IEC 60034-2-3:2020

Rotating electrical machines - Part 2-3: Specific test methods for determining losses and efficiency of converter-fed AC motors

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.

Machines électriques tournantes - Partie 2-3: Méthodes d'essai spécifiques pour la détermination des pertes et du rendement des moteurs à courant alternatif alimentés par convertisseur

l'IEC 60034-2-3:2020 spécifie les méthodes d’essai et la procédure d’interpolation relatives à la détermination des pertes et des rendements des moteurs alimentés par convertisseur relevant du domaine d’application de l’IEC 60034-1:2017. Le moteur est alors considéré comme faisant partie intégrante d'un système d’entraînement électrique de puissance (PDS – power drive system) à fréquence variable, comme cela est défini dans l’IEC 61800-9-2:2017.
Avec l’approche du convertisseur comparable, le rendement du moteur déterminé par l’utilisation du présent document s’applique uniquement à la comparaison des différentes conceptions de moteurs.
Le document spécifie également des procédures de détermination des pertes du moteur en tout point de charge (couple, vitesse) dans la plage de vitesses de base (plage de couples constants, plage de flux constants) à partir de la détermination des pertes au niveau de sept points de charge normalisés. Cette procédure s’applique à tout moteur à courant alternatif à vitesse variable (à induction et synchrone) assigné selon l’IEC 60034-1:2017 pour un fonctionnement à fréquence variable et alimenté en tension variable.

General Information

• Status: Published
• Publication Date: 18-Mar-2020
• ICS: 29.160.01 - Rotating machinery in general
• Technical Committee: TC 2 - Rotating machinery
• Drafting Committee: WG 28 - TC 2/WG 28
• Current Stage: DELPUB - Deleted Publication
• Start Date: 12-Mar-2024
• Completion Date: 04-Apr-2022

Relations

• Revises: IEC TS 60034-2-3:2013 - Rotating electrical machines - Part 2-3: Specific test methods for determining losses and efficiency of converter-fed AC induction motors
• Effective Date: 05-Sep-2023
• Revised: IEC 60034-2-3:2024 - Rotating electrical machines - Part 2-3: Specific test methods for determining losses and efficiency of converter-fed AC motors
• Effective Date: 05-Sep-2023

Overview

IEC 60034-2-3:2020 is an international standard published by the International Electrotechnical Commission (IEC) that specifies test methods for determining the losses and efficiency of converter-fed AC motors. This standard applies to variable speed AC motors, including both induction and synchronous types, operated within the base speed range under variable frequency and voltage power supplies. It supplements the general requirements of IEC 60034-1:2017 by focusing specifically on converter-fed motors as part of variable frequency power drive systems (PDS) defined in IEC 61800-9-2:2017.

The core purpose of IEC 60034-2-3:2020 is to provide a reliable methodology for assessing total motor losses-including additional high-frequency losses caused by converter operation-and overall motor efficiency. This enables fair comparison of motor performance across different designs when powered by comparable converters.

Key Topics

• Test Methods and Procedures
  The standard details multiple test approaches for evaluating motor efficiency when fed from power converters:

  • Direct measurement of input and output power (Method 2-3-A)
  • Summation of losses with determination of additional high-frequency losses (Method 2-3-B)
  • Alternate Efficiency Determination Method (AEDM)
  • Efficiency calculation based on interpolation of losses

• Standardized Operating Points
  IEC 60034-2-3 defines seven standardized load points across the torque and speed ranges to characterize motor losses and efficiency comprehensively. These points facilitate consistent testing and benchmarking.

• Interpolation of Losses
  The standard provides a detailed interpolation procedure to estimate motor losses at any arbitrary load and speed point within the motor’s base speed range. This allows manufacturers and users to predict performance under various operating conditions.

• Instrumentation and Converter Setup
  Specific recommendations cover the use of precise measurement instruments such as power analyzers and torque transducers, plus guidance on converter configurations to ensure accurate and reproducible loss measurements.

• High-Frequency Loss Considerations
  Unlike sinusoidal supply scenarios, converter-fed motors experience additional high-frequency losses caused by switching characteristics of the drive. IEC 60034-2-3 includes protocols to quantify these losses, which are critical for realistic efficiency evaluation.

Applications

IEC 60034-2-3:2020 is vital to industries and sectors where energy efficiency, motor reliability, and performance optimization are critical and where variable frequency drives (VFDs) are prevalent. Typical applications include:

• Industrial Automation and Process Control
  Precise determination of losses helps optimize motor-drive systems for production lines, reducing energy consumption and operational costs.

• HVAC Systems
  Motors controlling fans, pumps, and compressors often use variable speed drives-this standard enables effective efficiency assessment to meet sustainability goals.

• Renewable Energy Systems
  In wind or solar-powered applications with converter-fed motors, quantifying losses ensures system efficiency and reliability.

• Electric Vehicles and Transportation
  Accurate efficiency measurements of converter-fed traction motors contribute to better battery life and vehicle performance.

• Product Development and Quality Control
  Motor manufacturers use the test methods to develop more efficient designs and verify compliance with regulatory requirements.

Related Standards

• IEC 60034-1:2017 – Defines general motor rating, performance, and testing guidelines applicable to all rotating electrical machines.
• IEC 61800-9-2:2017 – Provides definitions and requirements for variable frequency power drive systems, complementing the scope of IEC 60034-2-3.
• IEC 60034-2-1:2014 – Specifies methods for measuring losses and efficiency on motors supplied by sinusoidal power, serving as a baseline comparison for converter-fed test methods.
• Additional IEC 60034 Series – Covers other parts related to construction, testing, and performance of rotating electrical machines optimizing comprehensive compliance.

---

IEC 60034-2-3:2020 offers a robust framework for assessing and comparing the efficiency of modern converter-fed AC motors, supporting energy efficiency initiatives and facilitating innovation in motor and drive technology across varied industries. By adhering to these international test standards, manufacturers, engineers, and end-users can ensure reliable, comparable, and precise motor performance data under converter supply conditions.

Standards Content (Sample)

IEC 60034-2-3 ®
Edition 1.0 2020-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Rotating electrical machines –
Part 2-3: Specific test methods for determining losses and efficiency of
converter-fed AC motors
Machines électriques tournantes –
Partie 2-3: Méthodes d'essai spécifiques pour la détermination des pertes
et du rendement des moteurs à courant alternatif alimentés par convertisseur

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IEC 60034-2-3 ®
Edition 1.0 2020-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Rotating electrical machines –

Part 2-3: Specific test methods for determining losses and efficiency of

converter-fed AC motors
Machines électriques tournantes –

Partie 2-3: Méthodes d'essai spécifiques pour la détermination des pertes

et du rendement des moteurs à courant alternatif alimentés par convertisseur

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.160.01 ISBN 978-2-8322-7842-0

– 2 – IEC 60034-2-3:2020 © IEC 2020
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 8
2 Normative references . 8
3 Terms and definitions . 8
4 Symbols and abbreviated terms . 9
5 Basic requirements . 10
5.1 Instrumentation . 10
5.1.1 General . 10
5.1.2 Power analyser and transducers . 10
5.1.3 Mechanical output of the motor . 11
5.2 Converter set-up . 11
5.2.1 General . 11
5.2.2 Comparable converter set-up for rated voltages up to 1 kV . 11
5.2.3 Testing with converters with rated voltages above 1 kV . 12
5.2.4 Testing with other converters . 12
6 Test method for the determination of the efficiency of converter-fed motors . 12
6.1 Selection of determination method . 12
6.2 Method 2-3-A – Direct measurement of input and output . 13
6.2.1 Test set-up . 13
6.2.2 Test procedure . 13
6.2.3 Efficiency determination. 13
6.2.4 Measurement at seven standardized operating points . 14
6.3 Method 2-3-B – Summation of losses with determination of additional high
frequency loss at converter supply at no-load operation . 14
6.3.1 General . 14
6.3.2 Test set-up . 14
6.3.3 Test procedure . 14
6.3.4 Efficiency determination. 15
6.4 2-3-C – Alternate Efficiency Determination Method (AEDM) . 15
6.5 2-3-D – Determination of efficiency by calculation . 15
7 Interpolation of losses at any operating point . 16
7.1 General . 16
7.2 Interpolation procedure . 16
7.3 Analytical determination of relative losses at any operating point . 16
7.4 Additional losses due to frequency converter voltage drop . 18
7.5 Alternate operating points to determine interpolation coefficients . 18
7.6 Optional determination of interpolation error . 19
Annex A (informative) Losses of AC motors . 21
A.1 General . 21
A.2 Stator and rotor winding I R losses P (P + P ) . 21
LSR LS LR
A.3 Iron losses (P ) . 21
Lfe
A.4 Additional load losses (P ) . 22
LL
A.5 Friction and windage losses (P ) . 22
Lfw
A.6 Additional high frequency losses (P ) . 23
LHL
Annex B (informative) Exemplary determination of losses and efficiency at various
load points . 24
B.1 General . 24
B.2 Determination of the interpolation coefficients . 24
B.3 Calculation of losses and efficiency for certain operating points . 25
Bibliography . 27

Figure 1 – Standardized operating points . 17

Table 1 – Preferred test methods . 12
Table 2 – Other test methods . 13
Table 3 – Normative operating points . 17
Table 4 – Non-normative alternate operating points . 19
Table A.1 – Recommended split of windage and friction losses for IC 411 self-
ventilated motors . 22
Table B.1 – Name plate data . 24
Table B.2 – Reference values . 24
Table B.3 – Losses for the 7 operating points . 25
Table B.4 – Interpolation coefficients . 25
Table B.5 – User-defined operating points . 26
Table B.6 – Calculated losses for the user-defined operating points . 26

– 4 – IEC 60034-2-3:2020 © IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ROTATING ELECTRICAL MACHINES –

Part 2-3: Specific test methods for determining losses and
efficiency of converter-fed AC motors

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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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 60034-2-3 has been prepared by IEC technical committee 2:
Rotating machinery.
This first edition cancels and replaces IEC TS 60034-2-3, published in 2013.
The text of this International Standard is based on the following documents:
FDIS Report on voting
2/1974/FDIS 2/1982/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.

– 6 – IEC 60034-2-3:2020 © IEC 2020
INTRODUCTION
The objective of this document is to define test methods for determining total losses including
additional high frequency motor losses and efficiency of converter-fed motors. Additional high
frequency losses appear in addition to the losses on nominally sinusoidal power supply as
determined by the methods of IEC 60034-2-1:2014. Results determined according to this
document are intended to allow comparison of losses and efficiency of different motors when
fed by converters.
Furthermore, the document gives seven standardized operating points to characterize the
development of losses and efficiency across the whole torque/speed range. An interpolation
procedure is provided to calculate losses and efficiency at any operating point (torque, speed).
In power-drive systems (PDS), the motor and the frequency converter are often manufactured
by different suppliers. Motors of the same design are produced in large quantities. They may
be operated from the grid or from frequency converters of many different types, supplied by
many different manufacturers. The individual converter properties (switching frequency, DC link
voltage level, etc.) will also influence the system efficiency. As it is impractical to determine
motor losses for every combination of motor, frequency converter, connection cable, output
filter and parameter settings, this document describes a limited number of approaches,
depending on the voltage level and the rating of the machine under test.
The losses determined according to this document are not intended to represent the losses in
the final application. They provide, however, an objective basis for comparing different motor
designs with respect to suitability for converter operation.
In general, when fed from a converter, motor losses are higher than during operation on a
nominally sinusoidal system. The additional high frequency losses depend on the harmonic
spectrum of the impressed converter output quantity (either current or voltage) which is
influenced by its circuitry and control method. For further information,
see IEC TS 60034-25:2014.
It is not the purpose of this document to define test procedures either for power drive systems
or for frequency converters alone.
Comparable converter
Latest experience and theoretical analysis have shown that the additional high frequency motor
losses generally do not increase much with load. The methods in this document are mainly
based on supplies from converters with pulse width modulation (PWM).
With respect to these types of converters and the growing need for verification of compliance
with national energy efficiency regulations, this document defines a so-called comparable
converter for testing of low voltage motors.
In principle, the comparable converter is a voltage source with a typical high frequency harmonic
content supplying the machine under test. It is not applicable to medium voltage motors.
Limitations for the application of the comparable converter
It has to be noted that the test method with the comparable converter described herein is a
standardized method intended to give comparable efficiency figures for standardized test
conditions. A motor ranking with respect to suitability for converter operation may be derived,
but it is not equivalent to determining of the actual motor losses for operation with a specific
converter which requires a test of the whole power drive system (PDS) with the specific
converter used in the final application.

Deviations are also expected for motors driven by multi-level voltage source or current source
converters where the additional high frequency motor losses differ much more depending on
speed and load than for two-level voltage source converters. Hence the determination of losses
and efficiency should preferably use procedures where the motor is operated together with the
same converter with which it is driven in service.
Another option is the determination of the additional high frequency motor losses by calculation.
If this is requested by the customer, the pulse pattern of the converter is required. Such
procedures are not part of this document.
The provided interpolation procedure for the determination of losses and efficiency at any
operating point (torque, speed) is limited to the base speed range (constant torque range,
constant flux range).
– 8 – IEC 60034-2-3:2020 © IEC 2020
ROTATING ELECTRICAL MACHINES –

Part 2-3: Specific test methods for determining losses and
efficiency of converter-fed AC motors

1 Scope
This part of IEC 60034 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.
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 60034-2-1:2014, Rotating electrical machines – Part 2-1: Standard methods for
determining losses and efficiency from tests (excluding machines for traction vehicles)
IEC 61000-2-4:2002, Electromagnetic compatibility (EMC) – Part 2-4: Environment –
Compatibility levels in industrial plants for low-frequency conducted disturbances
IEC 61800-9-2:2017, Adjustable speed electrical power drive systems – Part 9-2: Ecodesign for
power drive systems, motor starters, power electronics and their driven applications – Energy
efficiency indicators for power drive systems and motor starters
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60034-1:2017,
IEC 60034-2-1:2014 as well as the following 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
motor losses with converter supply
when powered by a converter, motor losses are a combination of losses caused by fundamental
frequency and losses caused by the converter high frequencies
3.2
fundamental losses
fundamental losses in the motor can be segregated into five different components: iron losses
(varying with motor frequency and applied fundamental voltage), friction and windage losses
(varying with motor speed), rotor winding losses, stator winding losses and additional load
losses (all three varying with motor current). Fundamental losses are the losses of a motor
running with application of rated voltage at fundamental frequency that does not contain any
further high frequencies.
3.3
additional high frequency losses
additional high frequency losses are produced in the motor by the non-sinusoidal voltage and
current waveforms generated by the converter and are in addition to the losses of iron, friction
and windage, rotor winding, stator winding and additional load loss (fundamental losses)
3.4
base speed range
speed range from standstill up to the highest speed where the motor can be supplied with a
voltage that changes in proportion to the speed so that the magnetic flux remains constant
(constant ratio U/f) for induction machines and according to the MTPA (maximum torque per
ampere) for synchronous machines. Within the base speed range, the maximum motor torque

is constant (constant torque range), if constant flux control is used.
3.5
switching frequency
number of switching events of one semiconductor within one second. It determines, together
with the selected pulse pattern and the converter topology, the lowest frequency of non-
controllable high frequencies or inter-harmonics at the IPC (in-plant point of coupling) or the
motor
Note 1 to entry: For a two level converter, the pulse frequency measured phase to phase is two times the switching
frequency defined in 3.5 in case of continuous modulation and about 1,33 times the switching frequency defined in
3.5 in case of discontinuous modulation. A switching event is once on and once off of one semiconductor.
4 Symbols and abbreviated terms
f Frequency, Hz
f Fundamental motor frequency, Hz
Mot
f Rated motor frequency, Hz
N
f Switching frequency, Hz
sw
I No-load current, A
I Rated current, A
N
MTPA Maximum torque per ampere control applied to synchronous motors
−1
n Speed, min
−1
n Rated speed, min
N
−1
n Reference speed, min
ref
P Power, W
P Constant losses at converter supply, W
Ccon
– 10 – IEC 60034-2-3:2020 © IEC 2020
P Constant losses at sinusoidal supply according to IEC 60034-2-1:2014, W
Csin
PDS Power drive system
P Additional high frequency loss due to converter supply, W
LHL
P Rated power, W
N
P Reference power, W
ref
P Motor input power at converter supply, W
1C
P Motor input power as tested according to IEC 60034-2-1:2014, W
1_60034-2-1
P Motor output power at converter supply, W
2C
P Motor output power as tested according to IEC 60034-2-1:2014, W
2_60034-2-1
PWM Pulse width modulation
T Machine torque, Nm
T Machine torque at converter supply, Nm
C
T Rated torque, Nm
N
T Reference torque, Nm
ref
U Rated motor voltage, V
N
η Efficiency
5 Basic requirements
5.1 Instrumentation
5.1.1 General
Unless otherwise stated in this document, the arithmetic average of the three line currents and
voltages shall be used.
When testing electric machines under load, slow fluctuations in the output power and other
measured quantities may be unavoidable. Therefore for each load point many readings shall be
taken automatically by a suitable digital meter over a period of at least 15 s but not more than
60 s and this average shall be used for the determination of efficiency.
Considering the high frequencies involved in converters feeding AC motors and their
contribution to the motor losses, the measuring equipment has to be selected according to the
range of relevant frequencies with sufficient accuracy.
For temperature measurements, a thermosensor installed in the hot spot may be optionally
used, as described in IEC 60034-2-1:2014.
5.1.2 Power analyser and transducers
The instrumentation for measuring power and current at the motor’s input shall basically meet
the requirements of IEC 60034-2-1:2014, but due to higher frequency components the following
additional requirements shall also apply.
The specified uncertainty of the power meters shall be 0,2 % of the rated apparent power of the
motor or better for the total active power at 50 Hz or 60 Hz. This is the total uncertainty of the
power meter including possible sensors.
NOTE 1 For example, when a three-phase motor has a rated voltage of 400 V and a rated current of 10 A then the
power meter's active power uncertainty is at least 0,2 % of √3 times 4 000 VA, which is 13,9 W or better.

The bandwidth of power meters and sensors shall be sufficiently wide that the error in the
measurement of total active power for the entire frequency range (beyond 50 Hz and 60 Hz) is
less than or equal to 0,3 % of the apparent power.
NOTE 2 In general, a bandwidth from 0 Hz up to 10 times of switching frequency is sufficient.
It is preferred to feed current and voltage directly into the power analyser. If an external current
transducer is required, no conventional current transformers shall be used. Instead, wide
bandwidth shunts or zero-flux transducers shall be used.
Fundamental voltage shall be measured at the motor terminals using a digital power analyser
equipped with suitable software (FFT, Fast Fourier Transformation).
Internal line filters in digital power meters shall be turned off. Synchronization filters (also known
as zero-cross filters) that are not in the signal path may be used.
For power measurement, the three-wattmeter method is preferred. All cables used to transmit
measurement signals shall be shielded. It has to be noted, that the cable shield is not routed
through the current transducers.
5.1.3 Mechanical output of the motor
The instrumentation used to measure supply frequency shall have an accuracy of ±0,1 % of full
scale. The speed measurement should be accurate within 0,1 revolution per minute for speeds
−1
up to 3 000 min and 0,03 % above.
The instrumentation used to measure the torque shall have a minimum class of 0,2 when the
rated efficiency is expected to be below 92 %, 0,1 below 95 %and 0,05 or better for higher
efficiencies. The minimum torque measured shall be at least 10 % of the torque measurement
device’s rated torque. If a better class instrument is used, the allowed torque range can be
extended accordingly.
5.2 Converter set-up
5.2.1 General
For all tests using the comparable converter, it should be parameterized according to the
requirements of this document or, if a unique combination of converter and motor is to be tested,
the converter should be parameterized according to the specific application requirements. The
chosen parameter settings shall be recorded in the test report.
5.2.2 Comparable converter set-up for rated voltages up to 1 kV
The comparable converter has to be understood as a voltage source independent of load
current.
It has to be noted, that the so-called comparable converter operating mode is not intended or
requested for any commercial application, but it is a typical set-up. The purpose of the
comparable converter set-up is to establish comparable test conditions for motors designed for
operation with commercially available converters.
The reference conditions defined below shall only be used for verification of compliance with
national energy efficiency regulations, in particular the 90 % speed and 100 % torque load point.
For all other purposes including the interpolation procedure according to Annex A preferably
the original system configuration should be used.
The following reference conditions are defined:
Two level voltage source converter.

– 12 – IEC 60034-2-3:2020 © IEC 2020
No additional components influencing output voltage or output current shall be installed
between the comparable converter and the motor, except those required for the measuring
instruments.
Operation at 90 % speed and rated torque with constant rated flux (approx. 90 % of rated
voltage) for both induction machines and synchronous machines.
NOTE The rated flux is defined by the rated voltage given on the name plate of the motor. Therefore, a
measurement at the 90 % speed and 100 % torque point with rated flux will be fully replicable for regulation
authorities.
−1
For motors with a rated speed up to 3 600 min , the switching frequency shall not be higher
than 5 kHz.
−1
For motors with a rated speed above 3 600 min , the switching frequency shall not be
higher than 10 kHz.
The conductor cross-sectional area of the motor cable should be selected such that the voltage
drop is not significant at rated load. An example for a typical test setup can be found in
IEC 61800-9-2:2017.
5.2.3 Testing with converters with rated voltages above 1 kV
For converters with voltage ratings above 1 kV a generally accepted comparable converter and
cable length cannot be specified. Such motors, cables and specific converters can only be
tested as a complete power drive system because the pulse patterns of frequency converters
for higher output powers vary between manufacturers and differ greatly between no-load and
rated load.
5.2.4 Testing with other converters
Motors that are operated with converters that produce a voltage with less harmonic content
than in case of supply by the comparable converter, for example multi-level converters or
converters with higher switching frequencies, will typically have lower losses compared with
measurements made with the comparable converter at 4 kHz or 8 kHz switching frequency.
Reference measurements on such motors shall still be performed under the reference
conditions as given above. Motor efficiency values measured under non-reference conditions
can be provided in the motor documentation.
6 Test method for the determination of the efficiency of converter-fed motors
6.1 Selection of determination method
For the verification of the rated losses and energy efficiency according to energy efficiency
classification schemes, the preferred method 6.2 according to Table 1 shall be applied.
The preferred method 2-3-A is mandatory for verification of rated efficiency declared by the
manufacturer. This verification may be required by end-users and regulators. For the
declaration process and the seven load points according to Annex A the manufacturer is free
to use other determination methods also.
Table 1 – Preferred test methods
Ref Method Description Subclause Required facility
2-3-A Direct-measurement Torque measurement 6.2 Torque meter or dynamometer
Input-output for full-load; Comparable or
specific converter supply
Alternate efficiency determining methods according to 6.3, 6.4 and 6.5 may be used for other
requirements, Table 2.
Table 2 – Other test methods
Ref Method Description Subclause Required facility
2-3-B Summation of losses Additional high 6.3 Sinusoidal supply and specific
frequency loss converter supply at no-load
determination with operation
converter for final
application
2-3-C Alternate Efficiency Calculation by qualified 6.4 Qualified base models and
Determination Method analytical model adequate calculation tool
(AEDM)
Determination of Calculation method for Pulse patterns of the specific
2-3-D 6.5
efficiency by calculation motors with rated converter system and adequate
output powers higher calculation tool
than 2 MW
6.2 Method 2-3-A – Direct measurement of input and output
6.2.1 Test set-up
This is a test method in which the mechanical power P of a machine is determined by
2C
measurement of the shaft torque and speed. The electrical power P of the stator is measured
1C
in the same test.
6.2.2 Test procedure
Tests shall be conducted with converter and an assembled motor with the essential components
in place, to obtain test conditions equal or very similar to normal operating conditions.
Check the offset of the torque measuring device and set it to zero as described in
IEC 60034-2-1:2014.
In case of permanent magnet machines, physically uncouple the motor under test, in order to
avoid residual torque in unexcited condition induced by permanent magnets.
Couple the motor under test to a load machine with a torque measuring device.
Operate the machine under test at rated torque and speed until thermal equilibrium (rate of
change of 1 K or less per half hour) has been reached.
At the end of the heat run, record:
T Output torque
C
n Speed
Motor input power
P
1C
Check the offset of the torque measuring device after stopping the machine. When measuring
several load points, the torque measuring device offset has to be checked only after the last
load point has been measured.
Correct the output torque T by the determined offset.
C
6.2.3 Efficiency determination
Calculate the output power:
P= 2π⋅⋅Tn
2C C
– 14 – IEC 60034-2-3:2020 © IEC 2020
Calculate the efficiency:
P
2C
η =
P
1C
In case differentiation between sinusoidal and converter supply losses is required, a
measurement on sinusoidal supply immediately followed (machine to be stopped in between)
by converter supply can be performed with equal fundamental voltages. This is only practical
for induction machines.
6.2.4 Measurement at seven standardized operating points
Apply the load to the machine at the seven standardized operating points given in Table 3.
The first load point for this test series shall be conducted after thermal equilibrium (rate of
change 1 K or less per half hour) has been reached.
The measurements of the subsequent standardized operating points (2, 3, 4, 5, 6 and 7) shall
be performed in quick succession to minimize temperature changes in the machine during
testing. Alternatively, the operating points can be measured in the order 4, 2, 5, 6, 3 and 7.
Each of the seven load points shall be set with an accuracy of ± 1 % of rated speed and ± 1 %
of rated torque before recording the motor input power.
NOTE Good lab practice takes at least 15 s for each load point.
Immediately after the seven standardized operating point measurements, check the offset of
the torque measuring device.
6.3 Method 2-3-B – Summation of losses with determination of additional high
frequency loss at converter supply at no-load operation
6.3.1 General
Experience has shown that the additional high frequency motor loss caused by voltage source
converter supply is in general basically independent of load. Therefore, the additional high
frequency loss caused by converter supply can be determined from a no-load-test at
fundamental frequency supply and a no-load-test at converter supply. The additional high
frequency loss is the difference of the measured losses of both tests.
NOTE This procedure is not applicable to all types of electrical machines.
6.3.2 Test set-up
A sinusoidal voltage source according to IEC 61000-2-4:2002, class 1, shall be available in
addition to the converter to perform these tests (nominally sinusoidal power supply).
The converter used for these tests is the specific converter intended for the final application.
6.3.3 Test procedure
The sequence of tests is as follows:
Perform a no-load test with sinusoidal power supply (frequency and voltage) of the
designated operation point according to IEC 60034-2-1:2014 for the determination of the
constant losses P .
Csin
Perform a no-load test with test-converter supply (frequency and voltage) of the designated
.
operation point for the determination of the constant losses P
Ccon
These measurements shall be performed immediately one after another.
The difference between the no-load losses for operation with the test-converter P and with
Ccon
a sinusoidal power supply P is the additional high frequency motor loss:
Csin
PP − P
LHL Ccon Csin
6.3.4 Efficiency determination
The additional high frequency motor loss P shall be added to the fundamental motor losses
LHL
as determined with a sinusoidal power supply according to IEC 60034-2-1:2014 in order to
obtain the motor efficiency under frequency converter operation.
The efficiency at converter supply is determined from:
P
2_60034-2-1
η=
PP+
1_60034-2-1 LHL
6.4 2-3-C – Alternate Efficiency Determination Method (AEDM)
This represents the calculation of the efficiency by the use of a tool sometimes referred to as
an analytical model. Multiple steps are required to qualify this model. Since the calculations are
influenced by manufacturing techniques each manufacturer will have to qualify their own
analytical model. Qualification requires the following conditions to be fulfilled:
Use of the recognized test procedure according to 6.2.
The test lab shall be qualified to reliably perform the tests with the required accuracy.
Enough different types or base models chosen to be tested and evaluated to prove the tool
is accurate across all products.
An adequate sample of each base model of an identical design shall be tested to verify that
the tool accurately predicts the nominal efficiency.
• All inputs are based on a statistical analysis that ensures their accuracy.
NOTE 1 Adequate in this context means at least 3 pieces per selected model.
The base models chosen should typically range in rated power, enclosure, speed, electrical
characteristics and other differing physical or functional characteristics which affect energy
consumption or efficiency.
NOTE 2 It is envisaged to develop the AEDM in future editions of this document to become an alternate preferred
method.
6.5 2-3-D – Determination of efficiency by calculation
In case of large motors with rated output powers higher than 2 MW, if the motor rating exceeds
the available testing capabilities, the determination of the additional high frequency losses
caused by converter operation based on calculations may be an alternative procedure to give
an order of magnitude of the additional losses. This calculation has to be based on the real
pulse patterns of the c
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