SIST-TS CLC IEC/TS 60034-31:2024

SLOVENSKI STANDARD
01-november-2024
Električni rotacijski stroji - 31. del: Izbiranje energijsko učinkovitih motorjev
vključno z motorji s spremenljivo hitrostjo - Smernice za uporabo (IEC/TS 60034-
31:2021)
Rotating electrical machines - Part 31: Selection of energye-fficient motors including
variable speed applications - Application guidelines (IEC/TS 60034-31:2021)
Drehende elektrische Maschinen - Teil 31: Auswahl von Energiesparmotoren
einschließlich Drehzahlstellantrieben - Anwendungsleitfaden (IEC/TS 60034-31:2021)
Machines électriques tournantes - Partie 31: Choix des moteurs écoénergétiques
incluant les applications à vitesse variable - Lignes directrices en matière d’application
(IEC/TS 60034-31:2021)
Ta slovenski standard je istoveten z: CLC IEC/TS 60034-31:2024
ICS:
29.160.30 Motorji Motors
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL SPECIFICATION CLC IEC/TS 60034-31

SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION January 2024
ICS 29.160.01 Supersedes CLC/TS 60034-31:2011
English Version
Rotating electrical machines - Part 31: Selection of energy-
efficient motors including variable speed applications -
Application guidelines
(IEC/TS 60034-31:2021)
Machines électriques tournantes - Partie 31: Choix des Drehende elektrische Maschinen - Teil 31: Auswahl von
moteurs écoénergétiques incluant les applications à vitesse Energiesparmotoren einschließlich Drehzahlstellantrieben -
variable - Lignes directrices en matière d'application Anwendungsleitfaden
(IEC/TS 60034-31:2021) (IEC/TS 60034-31:2021)
This Technical Specification was approved by CENELEC on 2024-01-03.

CENELEC members are required to announce the existence of this TS in the same way as for an EN and to make the TS available promptly
at national level in an appropriate form. It is permissible to keep conflicting national standards in force.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2024 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. CLC IEC/TS 60034-31:2024 E

European foreword
This document (CLC IEC/TS 60034-31:2024) consists of the text of IEC/TS 60034-31:2021 prepared
by IEC/TC 2 “Rotating machinery”.
This document supersedes CLC/TS 60034-31:2011.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Technical Specification IEC/TS 60034-31:2021 was approved by
CENELEC as a European Technical Specification without any modification.
In the official version, for Bibliography, the following notes have to be added for the standard
indicated:
IEC 60034-26 NOTE Approved as EN 60034-26
IEC/TS 60034-25 NOTE Approved as CLC/TS 60034-25
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod),
the relevant EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 60034-1 - Rotating electrical machines – Part 1: EN 60034-1 -
Rating and performance
IEC 60034-2-1 - Rotating electrical machines - Part 2–1: EN 60034-2-1 -
Standard methods for determining losses
and efficiency from tests (excluding
machines for traction vehicles)
IEC 60034-2-3 2020 Rotating electrical machines - Part 2–3: EN IEC 60034-2-3 2020
Specific test methods for determining
losses and efficiency of converter-fed AC
motors
IEC 60034-12 - Rotating electrical machines - Part 12: EN 60034-12 -
Starting performance of single-speed
three-phase cage induction motors
IEC 60034-30-1 - Rotating electrical machines - Part 30–1: EN 60034-30-1 -
Efficiency classes of line operated AC
motors (IE code)
IEC 60072 series Rotating electrical machines - Dimensions EN IEC 60072 series
and output series
IEC 61800-9-1 - Adjustable speed electrical power drive EN 61800-9-1 -
systems - Part 9–1: Ecodesign for power
drive systems, motor starters, power
electronics and their driven applications -
General requirements for setting energy
efficiency standards for power driven
equipment using the extended product
approach (EPA) and semi analytic model
(SAM)
A new edition is currently under preparation. Stage of this document at the time of publication: prEN IEC 60034.
Publication Year Title EN/HD Year
IEC 61800-9-2 2017 Adjustable speed electrical power drive EN 61800-9-2 2017
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
IEC/TS 60034-30-2 - Rotating electrical machines - Part 30–2: CLC IEC/TS 60034-30-2 -
Efficiency classes of variable speed AC
motors (IE-code)
IEC TS 60034-31 ®
Edition 2.0 2021-03
TECHNICAL
SPECIFICATION
colour
inside
Rotating electrical machines –

Part 31: Selection of energy-efficient motors including variable speed

applications – Application guidelines

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.160.01 ISBN 978-2-8322-9511-3

– 2 – IEC TS 60034-31:2021 © IEC 2021
CONTENTS
FOREWORD . 6
INTRODUCTION . 8
1 Scope . 9
2 Normative references . 9
3 Terms, definitions, symbols and acronyms . 10
3.1 Terms and definitions . 10
3.2 Symbols . 10
3.3 Acronyms . 10
4 Background . 11
4.1 General . 11
4.2 Introduction to IEC standards . 14
4.2.1 Overview . 14
4.2.2 Scope of efficiency classification . 16
4.2.3 Efficiency interpolation (IEC 60034-2-3) . 16
5 Applications . 18
5.1 Applications where the motor is fully loaded over longer periods of time . 18
5.2 Applications with square torque-speed characteristic (pumps, fans,
compressors) . 18
5.2.1 General . 18
5.2.2 Throttling versus variable speed control of pump systems . 19
5.2.3 On/off flow control of pump systems . 20
5.2.4 Pump systems for variable flow and their energy saving potential . 20
5.2.5 Summary for fan system design . 21
5.3 Applications with a constant torque characteristic (conveyors, lifts, hoist
drives) . 21
5.3.1 General . 21
5.3.2 Conveyors with constant speed versus variable speed control . 21
6 Fundamentals of electrical machines . 22
6.1 General . 22
6.2 Technology . 23
6.2.1 Technologies for fixed speed, line start motors . 23
6.2.2 Technologies for Variable Frequency Drive motors . 23
6.3 Efficiency . 23
6.3.1 General . 23
6.3.2 Motor losses . 25
6.3.3 Motors for higher efficiency classes . 25
6.3.4 Variations in motor losses . 26
6.4 Power factor . 26
6.5 Pole number, frequency and speed relations . 27
6.6 Differences between constant speed and variable speed operations . 27
7 Motors for constant speed operation . 28
7.1 General . 28
7.2 Motors rated for 50 Hz and 60 Hz . 28
7.3 Starting performance . 29
7.4 Operating speed and slip . 30
7.5 Motor losses for variable load . 30
7.6 Power factor . 31

IEC TS 60034-31:2021 © IEC 2021 – 3 –
7.7 Partial load efficiency . 32
7.8 Motors rated for different voltages or a voltage range . 33
7.9 Soft starters . 33
7.10 IE efficiency classes . 33
7.11 Efficiency testing methods . 33
7.12 Effects of power supply and ambient temperature variations . 34
7.12.1 Effects of power quality and variations in voltage and frequency . 34
7.12.2 Effects of voltage unbalance . 34
7.12.3 Effects of ambient temperature . 34
7.12.4 Voltages variations . 35
7.13 Motor dimensioning . 35
8 Motors for variable speed operation . 35
8.1 General . 35
8.2 Motors rated for arbitrary speeds . 36
8.3 Motor losses for variable frequency and load . 36
8.4 Further losses in motors designed for constant speed in variable speed
operation . 36
8.5 Variable frequency drives. 36
8.6 Variable frequency drive losses . 36
8.7 Variable frequency drive power factor . 37
8.8 Partial speed and partial torque efficiency of motor drive system . 38
8.9 IE and IES efficiency classes . 38
8.10 Efficiency determination methods . 38
8.11 Motor and variable frequency drive system dimensioning . 39
9 System selection guidelines . 40
9.1 Introduction to system selection methodology . 40
9.1.1 System design for minimal energy use . 40
9.1.2 Efficiency optimization potential of system versus components . 41
9.1.3 Selection criteria . 41
9.1.4 System with variable frequency drive . 42
9.2 Cost of electric motor systems . 43
9.2.1 Component costs . 43
9.2.2 Operating cost . 44
9.2.3 Life cycle cost . 44
10 Maintenance and lifetime expectations . 45
10.1 Common causes of failures in industrial motors . 45
10.2 Lifetime expectations of lubricants for bearings . 45
10.3 Lifetime expectations of insulations for windings . 45
10.4 Potential failure sources in bearings and insulation for motors supplied by VFD . 46
10.5 Variable frequency drive maintenance and expected lifetime. 46
10.6 Different categories of maintenance . 46
Annex A (informative) Typical efficiency values and losses of motors and variable
frequency drives . 48
A.1 General . 48
A.2 Losses of direct-on-line motors . 48
A.3 Losses of variable speed motors . 49
A.4 Losses of variable frequency drives (VFD) . 50
Annex B (informative) Tables of typical efficiency values of motors Direct-on-Line
(DOL) . 51

– 4 – IEC TS 60034-31:2021 © IEC 2021
Annex C (informative) Examples of energy savings and life cycle cost savings . 55
C.1 General . 55
C.2 Water pump . 55
C.3 Common interpretation error in fan applications when replacing motor . 58
C.4 Fans in parallel . 59
C.5 Electric motor materials versus energy efficiency and CO emissions . 60
Annex D (informative) Calculation sheet for losses and efficiency interpolation . 62
Bibliography . 63

Figure 1 – Industrial electric motors in numbers . 13
Figure 2 – Estimated global market shares of industrial electric motors per efficiency
class in the time period 1995 to 2020 . 14
Figure 3 – Components of a motor driven unit . 14
Figure 4 – Seven standardized operating points from IEC 60034-2-3 . 17
Figure 5 – Reduction of motor input power between one efficiency class to the next
higher class in percentage versus rated motor output power, shown cumulative for 4-
pole motors . 18
Figure 6 – System curves with and without a throttle valve and pump curves at
constant speeds . 20
Figure 7 – Average electric power consumption for end-suction own bearing (ESOB)
clean water pumps driven by different motors connected DOL or with VFD . 21
Figure 8 – System curves for conveyor (belt) drives, hoist drives, lifts, etc. . 22
Figure 9 – Squirrel cage induction motor . 23
Figure 10 – Operating capability for a DOL motor compared to a VFD motor. 28
Figure 11 – Typical 4-pole induction motor power loss distribution versus power rating . 31
Figure 12 – Performance characteristics of 4-pole, three phase, cage induction motors
of different power ratings . 32
Figure 13 – Typical variations of current, speed, power factor and efficiency with
voltage for constant output power . 35
Figure 14 – Schematic layout of a variable frequency drive . 37
Figure 15 – Distortion power factor versus the total harmonic distortion of the line
current at the input to a variable frequency drive. 38
Figure 16 – Typical system curves for different applications . 39
Figure 17 – Overview of a Motor Driven Unit and related equipment of a system . 40
Figure 18 – Relative cost of major components in an MDU, depending on rated power,

according to a European market survey in 2017/2018 . 43
Figure 19 – Distribution of failure causes for induction motors in industry . 45
Figure 20 – Simplistic representation in relative scale of three different maintenance
categories, namely corrective, preventive and predictive principles . 47
Figure C.1 – Standard water pump characteristic . 55
Figure C.2 – The torque versus synchronous speed for an induction motor of class IE2,
a line-started synchronous motor of class IE4 and the system curve of a fan,
respectively . 58
Figure C.3 – Comparison of two different fan control methods with equal flow . 59
Figure C.4 – Energy flow diagram from primary energy source, coal, to the electric
motor . 61
Figure D.1 – Extract from EXCEL calculation sheet available for download . 62

IEC TS 60034-31:2021 © IEC 2021 – 5 –

Table 1 – Overview of IEC standards on energy efficiency of power drive systems and
motor driven units . 16
Table 2 – Loss distribution in three phase, 4-pole, cage induction electric motors . 25
Table 3 – Relations between pole number, frequency and speed . 27
Table 4 – Exemplary efficiency calculation of a motor when operated at 50 Hz and
60 Hz with the same torque, using a 50 Hz motor rating as the basis . 29
Table 5 – IE efficiency classes of line operated AC motors . 34
Table B.1 – Typical efficiency values of 50 Hz IE1 induction motors . 51
Table B.2 – Typical efficiency values of 50 Hz IE2 induction motors . 52
Table B.3 – Typical efficiency values of 50 Hz IE3 induction motors . 53
Table B.4 – Typical efficiency values of 50 Hz IE4 induction motors . 54
Table C.1 – Calculation of motor performance at operating points 1 to 3 . 57
Table C.2 – System losses and performance . 57
Table C.3 – Calculated electricity, coal weight and CO emissions savings . 61
– 6 – IEC TS 60034-31:2021 © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ROTATING ELECTRICAL MACHINES –

Part 31: Selection of energy-efficient motors including
variable speed applications – Application guidelines

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,
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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.
The main task of IEC technical committees is to prepare International Standards. In exceptional
circumstances, a technical committee may propose the publication of a Technical Specification
when
• the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts, or
• the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical Specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC TS 60034-31, which is a Technical Specification, has been prepared by IEC technical
committee 2: Rotating machinery.

IEC TS 60034-31:2021 © IEC 2021 – 7 –
This publication contains an attached file titled, “TS 60034-31 Generic Efficiency Interpolation”,
in the form of an XLS document. This file is intended to be used as a complement and does not
form an integral part of this Technical Specifications.
This second edition cancels and replaces the first edition published in 2010. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) references to relevant standards have been updated;
b) global market data for industrial motors have been updated;
c) guidelines and theories about normal industrial applications have been described;
d) energy efficiency comparison examples have been given.
The text of this Technical Specificationis based on the following documents:
DTS Report on voting
2/2007/DTS 2/2028A/RVDTS
Full information on the voting for the approval of this Technical Specification 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 document 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.

– 8 – IEC TS 60034-31:2021 © IEC 2021
INTRODUCTION
This document gives technical and economical guidelines for the use of energy-efficient motors
in constant speed and variable speed operations in different applications.
About 50 % of the total global electric energy consumption is converted in electric motors, which
are the largest consumers of electricity per component type and industrial motors alone
accounting for around 30 % of all electricity in 2016. The wording ‘electricity consumption’ is
commonly used even though most of this energy is doing useful work. Electric motors convert
electric energy into mechanical energy where a minor part is converted into heat losses.
Therefore, electric motors, and especially motors operated with variable speed drives that
enable control of both speed and torque according to varying load requirements, are key
components that can achieve significant electricity savings.
A simple measure for reducing energy consumption is of course to invest in electric motors with
higher efficiency that normally result in rapid return on investments due to the dominating
operational costs through electricity bills. The highest energy saving potentials though can only
be identified by taking a holistic system perspective. It is estimated that only 12 % of the
installed base of electric motors are controlled by variable frequency drives, even though it is
estimated that more than 50 % of these motors would benefit by such control when for instance
wasteful mechanical control as throttling for varying the flow of a medium is replaced. This
document is intended to give guidance for proper use of constant speed motors and variable
speed motors and when to use them in light of actual applications and duty profiles.
Examples of constant torque duty profiles and quadratic torque duty profiles are given and
practical implications are described in order to facilitate enhanced understanding around viable
customs. Some parts of the document may be applicable for other motors as well.

IEC TS 60034-31:2021 © IEC 2021 – 9 –
ROTATING ELECTRICAL MACHINES –

Part 31: Selection of energy-efficient motors including
variable speed applications – Application guidelines

1 Scope
This part of IEC 60034 provides a guideline of technical and economical aspects for the
application of energy-efficient electric AC motors. It applies to motor manufacturers, OEMs
(original equipment manufacturers), end users, regulators, legislators and other interested
parties.
This document is applicable to all electrical machines covered by IEC 60034-1, IEC 60034-30-1
and IEC TS 60034-30-2.
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, Rotating electrical machines – Part 1: Rating and performance
IEC 60034-2-1, Rotating electrical machines – Part 2-1: Standard methods for determining
losses and efficiency from tests (excluding machines for traction vehicles)
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 60034-12, Rotating electrical machines – Part 12: Starting performance of single-speed
three-phase cage induction motors
IEC 60034-30-1, Rotating electrical machines – Part 30-1: Efficiency classes of line operated
AC motors (IE code)
IEC TS 60034-30-2, Rotating electrical machines – Part 30-2: Efficiency classes of variable
speed AC motors (IE-code)
IEC 60072 (all parts), Dimensions and output series for rotating electrical machines
IEC 61800-9-1, Adjustable speed electrical power drive systems – Part 9-1: Ecodesign for
power drive systems, motor starters, power electronics and their driven applications – General
requirements for setting energy efficiency standards for power driven equipment using the
extended product approach (EPA) and semi analytic model (SAM)
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

– 10 – IEC TS 60034-31:2021 © IEC 2021
3 Terms, definitions, symbols and acronyms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60034-1,
IEC 60034-30-1 and in IEC TS 60034-30-2 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
3.2 Symbols
∆p is the differential pressure, Pa
η is the hydraulic efficiency, per unit
hyd
η is the nominal efficiency, %
n
η is the rated efficiency, %
N
F is the drag force, N
f is the electrical frequency, Hz
e
f is the rated electrical frequency, Hz
N
I is the RMS current, A
–1
n is the actual speed, min
–1
n is the rated speed, min
N
–1
n is the maximum speed, min
max
–1
n is the synchronous speed, min
S
p is the number of poles
P is the motor output power, W
mot
P is the rated output power, W
N
Q is the flow rate, m /s
R is the resistance, Ω
s is the slip of an induction motor, %
T is the maximum output torque, Nm
max
T is the rated output torque, Nm
N
U is the rated voltage, V
N
v is the linear speed, m/s
3.3 Acronyms
AC alternating current
CDM complete drive module
DC direct current
DOL direct-on-line
EM electric motor
EP extended product
ESOB end-suction own bearing
IEC TS 60034-31:2021 © IEC 2021 – 11 –
GHG greenhouse gas
IE international energy efficiency of component index
IES international energy efficiency of system index
LSPM line-start permanent magnet synchronous motor
MDU motor driven unit
OEM original equipment manufacturer
OP operating point
PDS power drive system
PMSM permanent magnet synchronous motor
PWM pulse width modulation
ROI return on investment
RMS root-mean-square
RSM reluctance synchronous motor
TC technical committee
THD total harmonic distortion
VFD variable frequency drive
4 Background
4.1 General
This clause introduces the importance of energy efficiency and the high energy saving potential
related to the use of electric motors and variable frequency drives.
The global total amount of greenhouse gas emissions (GHG) was 49 gigatons (Gt) of CO
equivalents in 2010. The energy sector, which primarily involves electricity and heat production,
had the largest share of 35 % of the GHG emissions [1] . Coal was by far the largest energy
source for electricity production in 2015, with a share of 43 % of the total global generation of
20 000 TWh, followed by gas, hydro and nuclear with a share of 19 %, 15 % and 12 %,
respectively [2]. The average efficiency rate of coal power plants in 2017 was 33 % [3].
As mentioned in the introduction, about 50 % of the total global electric energy consumption is
converted by electric motors, which are the largest consumers of electricity per component type
[4-5]. Industrial motors alone accounted for around 30 % of all electricity consumption in 2016,
as seen in Figure 1a [4-6]. Another 20 % of electricity is consumed by electric motors in other
sectors like commercial, residential, transport and agriculture [6]. Therefore, electric motors
and especially motors operated by variable frequency drives (VFD) are key components for
achieving immense electricity savings. The installed base of industrial low voltage motors in the
power range between 0,12 kW and 1 000 kW is estimated to be more than 750 million units [7].
NOTE 1 The most part of the electric energy consumed by electric motors is converted into mechanical energy to
the driven equipment. The rest is converted into heat, that is losses. The expression “energy consumption” is used
in this document as an alternative to “energy conversion”, since it is a commonly used expression even though the
definition is according to the aforementioned sentence.
___________
Numbers in square brackets refer to the Bibliography.

– 12 – IEC TS 60034-31:2021 © IEC 2021
Currently, the share of motors equipped with electronic speed control is only about 12 % of the
installed motor base, as illustrated in Figure 1b [8]. It is estimated that it would be beneficial for
energy savings that this share should be more than 50 %. Replacing a direct on line motor with
a new motor with a higher efficiency class is a simple measure to improve energy efficiency in
most applications. However, a greater energy saving potential is associated with speed control,
when this can be used to replace less efficient mechanical control equipment like throttle valves
for pumps [9].
When taking life cycle costs into account, investments in energy saving measures can often
pay off within just a few years, or even months. The cost of electricity accounts for up to 96 %
of the total life cycle cost of a motor driven system, while the investment and installation costs
only account for around 2,5 % and maintenance costs account for the remaining 1,5 %, as
shown in Figure 1c [8]. Taking a holistic life cycle cost approach rather than a component price
optimization strategy can be highly profitable, when investing in motors and drives.
Pump systems presently account for more than 25 % of the worldwide electric energy
consumption in the industrial sector. It is estimated that around 40 % of this energy could be
saved. Centrifugal pumps in particular, accounting for a 73 % market share, represent great
potentials for energy savings, as some 75 % of these pumps are oversized [8]. Fan systems,
likewise centrifugal pumps, also have a load profile that rises quadratically with speed, resulting
in a cubic power profile with vast energy saving potentials when run with variable speed control.
These two applications alone account for 52 % of the low voltage industrial motor market [7].
The estimated global market shares of industrial electric motors per efficiency class in 2020 is
shown in Figure 1d [10], while their respective historic developments in the time period 1995 to
2020 are shown in Figure 2 [10-12]. The efficiency class with the highest share in 2020 was IE2
with around 41 % of the market. Likewise, 25 years earlier in 1995, IE0 (the class that applies
to motors with rated efficiencies below the minimum efficiency limits for the IE1 class) had the
largest share with around 56 % of the market. The IE4 class, currently the highest class for
direct on line operated motors, had a market share of around 2 % in 2020 [10], indicating that
the energy saving potential is still high.
NOTE 2 Widespread adoption of the IE4 class for direct-on-line motors is limited by the ability of motor
manufacturers to achieve this class for all motor ratings with the state of present technology.

IEC TS 60034-31:2021 © IEC 2021 – 13 –

a) Share of global electricity consumption per b) Share of constant speed or variable speed
component type control of installed global industrial electric motor
base
c) Share of life cycle costs components for d) Share of motor efficiency classes
industrial electric motors
Figure 1 – Industrial electric motors in numbers
The economical benefits by implementing energy saving measures on electric motor systems
and driven applications are more cost efficient than not doing the same investments. Therefore,
the main incentives for significant energy savings are already established, while the main
obstacles for their implantation are unawareness and purchase arrangements that commonly
are prioritizing initial product cost reductions over operational cost savings, which is vastly non-
profitable in a life cycle perspective, as is exemplified below.

– 14 – IEC TS 60034-31:2021 © IEC 2021

The IE0 class applies to motors with rated efficiencies below the efficiency limits for the IE1 class.
Figure 2 – Estimated global market
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