60034-1 and IEC 60034-12 that:
- have a rated voltage up to 1 000 V;
- are intended for direct-on-line or star-delta starting.
The main changes with respect to the previous edition are:
- the additional specification of winding temperature limits for temperature class 200 (N),
- the increased limits of maximum winding temperatures for overloads with rapid variation,
- the clarification that the motor winding may be permanently damaged after it has been exposed to temperatures
- a clarification of the definition of indirect thermal protection,
- a clarification on the test methods for larger motors.
Machines électriques tournantes - Partie 11: Protection thermique
L'IEC 60034-11:2020 spécifie les exigences relatives à l’utilisation de protecteurs et détecteurs thermiques incorporés dans les enroulements statoriques, ou autres emplacements adaptés, dans les machines à induction afin de les protéger contre de graves dommages dus aux surcharges thermiques. Elle s’applique aux moteurs triphasés à induction à cage à une seule vitesse fonctionnant à 50 Hz ou 60 Hz conformément à l’IEC 60034-1 et à l’IEC 60034-12 qui:
- ont une tension assignée jusqu’à 1 000 V;
- sont prévus pour un démarrage direct ou étoile-triangle.
Par rapport à l’édition précédente, les modifications majeures sont les suivantes
- spécification supplémentaire relative aux limites de température de l’enroulement pour la classe thermique 200 (N),
- augmentation des limites des températures maximales d’enroulement pour surcharges à évolution rapide,
- précision concernant l’enroulement du moteur qui peut être endommagé de façon permanente après une exposition aux températures,
- précision de la définition de protection thermique indirecte,
- précision, au 8.3, concernant les méthodes d’essai pour les moteurs plus importants.
General Information
Relations
Overview
IEC 60034-11:2020 - "Rotating electrical machines - Part 11: Thermal protection" specifies requirements for the selection, placement and performance of thermal protectors and thermal detectors used to protect stator windings (or other suitable positions) of cage induction motors against serious thermal damage. The standard applies to single‑speed, three‑phase, 50 Hz or 60 Hz cage induction motors (direct-on-line or star‑delta starting) manufactured in accordance with IEC 60034‑1 and IEC 60034‑12, with rated voltages up to 1 000 V.
Key topics and technical requirements
- Scope and limits
- Applies to stator winding protection; does not include direct rotor winding protection, bearings or other mechanical parts.
- Intended for motors that are DOL or star‑delta started and up to 1 000 V rated voltage.
- Thermal protection types
- Defines thermal protector (direct switching device) and thermal detector (temperature‑sensing device initiating a protection function).
- Clarifies direct vs indirect thermal protection (e.g., stator sensor protecting rotor indirectly).
- Temperature limits
- Specifies maximum allowable winding temperatures for overloads with slow variation (Table 1). Example temperature limits by thermal class:
- Class 130 (B) → 145 °C
- Class 155 (F) → 170 °C
- Class 180 (H) → 195 °C
- Class 200 (N) → 215 °C
- Defines limits for overloads with rapid variation (Table 2); the 2020 edition increases those limits and clarifies that exposure to those temperatures may cause permanent winding damage.
- Specifies maximum allowable winding temperatures for overloads with slow variation (Table 1). Example temperature limits by thermal class:
- Measurement and testing
- Winding temperature shall be determined by the resistance method per IEC 60034‑1 (clause 8.6.2).
- Details type tests and routine tests to verify protection under slow and rapid thermal transients (Clauses 8.2, 8.3).
- Operational guidance
- Machines must operate at rated output without nuisance tripping; protection must prevent exceedance of specified temperature limits.
- The standard balances avoiding nuisance trips and preventing accelerated insulation ageing.
Practical applications and users
IEC 60034‑11 is essential for:
- Motor manufacturers and designers selecting and integrating thermal protection systems.
- OEMs and panel builders specifying motor protection for industrial equipment.
- Test laboratories and certification bodies performing type and routine thermal tests.
- Maintenance engineers and asset managers defining protection/upkeep policies to avoid thermal overload and premature insulation failure.
- Specifiers writing procurement requirements for induction motors in industrial, HVAC, pump and conveyor applications.
Related standards
- IEC 60034‑1: Rotating electrical machines - Rating and performance (temperature measurement methods referenced).
- IEC 60034‑12: Starting performance of single‑speed three‑phase cage induction motors.
Keywords: IEC 60034-11:2020, thermal protection, rotating electrical machines, stator winding, thermal detectors, thermal protectors, induction motors, winding temperature limits, direct thermal protection, indirect thermal protection.
Standards Content (Sample)
IEC 60034-11 ®
Edition 3.0 2020-10
REDLINE VERSION
INTERNATIONAL
STANDARD
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inside
Rotating electrical machines –
Part 11: Thermal protection
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IEC 60034-11 ®
Edition 3.0 2020-10
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Rotating electrical machines –
Part 11: Thermal protection
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.160.01 ISBN 978-2-8322-8936-5
– 2 – IEC 60034-11:2020 RLV © IEC 2020
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Thermal protection limits . 7
5 Protection against thermal overloads with slow variation . 8
6 Protection against thermal overloads with rapid variation . 10
7 Restart after tripping . 12
8 Type tests . 13
8.1 General . 13
8.2 Verification of temperature due to the thermal overloads with slow variation . 13
8.3 Verification of temperature due to thermal overloads with rapid variation . 13
9 Routine tests . 13
Figure 1 – Example of thermal overload with slow variation and direct thermal
protection . 9
Figure 2 – Example of thermal overload with slow variation in the case of too intensive
intermittent periodic duty with starting (duty S4) and direct thermal protection . 9
Figure 3 – Example of thermal overload with rapid variation where the thermally critical
part has direct thermal protection . 11
Figure 4 – Example of thermal overload with rapid variation where the thermally critical
part has indirect thermal protection . 12
Table 1 – Maximum winding temperatures for overloads with slow variation . 8
Table 2 – Maximum winding temperatures for overloads with rapid variation . 10
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ROTATING ELECTRICAL MACHINES –
Part 11: Thermal protection
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) 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.
This redline version of the official IEC Standard allows the user to identify the changes
made to the previous edition. 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 60034-11:2020 RLV © IEC 2020
International Standard IEC 60034-11 has been prepared by IEC technical committee 2: Rotating
machinery.
This third edition cancels and replaces the second edition, published in 2004. This edition
constitutes a technical revision.
The main changes with respect to the previous edition are
– the additional specification of winding temperature limits for temperature class 200 (N),
– the increased limits of maximum winding temperatures for overloads with rapid variation,
– the clarification that the motor winding may be permanently damaged after it has been
exposed to temperatures according to Table 2,
– a clarification of scope,
– a clarification of the definition of indirect thermal protection,
– a clarifying note in Clause 6,
– the conversion of note 3 in Clause 6 into normal text including changes in wording,
– the incorporation of note 3 in Clause 5 into Clause 2,
– a clarification on the test methods for larger motors in 8.3.
The text of this International Standard is based on the following documents:
FDIS Report on voting
2/2011/FDIS 2/2019/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.
A list of all parts in the IEC 60034 series, published under the general title Rotating electrical
machines, 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.
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.
INTRODUCTION
Thermal protection systems are based on the principle of protecting or monitoring the vulnerable
machine parts against excessive temperatures. This requires the selection of the appropriate
thermal protection device to suit both the type of protection required and the machine
component to be protected. This document does not detail the protection methods available or
specify the protection method to be used for particular applications, but instead it specifies the
temperature of the protected parts that should not be exceeded if a fault or machine abuse
occurs.
The requirements are not intended to guarantee a "normal" machine life for all conditions of
use, but rather to avoid both failure and accelerated premature thermal ageing of the winding
insulation. The requirements result from a compromise, since the level of protection should
neither be set so low that it causes nuisance tripping nor so high that it allows continuous
working at temperatures that will seriously affect the life of the winding insulation.
Normal insulation life can only be ensured by correct motor application and maintenance.
Frequent operation at above the normal temperature limits, see IEC 60034-1, which cannot be
prevented by built-in thermal protection without risking nuisance tripping may lead to a
noticeable reduction in machine life. It should be noted that The life of the winding insulation
is approximately halved for every 8 K to 10 K increase in the continuous operating temperature.
The requirement to incorporate thermal protection in a machine is a matter for agreement. The
application of this document should be is a matter of agreement between the user and the
machine manufacturer.
– 6 – IEC 60034-11:2020 RLV © IEC 2020
ROTATING ELECTRICAL MACHINES –
Part 11: Thermal protection
1 Scope
This part of IEC 60034 specifies requirements relating to the use of thermal protectors and
thermal detectors incorporated into the stator windings or placed in other suitable positions in
induction machines in order to protect them against serious damage due to thermal overloads.
It applies to machines manufactured in accordance with IEC 60034-12 with the voltage limits
specified in IEC 60034-12. The protection of bearings and other mechanical parts is not
included. It applies to single-speed three-phase 50 Hz or 60 Hz cage induction motors in
accordance with IEC 60034-1 and IEC 60034-12 that:
• have a rated voltage up to 1 000 V;
• are intended for direct-on-line or star-delta starting.
Not included are:
• direct protection of the rotor winding; the methods of protection only protect rotor windings
indirectly; for large motors (particularly 2 pole motors) and for motors starting large inertia
loads, special attention is given to rotor heating both when starting and especially after a
"trip" has occurred;
• the protection of bearings and other mechanical parts;
• the protection methods to be used for particular applications.
NOTE 1 Although temperature values given in this document are higher than those specified in IEC 60034-1, they
are not in conflict.
NOTE 2 Additional requirements may apply to particular motor types, such as those used in household appliances,
or for motors used in explosive atmospheres.
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 60034-1:20042017, Rotating electrical machines – Part 1: Rating and performance
IEC 60034-12:20022016, Rotating electrical machines – Part 12: Starting performance of
single-speed three-phase cage induction motors
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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
thermal protection
protection of windings of a machine against excessive temperature resulting from conditions of
overload or loss of cooling
3.2
thermal protection system
system for the protection of a machine winding against excessive temperature resulting from
conditions of overload or loss of cooling by means of either thermal protector(s) or thermal
detector(s)
3.3
thermal detector
electrically insulated device that is only sensitive to temperature, capable of initiating a
switching function in a protection system when its temperature reaches a predetermined level
3.4
thermal protector
electrically insulated device that is sensitive to the temperature of the machine winding which
carries machine current, capable of directly switching off the machine when its temperature
reaches a predetermined level
Note 1 to entry: Some thermal protectors are sensitive to both temperature and current, the combination of which
activates the direct switching off of the machine.
3.5
thermal overload with slow variation
overload condition or loss of cooling that produces a rise of temperature that is sufficiently slow
that the temperature of the thermal protector or detector follows it without appreciable delay
3.6
thermal overload with rapid variation
overload condition or loss of cooling that produces a rise of temperature that is too rapid for the
temperature of the thermal protector or detector to follow without appreciable delay resulting in
a significant temperature difference between the thermal device and the part to be protected
3.7
maximum temperature after tripping
maximum value of the temperature that is reached by the protected part of the machine during
the period which follows tripping by the thermal protection system
3.8
direct thermal protection
form of protection where the part of the machine in which the thermal detector(s) or thermal
protector(s) are incorporated is the part for which protection is being provided
3.9
indirect thermal protection
form of protection where the part of the machine in which the thermal detector(s) or thermal
protector(s) are incorporated (e.g. the stator winding) is not the part for which protection is
being provided (e.g. the rotor winding)
4 Thermal protection limits
Machines shall be capable of operating at rated output and at all operating conditions according
to IEC 60034-1 without activation of the thermal protection device. The thermal protection
device shall limit the winding temperature in accordance with Clause 5 or Clause 6.
– 8 – IEC 60034-11:2020 RLV © IEC 2020
5 Protection against thermal overloads with slow variation
When subjected to an overload or other misuse condition causing overheating with slow
variation, the protection system shall operate to prevent the temperature of the machine winding
from exceeding the values in Table 1.
Examples of the rise in temperature as a function of time are shown in Figure 1 and Figure 2.
Table 1 – Maximum winding temperatures for overloads with slow variation
Thermal class 130(B) 155(F) 180(H) 200(N)
145 170 195 215
Maximum insulated winding temperature °C
The winding temperature shall be determined by the resistance method in accordance with the
requirements of 8.6.2 of IEC 60034-1:2017.
NOTE 1 The limit values in Table 1 exceed the thermal classification and thus will reduce the lifetime of the motor,
if the motor is operated over a longer period of time with these values.
NOTE 2 The maximum temperature limits are based on experience. Some of the ways in which a thermal overload
with slow variation may be caused are:
• Defects in ventilation or the ventilation system due to excessive dust in the ventilation ducts, or dirt on windings
or frame cooling ribs, etc.
• An excessive rise in ambient temperature or the temperature of the cooling medium.
• Gradual increasing mechanical overload.
• Prolonged voltage drop, over-voltage or unbalance in the machine supply.
• Excessive duty on a motor rated for intermittent duty.
• Frequency deviations.
NOTE 3 The maximum temperature limits are based on experience taking into account factors such as ambient
temperature, variations in supply voltage and normal requirements for starting motors.
Key
1 is the winding temperature in the vicinity of the thermal protector or detector
2 is the temperature of the thermal protector or detector
3 is the temperature when operating at normal duty
4 is the time at the beginning of the thermal overload
X axis is time
Y axis is temperature
Figure 1 – Example of thermal overload with slow variation
and direct thermal protection
Key
1 is the winding temperature in the vicinity of the thermal detector or protector
2 is the temperature of the thermal detector or protector
3 is the interval with normal cycling frequency
4 is the time at the beginning of the thermal overload
X axis is time
Y axis is temperature
Figure 2 – Example of thermal overload with slow variation in the case of too intensive
intermittent periodic duty with starting (duty S4) and direct thermal protection
– 10 – IEC 60034-11:2020 RLV © IEC 2020
6 Protection against thermal overloads with rapid variation
When a thermal overload with rapid variation is applied to the machine, the thermal protection
system shall operate to prevent the temperature of the machine winding from exceeding the
values given in Table 2.
A current overload relay does not normally provide protection against repeated rapid overload
variations and the use of a thermal protection device should be considered
Examples of the rise in temperature as a function of time are shown in Figure 3 and Figure 4.
Table 2 – Maximum winding temperatures for overloads with rapid variation
Thermal class 130(B) 155(F) 180(H) 200(N)
225 240 250 260 275 295
Maximum insulated winding temperature °C
The winding temperature shall be determined by direct measurements such as thermocouples
in accordance with the requirements of 8.5.3 of IEC 60034-1:2017.
It is understood that the motor winding may be permanently damaged and may not be able to
operate after it has been exposed to temperatures according to Table 2.
NOTE 1 Some of the ways in which a thermal overload with rapid variation may be caused are:
• Stalling the motor.
• Phase failure.
• Starting under abnormal conditions, for example, inertia too great, voltage too low, load torque abnormally high;
• Sudden and significant increase in load.
• Starting repeatedly during a short time.
NOTE 2 The maximum temperature limits are based on experience, taking into account factors such as ambient
temperature, variations in supply voltage and normal requirements for starting motors.
NOTE 3 The temperatures in Table 2 should shall not be confused with the operating
temperatures of the winding’s thermal protector or thermal detector operating temperatures
which have to be significantly below these values. The thermal protector shall be installed at a
place where the highest temperatures are expected according to the application and the motor
cooling system.
Key
1 is the maximum winding temperature after tripping
2 is the winding temperature in the vicinity of the thermal protector or detector
3 is the temperature when operating at normal duty
4 is the time at the beginning of the thermal overload
5 is the time at which tripping occurs
6 is the temperature of the thermal protector or detector
7 is the operating temperature of the thermal detector or protector
X axis is time
Y axis is temperature
Figure 3 – Example of thermal overload with rapid variation
where the thermally critical part has direct thermal protection
– 12 – IEC 60034-11:2020 RLV © IEC 2020
Key
1 is the maximum temperature after tripping
2 is temperature of the part which is the thermally critical part for a thermal overload with rapid variation
3 is the temperature when operating at normal duty
4 is the beginning of thermal overload with rapid variation
5 is the tripping time
6 is the temperature of the thermal detector or protector incorporated in the thermally critical part for thermal
overload with slow variation
7 is the temperature of the part which is not the thermally critical part of the thermal overload with rapid variation,
but which is the thermally critical part for a thermal overload with slow variation
X axis is time
Y axis is temperature
Figure 4 – Example of thermal overload with rapid variation
where the thermally critical part has indirect thermal protection
7 Restart after tripping
Before restarting a machine that has tripped, an investigation shall be made to try to identify
the cause of the operation of the machine protection. When attempting to restart the machine,
account shall be taken of the conditions stated in 6.3 or 89.3 of IEC 60034-12:2016.
The methods of protection included in this document only protect rotor windings indirectly. For
large motors (particularly 2 pole motors) and for motors starting large inertia loads, special
attention needs to be given to rotor heating both when starting and especially after a "trip" has
occurred.
NOTE The provision of the facility to enable machines to be automatically restarted after tripping is a matter for
special agreement taking full account of all safety implications.
8 Type tests
8.1 General
Type tests are to verify the compliance of a thermal protection system with the requirements of
this document.
Tests shall be made on a machine which is representative of the machine type. The proposed
thermal protection system shall be installed.
Temperature sensors used for testing shall be located in positions representative of the location
of the thermal detectors used by the thermal protection system.
8.2 Verification of temperature due to the thermal overloads with slow variation
Starting with the machine at operating temperature, the load shall be slowly increased so that
the temperature of the winding increases at a rate of less than 1 K per 5 min. Temperatures
shall be recorded at a minimum of 10 min intervals.
When the thermal protection system trips, the supply to the machine shall be switched off if it is
not directly interrupted by the thermal protection device. The winding temperature shall be
determined immediately after tripping in accordance with the requirements of 8.6.2 of
IEC 60034-1:2017.
The winding temperatures specified in Table 1 shall not be exceeded.
8.3 Verification of temperature due to thermal overloads with rapid variation
Verification of the temperature is required only in cases where a motor is protected by built-in
positive temperature coefficient thermistors (PTC) or via a thermostat and where it is not
protected by a thermal protection device.
Starting with the machine at ambient temperature, with the rotor locked to prevent rotation,
apply rated voltage to the windings.
At the end of the energised period, the maximum temperature of the winding shall be recorded.
For manual re-set systems, the protector shall be re-closed as quickly as possible and power
restored.
Protection systems with automatic resetting shall be operated for a minimum of 10 cycles,
unless the change in peak temperature between two cycles is below 5 K.
The highest temperature attained shall not exceed the values in Table 2.
9 Routine tests
Devices used for thermal detection shall be tested for circuit continuity to assure that no damage
has occurred during installation.
____________
IEC 60034-11 ®
Edition 3.0 2020-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Rotating electrical machines –
Part 11: Thermal protection
Machines électriques tournantes –
Partie 11: Protection thermique
– 2 – IEC 60034-11:2020 © IEC 2020
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Thermal protection limits . 7
5 Protection against thermal overloads with slow variation . 8
6 Protection against thermal overloads with rapid variation . 9
7 Restart after tripping . 11
8 Type tests . 12
8.1 General . 12
8.2 Verification of temperature due to the thermal overloads with slow variation . 12
8.3 Verification of temperature due to thermal overloads with rapid variation . 12
9 Routine tests . 12
Figure 1 – Example of thermal overload with slow variation and direct thermal
protection . 8
Figure 2 – Example of thermal overload with slow variation in the case of too intensive
intermittent periodic duty with starting (duty S4) and direct thermal protection . 9
Figure 3 – Example of thermal overload with rapid variation where the thermally critical
part has direct thermal protection . 10
Figure 4 – Example of thermal overload with rapid variation where the thermally critical
part has indirect thermal protection . 11
Table 1 – Maximum winding temperatures for overloads with slow variation . 8
Table 2 – Maximum winding temperatures for overloads with rapid variation . 9
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ROTATING ELECTRICAL MACHINES –
Part 11: Thermal protection
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) 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 60034-11 has been prepared by IEC technical committee 2: Rotating
machinery.
This third edition cancels and replaces the second edition, published in 2004. This edition
constitutes a technical revision.
The main changes with respect to the previous edition are
– the additional specification of winding temperature limits for temperature class 200 (N),
– the increased limits of maximum winding temperatures for overloads with rapid variation,
– the clarification that the motor winding may be permanently damaged after it has been
exposed to temperatures according to Table 2,
– a clarification of scope,
– a clarification of the definition of indirect thermal protection,
– a clarifying note in Clause 6,
– the conversion of note 3 in Clause 6 into normal text including changes in wording,
– 4 – IEC 60034-11:2020 © IEC 2020
– the incorporation of note 3 in Clause 5 into Clause 2,
– a clarification on the test methods for larger motors in 8.3.
The text of this International Standard is based on the following documents:
FDIS Report on voting
2/2011/FDIS 2/2019/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.
A list of all parts in the IEC 60034 series, published under the general title Rotating electrical
machines, 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.
INTRODUCTION
Thermal protection systems are based on the principle of protecting or monitoring the vulnerable
machine parts against excessive temperatures. This requires the selection of the appropriate
thermal protection device to suit both the type of protection required and the machine
component to be protected. This document does not detail the protection methods available or
specify the protection method to be used for particular applications, but instead it specifies the
temperature of the protected parts that should not be exceeded if a fault or machine abuse
occurs.
The requirements are not intended to guarantee a "normal" machine life for all conditions of
use, but rather to avoid both failure and accelerated premature thermal ageing of the winding
insulation. The requirements result from a compromise, since the level of protection should
neither be set so low that it causes nuisance tripping nor so high that it allows continuous
working at temperatures that will seriously affect the life of the winding insulation.
Normal insulation life can only be ensured by correct motor application and maintenance.
Frequent operation at above the normal temperature limits, see IEC 60034-1, which cannot be
prevented by built-in thermal protection without risking nuisance tripping may lead to a
noticeable reduction in machine life. The life of the winding insulation is approximately halved
for every 8 K to 10 K increase in the continuous operating temperature.
The requirement to incorporate thermal protection in a machine is a matter for agreement. The
application of this document is a matter of agreement between the user and the machine
manufacturer.
– 6 – IEC 60034-11:2020 © IEC 2020
ROTATING ELECTRICAL MACHINES –
Part 11: Thermal protection
1 Scope
This part of IEC 60034 specifies requirements relating to the use of thermal protectors and
thermal detectors incorporated into the stator windings or placed in other suitable positions in
induction machines in order to protect them against serious damage due to thermal overloads.
It applies to single-speed three-phase 50 Hz or 60 Hz cage induction motors in accordance with
IEC 60034-1 and IEC 60034-12 that:
• have a rated voltage up to 1 000 V;
• are intended for direct-on-line or star-delta starting.
Not included are:
• direct protection of the rotor winding; the methods of protection only protect rotor windings
indirectly; for large motors (particularly 2 pole motors) and for motors starting large inertia
loads, special attention is given to rotor heating both when starting and especially after a
"trip" has occurred;
• the protection of bearings and other mechanical parts;
• the protection methods to be used for particular applications.
NOTE 1 Although temperature values given in this document are higher than those specified in IEC 60034-1, they
are not in conflict.
NOTE 2 Additional requirements may apply to particular motor types, such as those used in household appliances,
or for motors used in explosive atmospheres.
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 60034-12:2016, Rotating electrical machines – Part 12: Starting performance of single-
speed three-phase cage induction motors
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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
thermal protection
protection of windings of a machine against excessive temperature resulting from conditions of
overload or loss of cooling
3.2
thermal protection system
system for the protection of a machine winding against excessive temperature resulting from
conditions of overload or loss of cooling by means of either thermal protector(s) or thermal
detector(s)
3.3
thermal detector
electrically insulated device that is only sensitive to temperature, capable of initiating a
switching function in a protection system when its temperature reaches a predetermined level
3.4
thermal protector
electrically insulated device that is sensitive to the temperature of the machine winding which
carries machine current, capable of directly switching off the machine when its temperature
reaches a predetermined level
Note 1 to entry: Some thermal protectors are sensitive to both temperature and current, the combination of which
activates the direct switching off of the machine.
3.5
thermal overload with slow variation
overload condition or loss of cooling that produces a rise of temperature that is sufficiently slow
that the temperature of the thermal protector or detector follows it without appreciable delay
3.6
thermal overload with rapid variation
overload condition or loss of cooling that produces a rise of temperature that is too rapid for the
temperature of the thermal protector or detector to follow without appreciable delay resulting in
a significant temperature difference between the thermal device and the part to be protected
3.7
maximum temperature after tripping
maximum value of the temperature that is reached by the protected part of the machine during
the period which follows tripping by the thermal protection system
3.8
direct thermal protection
form of protection where the part of the machine in which the thermal detector(s) or thermal
protector(s) are incorporated is the part for which protection is being provided
3.9
indirect thermal protection
form of protection where the part of the machine in which the thermal detector(s) or thermal
protector(s) are incorporated (e.g. the stator winding) is not the part for which protection is
being provided (e.g. the rotor winding)
4 Thermal protection limits
Machines shall be capable of operating at rated output and at all operating conditions according
to IEC 60034-1 without activation of the thermal protection device. The thermal protection
device shall limit the winding temperature in accordance with Clause 5 or Clause 6.
– 8 – IEC 60034-11:2020 © IEC 2020
5 Protection against thermal overloads with slow variation
When subjected to an overload or other misuse condition causing overheating with slow
variation, the protection system shall operate to prevent the temperature of the machine winding
from exceeding the values in Table 1.
Examples of the rise in temperature as a function of time are shown in Figure 1 and Figure 2.
Table 1 – Maximum winding temperatures for overloads with slow variation
Thermal class 130(B) 155(F) 180(H) 200(N)
145 170 195 215
Maximum insulated winding temperature °C
The winding temperature shall be determined by the resistance method in accordance with the
requirements of 8.6.2 of IEC 60034-1:2017.
NOTE 1 The limit values in Table 1 exceed the thermal classification and thus will reduce the lifetime of the motor.
NOTE 2 The maximum temperature limits are based on experience. Some of the ways in which a thermal overload
with slow variation may be caused are:
• Defects in ventilation or the ventilation system due to excessive dust in t
...
IEC 60034-11 ®
Edition 3.0 2020-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Rotating electrical machines –
Part 11: Thermal protection
Machines électriques tournantes –
Partie 11: Protection thermique
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IEC 60034-11 ®
Edition 3.0 2020-10
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Rotating electrical machines –
Part 11: Thermal protection
Machines électriques tournantes –
Partie 11: Protection thermique
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.160.01 ISBN 978-2-8322-8844-3
– 2 – IEC 60034-11:2020 © IEC 2020
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Thermal protection limits . 7
5 Protection against thermal overloads with slow variation . 8
6 Protection against thermal overloads with rapid variation . 9
7 Restart after tripping . 11
8 Type tests . 12
8.1 General . 12
8.2 Verification of temperature due to the thermal overloads with slow variation . 12
8.3 Verification of temperature due to thermal overloads with rapid variation . 12
9 Routine tests . 12
Figure 1 – Example of thermal overload with slow variation and direct thermal
protection . 8
Figure 2 – Example of thermal overload with slow variation in the case of too intensive
intermittent periodic duty with starting (duty S4) and direct thermal protection . 9
Figure 3 – Example of thermal overload with rapid variation where the thermally critical
part has direct thermal protection . 10
Figure 4 – Example of thermal overload with rapid variation where the thermally critical
part has indirect thermal protection . 11
Table 1 – Maximum winding temperatures for overloads with slow variation . 8
Table 2 – Maximum winding temperatures for overloads with rapid variation . 9
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ROTATING ELECTRICAL MACHINES –
Part 11: Thermal protection
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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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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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
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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 60034-11 has been prepared by IEC technical committee 2: Rotating
machinery.
This third edition cancels and replaces the second edition, published in 2004. This edition
constitutes a technical revision.
The main changes with respect to the previous edition are
– the additional specification of winding temperature limits for temperature class 200 (N),
– the increased limits of maximum winding temperatures for overloads with rapid variation,
– the clarification that the motor winding may be permanently damaged after it has been
exposed to temperatures according to Table 2,
– a clarification of scope,
– a clarification of the definition of indirect thermal protection,
– a clarifying note in Clause 6,
– the conversion of note 3 in Clause 6 into normal text including changes in wording,
– 4 – IEC 60034-11:2020 © IEC 2020
– the incorporation of note 3 in Clause 5 into Clause 2,
– a clarification on the test methods for larger motors in 8.3.
The text of this International Standard is based on the following documents:
FDIS Report on voting
2/2011/FDIS 2/2019/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.
A list of all parts in the IEC 60034 series, published under the general title Rotating electrical
machines, 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.
INTRODUCTION
Thermal protection systems are based on the principle of protecting or monitoring the vulnerable
machine parts against excessive temperatures. This requires the selection of the appropriate
thermal protection device to suit both the type of protection required and the machine
component to be protected. This document does not detail the protection methods available or
specify the protection method to be used for particular applications, but instead it specifies the
temperature of the protected parts that should not be exceeded if a fault or machine abuse
occurs.
The requirements are not intended to guarantee a "normal" machine life for all conditions of
use, but rather to avoid both failure and accelerated premature thermal ageing of the winding
insulation. The requirements result from a compromise, since the level of protection should
neither be set so low that it causes nuisance tripping nor so high that it allows continuous
working at temperatures that will seriously affect the life of the winding insulation.
Normal insulation life can only be ensured by correct motor application and maintenance.
Frequent operation at above the normal temperature limits, see IEC 60034-1, which cannot be
prevented by built-in thermal protection without risking nuisance tripping may lead to a
noticeable reduction in machine life. The life of the winding insulation is approximately halved
for every 8 K to 10 K increase in the continuous operating temperature.
The requirement to incorporate thermal protection in a machine is a matter for agreement. The
application of this document is a matter of agreement between the user and the machine
manufacturer.
– 6 – IEC 60034-11:2020 © IEC 2020
ROTATING ELECTRICAL MACHINES –
Part 11: Thermal protection
1 Scope
This part of IEC 60034 specifies requirements relating to the use of thermal protectors and
thermal detectors incorporated into the stator windings or placed in other suitable positions in
induction machines in order to protect them against serious damage due to thermal overloads.
It applies to single-speed three-phase 50 Hz or 60 Hz cage induction motors in accordance with
IEC 60034-1 and IEC 60034-12 that:
• have a rated voltage up to 1 000 V;
• are intended for direct-on-line or star-delta starting.
Not included are:
• direct protection of the rotor winding; the methods of protection only protect rotor windings
indirectly; for large motors (particularly 2 pole motors) and for motors starting large inertia
loads, special attention is given to rotor heating both when starting and especially after a
"trip" has occurred;
• the protection of bearings and other mechanical parts;
• the protection methods to be used for particular applications.
NOTE 1 Although temperature values given in this document are higher than those specified in IEC 60034-1, they
are not in conflict.
NOTE 2 Additional requirements may apply to particular motor types, such as those used in household appliances,
or for motors used in explosive atmospheres.
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 60034-12:2016, Rotating electrical machines – Part 12: Starting performance of single-
speed three-phase cage induction motors
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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
thermal protection
protection of windings of a machine against excessive temperature resulting from conditions of
overload or loss of cooling
3.2
thermal protection system
system for the protection of a machine winding against excessive temperature resulting from
conditions of overload or loss of cooling by means of either thermal protector(s) or thermal
detector(s)
3.3
thermal detector
electrically insulated device that is only sensitive to temperature, capable of initiating a
switching function in a protection system when its temperature reaches a predetermined level
3.4
thermal protector
electrically insulated device that is sensitive to the temperature of the machine winding which
carries machine current, capable of directly switching off the machine when its temperature
reaches a predetermined level
Note 1 to entry: Some thermal protectors are sensitive to both temperature and current, the combination of which
activates the direct switching off of the machine.
3.5
thermal overload with slow variation
overload condition or loss of cooling that produces a rise of temperature that is sufficiently slow
that the temperature of the thermal protector or detector follows it without appreciable delay
3.6
thermal overload with rapid variation
overload condition or loss of cooling that produces a rise of temperature that is too rapid for the
temperature of the thermal protector or detector to follow without appreciable delay resulting in
a significant temperature difference between the thermal device and the part to be protected
3.7
maximum temperature after tripping
maximum value of the temperature that is reached by the protected part of the machine during
the period which follows tripping by the thermal protection system
3.8
direct thermal protection
form of protection where the part of the machine in which the thermal detector(s) or thermal
protector(s) are incorporated is the part for which protection is being provided
3.9
indirect thermal protection
form of protection where the part of the machine in which the thermal detector(s) or thermal
protector(s) are incorporated (e.g. the stator winding) is not the part for which protection is
being provided (e.g. the rotor winding)
4 Thermal protection limits
Machines shall be capable of operating at rated output and at all operating conditions according
to IEC 60034-1 without activation of the thermal protection device. The thermal protection
device shall limit the winding temperature in accordance with Clause 5 or Clause 6.
– 8 – IEC 60034-11:2020 © IEC 2020
5 Protection against thermal overloads with slow variation
When subjected to an overload or other misuse condition causing overheating with slow
variation, the protection system shall operate to prevent the temperature of the machine winding
from exceeding the values in Table 1.
Examples of the rise in temperature as a function of time are shown in Figure 1 and Figure 2.
Table 1 – Maximum winding temperatures for overloads with slow variation
Thermal class 130(B) 155(F) 180(H) 200(N)
145 170 195 215
Maximum insulated winding temperature °C
The winding temperature shall be determined by the resistance method in accordance with the
requirements of 8.6.2 of IEC 60034-1:2017.
NOTE 1 The limit values in Table 1 exceed the thermal classification and thus will reduce the lifetime of the motor.
NOTE 2 The maximum temperature limits are based on experience. Some of the ways in which a thermal overload
with slow variation may be caused are:
• Defects in ventilation or the ventilation system due to excessive dust in the ventilation ducts, or dirt on windings
or frame cooling ribs, etc.
• An excessive rise in ambient temperature or the temperature of the cooling medium.
• Gradual increasing mechanical overload.
• Prolonged voltage drop, over-voltage or unbalance in the machine supply.
• Excessive duty on a motor rated for intermittent duty.
• Frequency deviations.
Key
1 is the winding temperature in the vicinity of the thermal protector or detector
2 is the temperature of the thermal protector or detector
3 is the temperature when operating at normal duty
4 is the time at the beginning of the thermal overload
X axis is time
Y axis is temperature
Figure 1 – Example of thermal overload with slow variation
and direct thermal protection
Key
1 is the winding temperature in the vicinity of the thermal detector or protector
2 is the temperature of the thermal detector or protector
3 is the interval with normal cycling frequency
4 is the time at the beginning of the thermal overload
X axis is time
Y axis is temperature
Figure 2 – Example of thermal overload with slow variation in the case of too intensive
intermittent periodic duty with starting (duty S4) and direct thermal protection
6 Protection against thermal overloads with rapid variation
When a thermal overload with rapid variation is applied to the machine, the thermal protection
system shall operate to prevent the temperature of the machine winding from exceeding the
values given in Table 2.
A current overload relay does not normally provide protection against repeated rapid overload
variations and the use of a thermal protection device should be considered
Examples of the rise in temperature as a function of time are shown in Figure 3 and Figure 4.
Table 2 – Maximum winding temperatures for overloads with rapid variation
Thermal class 130(B) 155(F) 180(H) 200(N)
Maximum insulated winding temperature °C 225 250 275 295
The winding temperature shall be determined by direct measurements such as thermocouples
in accordance with the requirements of 8.5.3 of IEC 60034-1:2017.
It is understood that the motor winding may be permanently damaged and may not be able to
operate after it has been exposed to temperatures according to Table 2.
– 10 – IEC 60034-11:2020 © IEC 2020
NOTE 1 Some of the ways in which a thermal overload with rapid variation may be caused are:
• Stalling the motor.
• Phase failure.
• Starting under abnormal conditions, for example, inertia too great, voltage too low, load torque abnormally high;
• Sudden and significant increase in load.
• Starting repeatedly during a short time.
NOTE 2 The maximum temperature limits are based on experience, taking into account factors such as ambient
temperature, variations in supply voltage and normal requirements for starting motors.
The temperatures in Table 2 shall not be confused with the operating temperatures of the
winding’s thermal protector or thermal detector which have to be significantly below these
values. The thermal protector shall be installed at a place where the highest temperatures are
expected according to the application and the motor cooling system.
Key
1 is the maximum winding temperature after tripping
2 is the winding temperature in the vicinity of the thermal protector or detector
3 is the temperature when operating at normal duty
4 is the time at the beginning of the thermal overload
5 is the time at which tripping occurs
6 is the temperature of the thermal protector or detector
7 is the operating temperature of the thermal detector or protector
X axis is time
Y axis is temperature
Figure 3 – Example of thermal overload with rapid variation
where the thermally critical part has direct thermal protection
Key
1 is the maximum temperature after tripping
2 is temperature of the part which is the thermally critical part for a thermal overload with rapid variation
3 is the temperature when operating at normal duty
4 is the beginning of thermal overload with rapid variation
5 is the tripping time
6 is the temperature of the thermal detector or protector incorporated in the thermally critical part for thermal
overload with slow variation
7 is the temperature of the part which is not the thermally critical part of the thermal overload with rapid variation,
but which is the thermally critical part for a thermal overload with slow variation
X axis is time
Y axis is temperature
Figure 4 – Example of thermal overload with rapid variation
where the thermally critical part has indirect thermal protection
7 Restart after tripping
Before restarting a machine that has tripped, an investigation shall be made to try to identify
the cause of the operation of the machine protection. When attempting to restart the machine,
account shall be taken of the conditions stated in 6.3 or 9.3 of IEC 60034-12:2016.
The methods of protection included in this document only protect rotor windings indirectly. For
large motors (particularly 2 pole motors) and for motors starting large inertia loads, special
attention needs to be given to rotor heating both when starting and especially after a "trip" has
occurred.
NOTE The provision of the facility to enable machines to be automatically restarted after tripping is a matter for
special agreement taking full account of all safety implications.
– 12 – IEC 60034-11:2020 © IEC 2020
8 Type tests
8.1 General
Type tests are to verify the compliance of a thermal protection system with the requirements of
this document.
Tests shall be made on a machine which is representative of the machine type. The proposed
thermal protection system shall be installed.
Temperature sensors used for testing shall be located in positions representative of the location
of the thermal detectors used by the thermal protection system.
8.2 Verification of temperature due to the thermal overloads with slow variation
Starting with the machine at operating temperature, the load shall be slowly increased so that
the temperature of the winding increases at a rate of less than 1 K per 5 min. Temperatures
shall be recorded at a minimum of 10 min intervals.
When the thermal protection system trips, the supply to the machine shall be switched off if it is
not directly interrupted by the thermal protection device. The winding temperature shall be
determined immediately after tripping in accordance with the requirements of 8.6.2 of
IEC 60034-1:20
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Frequently Asked Questions
IEC 60034-11:2020 is a standard published by the International Electrotechnical Commission (IEC). Its full title is "Rotating electrical machines - Part 11: Thermal protection". This standard covers: IEC 60034-11:2020 specifies requirements relating to the use of thermal protectors and thermal detectors incorporated into the stator windings or placed in other suitable positions in induction machines in order to protect them against serious damage due to thermal overloads. It applies to single-speed three-phase 50 Hz or 60 Hz cage induction motors in accordance with IEC 60034-1 and IEC 60034-12 that: - have a rated voltage up to 1 000 V; - are intended for direct-on-line or star-delta starting. The main changes with respect to the previous edition are: - the additional specification of winding temperature limits for temperature class 200 (N), - the increased limits of maximum winding temperatures for overloads with rapid variation, - the clarification that the motor winding may be permanently damaged after it has been exposed to temperatures - a clarification of the definition of indirect thermal protection, - a clarification on the test methods for larger motors.
IEC 60034-11:2020 specifies requirements relating to the use of thermal protectors and thermal detectors incorporated into the stator windings or placed in other suitable positions in induction machines in order to protect them against serious damage due to thermal overloads. It applies to single-speed three-phase 50 Hz or 60 Hz cage induction motors in accordance with IEC 60034-1 and IEC 60034-12 that: - have a rated voltage up to 1 000 V; - are intended for direct-on-line or star-delta starting. The main changes with respect to the previous edition are: - the additional specification of winding temperature limits for temperature class 200 (N), - the increased limits of maximum winding temperatures for overloads with rapid variation, - the clarification that the motor winding may be permanently damaged after it has been exposed to temperatures - a clarification of the definition of indirect thermal protection, - a clarification on the test methods for larger motors.
IEC 60034-11:2020 is classified under the following ICS (International Classification for Standards) categories: 01 - GENERALITIES. TERMINOLOGY. STANDARDIZATION. DOCUMENTATION; 29.160.01 - Rotating machinery in general. The ICS classification helps identify the subject area and facilitates finding related standards.
IEC 60034-11:2020 has the following relationships with other standards: It is inter standard links to IEC 60034-11:2004. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
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