TC 2 - Rotating machinery

IEC 60034-12:2024 specifies the parameters for eight designs of starting performance of single-speed three-phase 50 Hz or 60 Hz cage induction motors in accordance with IEC 60034‑1 that:
- have a rated voltage up to 1 000 V;
- are intended for direct-on-line or star-delta starting;
- are rated on the basis of duty type S1;
- are constructed to any degree of protection as defined in IEC 60034-5 and explosion protection.
This document also applies to dual voltage motors provided that the flux saturation level is the same for both voltages. This fourth edition cancels and replaces the third edition published in 2016. Aligned with the requirements for explosion protected motors from TC31 WG27
- new clause on methods for measuring locked-rotor current and torque;
- new informative annex on the general current and torque characteristics with locked rotor;
- new informative annex on correction of voltage and frequency;
- aligned with the requirements for explosion protected motors from TC31 WG27.

IEC 60136:2024 applies primarily to brushes and brush-holders for cylindrical commutators and slip rings for electrical rotating machines. Some clauses of this document may cover other configurations, such as flat commutators or plain disks. It defines the dimensions of brushes and their components, together with their tolerances:
- dimensions of brush block (t, a, r),
- angles α and β,
- chamfer,
- flexibles (shunts),
- standard terminals.
It also covers the conventional designation of principal dimensions, the marking of brushes and the testing methods for the qualification of brushes after their manufacturing (except the brush grade material, covered by IEC 60413). This third edition cancels and replaces the second edition published in 1986 and Amendment 1:1995. This edition constitutes a technical revision.
Please refer to the Foreword of the document for a comprehensive listing of the changes with respect to the previous edition.

IEC 60034-2-2:2024 applies to large rotating electrical machines and establishes additional methods of determining separate losses and to define an efficiency supplementing IEC 60034‑2‑1. These methods apply when full-load testing is not practical and results in a greater uncertainty. The specific methods described are:
- Calibrated-machine method.
- Retardation method.
- Calorimetric method.
- Summation of losses for permanent magnet excited synchronous machines.
This second edition cancels and replaces the first edition published in 2010. This edition includes the following significant technical changes with respect to the previous edition:
- Layout and procedures aligned with IEC 60034-2-1 and IEC 60034-2-3.
- Annex A added: an informative procedure for the summation of losses for large permanent-magnet excited synchronous machines.

IEC 60034-2-1:2024 is intended to establish methods of determining efficiencies from tests, and also to specify methods of obtaining specific losses. This document applies to DC machines and to AC synchronous and induction machines of all sizes within the scope of IEC 60034-1 rated for mains operation. These methods may be applied to other types of machines such as rotary converters, AC commutator motors and single-phase induction motors. This third edition cancels and replaces the second edition of IEC 60034-2-1 published in 2014. This edition includes the following significant technical changes with respect to the previous edition:
- Harmonization of layout and requirements with IEC 60034-2-2 and IEC 60034-2-3.

IEC 60034-2-3:2024 specifies test methods and an interpolation procedure for determining losses and efficiencies of converter-fed motors. The motor is then part of a variable frequency power drive system (PDS) as defined in IEC 61800‑9‑2. This document also specifies procedures to determine motor losses at any load point (torque, speed) within the constant flux range (constant torque range, base speed range), the field weakening range and the overload range based on determination of losses at seven standardized load points. This procedure is applicable to any variable speed AC motor (induction and synchronous) rated according to IEC 60034-1 for operation on a variable frequency and variable voltage power supply. This second edition cancels and replaces the first edition of IEC 60034-2-3 published in 2020. This edition includes the following significant technical changes with respect to the previous edition:
- Harmonization of requirements and procedures with IEC 60034-2-1.
- Extension of the interpolation procedure to the field weakening range.

IEC 60034-30-3:2024 specifies efficiency classes for fixed-speed three-phase high-voltage cage induction motors in accordance with IEC 60034-1 that
- have a rated voltage exceeding 1 000 V, but not exceeding 11 kV;
- have a rated power from 200 kW to 2 000 kW;
This document provides the global harmonization of energy-efficiency classes of three-phase cage induction motors with rated voltage above 1 000 V that are rated for direct online starting and fixed-speed operation at a 50 Hz or 60 Hz supply with sinusoidal voltage.

IEC 60034-27-2:2023 deals with on-line PD measurements and provides a common basis with standardized procedures if possible for:
- measuring techniques and instruments;
- the arrangement of the installation;
- normalization and sensitivity assessment;
- measuring procedures;
- noise reduction;
- the documentation of results;
- the interpretation of results;
with respect to partial discharge on-line measurements on the stator winding insulation of non‑converter driven rotating electrical machines with rated voltage of 3 kV and up. This document covers PD measuring systems and methods detecting electrical PD signals. The same measuring devices and procedures can also be used to detect electrical sparking and arcing phenomena.

IEC 60034-18-1:2022 deals with the general guidelines for functional evaluation of electrical insulation systems, used or proposed to be used in rotating electrical machines within the scope of IEC 60034-1, in order to qualify them. IEC 60034-18-1 defines general requirements on the qualification of insulation systems, where – for thermal ageing – the Arrhenius equations do not necessarily fit, according to many experiences.
This third edition cancels and replaces the second edition published in 2010. This edition includes the following significant technical changes with respect to the previous edition:
a. provides general guidelines for functional evaluation of different types of windings as before but incorporates those changes, which have been introduced for the electrical qualification and evaluation of windings which are electrically stressed by converter-supply; b. is now focused on general guidelines with all technical details of procedures and qualification principles moved to the subsequent parts; c. details additional general aspects of functional evaluation and qualification, particularly the procedure for comparison between reference and candidate insulation systems, the introduction of the concept of qualification for different expected life-times in service and the evaluation of minor component or manufacturing changes.

IEC TS 60034-25:2022 describes the performance characteristics of AC electrical machines for use on converter supplies. For electrical machines specifically designed for converter duty application design features are defined. It also specifies the interface parameters and interactions between the electrical machine and the converter including installation guidance as part of a power drive system, but except for the voltage at the power interface which is described in IEC TS 61800-8. This fourth edition of IEC TS 60034-25 cancels and replaces the third edition, This edition includes the following significant technical changes with respect to the previous edition:
a. The definitions of a converter capable motor and a converter duty motor are added.
b. Clause 18 modified to include the performance expectations of a converter capable motor.
c. Clause 8 modified to update shaft currents section.
d. Annex D added to define the derating requirements.

IEC 60072-1:2022 is applicable for the majority of rotating electrical machines for industrial purposes within the dimension range and output powers.
- Foot- mounted: shaft heights: 56 mm to 400 mm
- Flange- mounted: pitch circle diameter of flange: 55 mm to 1 080 mm.
This seventh edition cancels and replaces the sixth edition published in 1991. This edition includes the following significant technical changes with respect to the previous edition:
a. modification of the series title;
b. complete revision on the basis of EN 50347;
c. integration of the relationships between frame size, shaft extensions, rated outputs and flange numbers;
d. additional tolerances and measurements for shafts;
e. modification of Annex A with additional frame numbers and relationships between frame size and rated power.

IEC 60034-1:2022 is applicable to all rotating electrical machines, except rotating electrical machines for rail and road vehicles, which are covered by the IEC 60349 series of standards. Machines within the scope of this document may also be subject to superseding, modifying or additional requirements in other standards, for example, IEC 60079 and IEC 60092. This fourteenth edition cancels and replaces the thirteenth edition published in 2017.

IEC 60034-33:2022 applies to three-phase salient-pole synchronous generators and synchronous motor-generators for hydraulic turbine and pump-turbine applications, that have rated frequency of 50 Hz or 60 Hz, rated output of 10 MVA and above, pole pair number 3 and above, and rated voltage of 6 kV and above. This document supplements basic requirements for rotating machines given in IEC 60034-1.

IEC 60034-18-32:2022 describes qualification procedures for the evaluation of electrical endurance of insulation systems for use in rotating electrical machines using form-wound windings energized with sinusoidal power frequency voltage. The test procedures for the main wall insulation are comparative in nature, such that the performance of a candidate insulation system is compared to that of a reference insulation system with proven service experience. If no reference system is available, the diagram in Annex A is available for use. The qualification procedures of inverter duty insulation system for form-wound windings can be found in IEC 60034-18-42 or IEC 60034-18-41. A new and informative test procedure for the stress control system is introduced and defined in Annex B.
This second edition cancels and replaces the first edition published in 2010. This edition includes the following significant technical changes with respect to the previous edition:
a. Title modified.
b. Simplification of clauses.
c. Reduction in the number of test procedures.
d. Inclusion of full bars and coils as test objects.
e. A new clause dealing with failures and failure criteria.

IEC 60034-9:2021 specifies test methods for the determination of sound power level of rotating electrical machines and specifies maximum A-weighted sound power levels for factory acceptance testing of network-supplied, rotating electrical machines in accordance with lEC 60034-1, having methods of cooling according to lEC 60034-6 and degrees of protection according to lEC 60034-5, and having the following characteristics:
- standard design, either AC or DC, without additional special electrical, mechanical, or acoustical modifications intended to reduce the sound power level
- rated output from 1 kW (or kVA) up to and including 5 500 kW (or kVA)
- rated speed not greater than 3 750 min–1
This fifth edition cancels and replaces the fourth edition, published in 2003 and its amendment 1, published in 2007. This edition includes the following significant technical changes with respect to the previous edition:
a) In Table 2 and Table 3 cooling methods IC01, IC11, IC21 and IC31, IC71, IC81 are now covered.
b) This edition adds Table 3 for 60 Hz machines, whereas Table 2, which covers only 50 Hz machines, has no change in levels.
c) In Table 3, grade A is added to harmonize the highest levels seen in IEC and NEMA, whereas grade B was added to harmonize the lowest, more restrictive levels seen in IEC and NEMA.
d) The clause “Determination of noise increments caused by converter supply” has been shifted to Annex B and renamed “Information on typical noise increments caused by converter supply”.

IEC 60773:2021 applies to test methods for the measurement of the operational characteristics of brushes designed to operate on commutating and slip ring machines under specified test conditions. By extension some tests may be relevant for other kinds of sliding electrical contacts for electrical appliances.
This second edition cancels and replaces the first edition published in 1983. This edition includes the following significant technical changes with respect to the previous edition:
- the clause structure has been modified on the view point of a laboratory testing procedure. The new sequence is as follows: test rig specification, general testing procedure, and specific procedure for each operational characteristic
- a new clause has been added to introduce the black-band test for the characterisation of the brush grades for DC machines.

IEC TS 60034-27-5:2021 provides an off-line measurement method of the partial discharge inception and extinction voltage on winding insulation under repetitive impulse voltage. This document is relevant to rotating machines supplied by a voltage source converter.

IEC TS 60034-34:2020 is applicable to AC adjustable speed rolling mill motors and identifies specific requirements for AC adjustable speed rolling mill motors, where those performance characteristics are different from those for conventional AC motors.
Various types of overload capacity conditions and overloads are defined. The possible effect on motor insulation life due to operating the motor beyond its design capability is discussed.
Requirements for confirmation of motor under specified variable speed operational conditions are introduced.

IEC 60034-7:2020 specifies the IM Code, a classification of types of construction, mounting arrangements and the terminal box position of rotating electrical machines. Two systems of classification are provided as follows:
- Code I: An alpha-numeric designation applicable to machines with end-shield bearing(s) and only one shaft extension
- Code II: An all-numeric designation applicable to a wider range of types of machines including types covered by Code I.
This third edition cancels and replaces the second edition, published in 1992, and its Amendment 1:2000. The main technical changes with regard to the previous edition are as follows:
- note on twin motors added
- reference to 4.3 instead of duplication of text
- new subclause on marking of shaft inclination or declination.
The contents of the corrigendum of March 2023 have been included in this copy.

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 60034-18-42:2017 defines criteria for assessing the insulation system of stator/rotor windings of single or polyphase AC machines which are subjected to repetitive impulse voltages, such as those generated by pulse width modulation (PWM) converters, and are expected to experience and withstand partial discharge activity during service. It specifies electrical qualification tests on representative specimens to verify fitness for operation with voltage-source converters. It also describes an additional classification system which defines the limits of reliable performance under converter-fed conditions.

IEC 60034-3:2020 applies to large three-phase synchronous generators, having rated outputs of 10 MVA and above driven by steam turbines or combustion gas turbines. Also included are synchronous Mvar compensators of the same output range connected to a grid for the purpose of exchanging reactive power. This document supplements basic requirements for rotating machines given in IEC 60034-1.
This seventh edition cancels and replaces the sixth edition published in 2007. This edition includes the following significant technical changes with respect to the previous edition:
- title modified;
- scope extended to synchronous compensators;
- rotor overcurrent requirements added;
- impact of stator harmonics on rotor unbalanced load capability introduced;
- synchronisation requirements added;
- adjustments of temperatures or temperature rise revised for gas turbine applications;
- requirements for auxiliaries updated.

IEC 60034-5:2020 applies to the classification of degrees of protection provided by enclosures for rotating electrical machines. It defines the requirements for protective enclosures that are in all other respects suitable for their intended use and which, from the point of view of materials and workmanship, ensure that the properties dealt with in this document are maintained under normal conditions of use. This document does not specify degrees of protection against mechanical damage of the machine, or conditions such as moisture (produced for example by condensation), corrosive dust and vapour, fungus or vermin.
This document is also applicable to explosion proof machines, but it does not specify the types of protection for use in a potentially explosive (dust, gas) environment. Those are defined in the IEC 60079 series of standards. This document gives definitions for standard degrees of protection provided by enclosures applicable to rotating electrical machines as regards the:
a. protection of persons against contacts with or approach to live parts and against contact with moving parts (other than smooth rotating shafts and the like) inside the enclosure and protection of the machine against ingress of solid foreign objects
b. protection of machines against the harmful effects due to ingress of water;
c. protection of machines against the harmful effects due to ingress of dust.
This fifth edition cancels and replaces the fourth edition, published in 2000, and its Amendment 1:2006.The main technical changes with respect to the previous edition are:
- the inclusion of an additional second numeral 9 including its test method,
- an additional note for clarification in Table 3,
- a clarification on the term open drain hole,
- a clarification on the ingress of dust in Table 4,
- pressure values given now in Pa only,
- a clarification in the scope on the applicability of this standard for (Ex) motors,
- a new Clause 3 with definitions,
The contents of the corrigendum of January 2024 have been included in this copy.

IEC 60034-2-3:2020 specifies test methods and an interpolation procedure for determining losses and efficiencies of converter-fed motors within the scope of IEC 60034-1:2017. The motor is then part of a variable frequency power drive system (PDS) as defined in IEC 61800‑9‑2:2017.
Applying the approach of the comparable converter, the motor efficiency determined by use of this document is applicable for comparison of different motor designs only.
The document also specifies procedures to determine motor losses at any load point (torque, speed) within the base speed range (constant torque range, constant flux range) based on determination of losses at seven standardized load points. This procedure is applicable to any variable speed AC motor (induction and synchronous) rated according to IEC 60034-1:2017 for operation on a variable frequency and variable voltage power supply.

The contents of the corrigendum of December 2020 have been included in this copy.

IEC 60034-23:2019 covers the procedures necessary to ensure the satisfactory repair, overhaul, and reclamation of all types and sizes of rotating electrical machines covered by IEC 60034.
This standard creates a generic industry procedure covering common aspects of a complete repair. The scope of work depends on the machine type, rating, condition, and the importance of plant reliability and safety. This standard does not supersede the requirements prescribed in IEC 60079-19 or elsewhere concerning the repair and overhaul for machines used in explosive atmospheres.
This first edition cancels and replaces IEC TS 60034-23 published in 2003. This edition includes the following significant technical changes with respect to the previous edition:
– the title of the standard has been changed to Rotating electrical machines – Part 23: Repair, overhaul and reclamation;
– general Principles added to cover: hazardous areas, traction motors, machine efficiency, environment, end of life recycling. and circular economy considerations;
– general: Scope of work, health and safety, standards, quality, information required and documentation now covered;
– final tests updated;
– additional requirements for the repair and testing of DC machines added;
– additional requirements for the repair and testing of High Voltage AC machines added;
– customer reports and handover added;
– new standard tolerances added.

IEC 60034-14:2018 specifies the factory acceptance vibration test procedures and vibration limits for certain electrical machines under specified conditions, when uncoupled from any load or prime mover. It is applicable to DC and three-phase AC machines, with shaft heights 56 mm and higher and a rated output up to 50 MW, at operational speeds from 120 min–1 up to and including 15 000 min–1. This new edition includes the following significant technical changes with respect to the previous edition:
- Improved explanation of the definition “free suspension”.
- Addition of an alternative method of rigid mount
- Definition of an improved option for shaft key.

IEC 60276:2018 applies to carbon brushes for electrical machinery. This edition applies only to carbon brushes for commutators and slip-rings in rotating machines. Terms and definitions are relative to the brush construction (references 100’s to 500’s and parts of 900’s) and to the markings when operating on a rotating machine (references 600’s to 800’s).
This new edition includes the following significant technical changes with respect to the previous edition:
Some nomenclature has been deleted or added, whereas remaining definitions have been detailed and clarified, to reflect the technical evolution since 1987.
Additional definitions have been included to address the request for reviewing this standard, in particular nomenclature of commutator/slip-rings markings, brush markings and commutation sparks codes.

IEC 60034-4-1:2018 applies to three-phase synchronous machines of 1 kVA rating and larger and describes methods intended to be used for machines having an excitation winding with slip-rings and brushes for their supply. Synchronous machines with brushless excitation require special effort for some of the tests. For machines with permanent magnet excitation, there is a limited applicability of the described tests, and special precautions should be taken against irreversible demagnetization.

IEC 60034-27-4:2018 provides recommended test procedures for the measurement of insulation resistance and polarization index of stator and rotor winding insulation of rotating electrical machines. This document recommends minimum acceptable values of insulation resistance and polarization index of winding insulation valid for fully processed low and high voltage AC and DC rotating electrical machines with a rated power of 750 W or higher.

IEC 60034-27-1:2017 provides a common basis for:
- measuring techniques and instruments;
- the arrangement of test circuits;
- normalization and testing procedures;
- noise reduction;
- the documentation of test results;
- the interpretation of test results,
with respect to partial discharge off-line measurements on the winding insulation of rotating electrical machines.
This International Standard cancels and replaces IEC TS 60034-27 (2006). It constitutes a technical revision and reflects numerous improvements and corrections with respect to the previous publication.

IEC 60034-1:2017 is applicable to all rotating electrical machines except those covered by other IEC standards, for example, IEC 60349. Machines within the scope of this document may also be subject to superseding, modifying or additional requirements in other standards, for example, IEC 60079 and IEC 60092. This new edition contains a number of clarifications, corrections and enhancements with regard to the previous edition.

IEC TS 60034-32:2016(E) is intended to provide consistent guidelines for measuring and reporting end-winding vibration behaviour during operation and at standstill. It
- defines terms for measuring, analysis and evaluation of stator end-winding vibration and related structural dynamics;
- gives guidelines for measuring dynamic / structural characteristics offline and stator end-winding vibrations online;
- describes instrumentation and installation practices for end-winding vibration measurement equipment;
- establishes general principles for documentation of test results;
- describes the theoretical background of stator end-winding vibrations. This part of IEC 60034 is applicable to three-phase synchronous generators and three-phase synchronous direct online (DOL) motors.

IEC TS 60034-30-2:2016(E) specifies efficiency classes for variable speed rotating electric machines not covered in IEC 60034-30-1. The classification only covers machines designed for operation with sinusoidal fundamental current that are not designed to be operated direct on-line (grid), for example permanent magnet synchronous machines with and without additional reluctance torque, sinusoidal reluctance synchronous machines and synchronous machines with DC field windings.

IEC 60034-12:2016 specifies the parameters for eight designs of starting performance of single-speed three-phase 50 Hz or 60 Hz cage induction motors in accordance with IEC 60034-1 that:
- have a rated voltage up to 1 000 V;
- are intended for direct-on-line or star-delta starting;
- are rated on the basis of duty type S1;
- are constructed to any degree of protection and explosion protection. The main changes with respect to the previous edition are as follows:
- new design letter E for extended efficiency motors, explanation of all design letters, and description of new designs NE, NEY, HE, and HEY;
- addition of a reference to IEC 60079-7;
- addition of a formula to calculate locked rotor current from apparent power.

IEC TR 63021:2016(E) presents technical characteristics, application results and practical information on NG-brush for slip-ring obtained through the application of NG-brush in various kinds of wound rotor-type induction motor (large-size water pump, belt conveyer, lift, winder motor, grinding mill and crusher in coal or ore mine; crane, rolling mill, compressor and winder motor for boring in oil or gas facility).

IEC 60034-27-3:2015 provides guidelines for the test procedures and the interpretation of test results for dielectric dissipation factor measurements on the stator winding insulation of rotating electrical machines. These guidelines are valid for rotating electrical machines with conductive slot coatings operating at a rated voltage of 6 kV and higher. This standard applies to individual form-wound stator bars and coils outside a core (uninstalled), individual stator bars and coils installed in a core and complete form-wound stator winding of machines in new or aged condition. This edition includes the following significant technical changes with respect to the previous publication IEC TR 60894:1987:
- inclusion of digital measurement of dissipation factor and capacitance;
- inclusion of limits for dissipation factor values;
- detailed description of measuring techniques; extension of scope to complete windings.

IEC TS 60034-25:2014 describes the performance characteristics of a.c. electrical machines for use on converter supplies. For electrical machines specifically designed for converter duty application design features are defined. It also specifies the interface parameters and interactions between the electrical machine and the converter including installation guidance as part of a power drive system, but except for the voltage at the power interface which is described in IEC 61800-8. The main technical changes with regard to the previous edition are as follows:
- merging of IEC TS 60034-17 into IEC TS 60034-25 adding a clause which now includes all specific requirements for standard non-definite purpose electric machines;
- removal of Annex C: Noise increments due to converter supply.

IEC 60034-19:2014 applies to d.c. machines rated 1 kW and above operating on rectifier-fed power supplies, d.c. buses or other d.c. sources and provides standardized methods intended to determine characteristic quantities for conventional and rectifier-fed d.c. machines. These methods supplement the requirements in IEC 60034-1 and IEC 60034-2-1. The main changes with regard to the previous edition are as follows:
- description of the procedure for black band testing has been detailed and clarified;
- procedures for measurement of the magnetization curves under no-load and load conditions have been added.

IEC 60034-2-1:2014(B) is intended to establish methods of determining efficiencies from tests, and also to specify methods of obtaining specific losses. This standard applies to d.c. machines and to a.c. synchronous and induction machines of all sizes within the scope of IEC 60034-1. This new edition includes the following significant technical changes with respect to the previous edition: grouping of the test methods into preferred methods and methods for field or routine testing; addition of the details of the requirements regarding instrumentation; addition of the description of tests required for a specific method in the same sequence as requested for the performance of the test.

IEC 60034-30-1:2014 specifies efficiency classes for single-speed electric motors that are rated according to IEC 60034-1 or IEC 60079-0, for operation on a sinusoidal voltage supply. This standard establishes a set of limit efficiency values based on frequency, number of poles and motor power. No distinction is made between motor technologies, supply voltage or motors with increased insulation designed specifically for converter operation even though these motor technologies may not all be capable of reaching the higher efficiency classes. This makes different motor technologies fully comparable with respect to their energy efficiency potential.

IEC 60034-18-41:2014 defines criteria for assessing the insulation system of stator/rotor windings which are subjected to voltage-source pulse-width-modulation drives. It applies to stator/rotor windings of single or polyphase AC machines with insulation systems for converter operation. It describes qualification tests and quality control (type and routine) tests on representative samples or on completed machines which verify fitness for operation with voltage source converters.

IEC 60034-28:2012 applies to three-phase low-voltage cage induction motors of frame numbers 56 to 400 as specified in IEC 60072-1. This standard establishes procedures to obtain values for elements of single phase equivalent circuit diagrams from tests and defines standard elements of these diagrams. This edition includes the following significant technical changes with respect to the previous edition:
- the formulae are now all given for equivalent star-connection equivalent circuit diagrams;
- procedures for the determination of equivalent circuit parameters from a load curve test as an alternative to the reverse rotation and locked rotor tests have been added.

IEC 60034-18-21:2012 gives test procedures for the thermal evaluation and classification of insulation systems used or proposed for use in wire-wound alternating current (a.c.) or direct current (d.c.) rotating electrical machines. The test performance of a candidate insulation system is compared to the test performance of a reference insulation system with proven service experience. The main technical changes with regard to the previous edition can be seen in the introduction of some basic statistical methods in the evaluation of comparative data. Moreover, the standard states a simpler use of different test procedures.

IEC 60034-18-31:2012 describes thermal endurance test procedures for classification of insulation systems used in a.c. or d.c. rotating electrical machines with indirect cooling and form-wound windings. These test procedures are intended to compare the thermal endurance performance of the mainwall insulation between conductor(s) and ground and, where required by the design of the coil or bar, the insulation between the turns. The main technical changes with regard to the previous edition include:
- Definition of the test method and sub-cycles required to establish a consistent standardized platform for thermal ageing of insulation systems for form-wound windings.
- Recommendations for establishing a thermal life curve based on confidence intervals.
- Comparison of candidate and reference system performance for specific requirements of thermal class, within feasible limits. Keywords: rotating machinery, insulation systems