IEC TS 60034-25:2014

IEC TS 60034-25 ®
Edition 3.0 2014-10
TECHNICAL
SPECIFICATION
SPECIFICATION
TECHNIQUE
colour
inside
Rotating electrical machines –
Part 25: AC electrical machines used in power drive systems – Application guide

Machines électriques tournantes –
Partie 25: Machines électriques à courant alternatif utilisées dans les
entraînements électriques de puissance – Guide d'application

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IEC TS 60034-25 ®
Edition 3.0 2014-10
TECHNICAL
SPECIFICATION
SPECIFICATION
TECHNIQUE
colour
inside
Rotating electrical machines –

Part 25: AC electrical machines used in power drive systems – Application

guide
Machines électriques tournantes –

Partie 25: Machines électriques à courant alternatif utilisées dans les

entraînements électriques de puissance – Guide d'application

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
CODE PRIX XC
ICS 29.160 ISBN 978-2-8322-1876-1

– 2 – IEC TS 60034-25:2014 © IEC 2014
CONTENTS
FOREWORD . 8
INTRODUCTION . 10
1 Scope . 11
2 Normative references . 11
3 Terms and definitions . 12
4 System characteristics . 14
4.1 General . 14
4.2 System information . 14
4.3 Torque/speed considerations . 15
4.3.1 General . 15
4.3.2 Torque/speed capability . 15
4.3.3 Electrical machine rating. 16
4.3.4 Limiting factors on torque/speed capability . 16
4.3.5 Safe operating speed, over-speed capability and over-speed test . 16
4.3.6 Cooling arrangement . 17
4.3.7 Voltage/frequency characteristics . 17
4.3.8 Resonant speed bands . 18
4.3.9 Duty cycles . 18
4.4 Electrical machine requirements . 19
5 Losses and their effects (for induction electrical machines fed from voltage source
converters) . 21
5.1 General . 21
5.2 Location of the additional losses due to converter supply and ways to
reduce them . 22
5.3 Converter features to reduce the electrical machine losses . 23
5.3.1 Reduction of fundamental losses . 23
5.3.2 Reduction of additional losses due to converter supply . 23
5.4 Use of filters to reduce additional electrical machine losses due to converter
supply . 24
5.5 Temperature influence on life expectancy . 24
5.6 Determination of electrical machine efficiency . 25
6 Acoustic noise, vibration and torsional oscillation . 25
6.1 Acoustic noise . 25
6.1.1 General . 25
6.1.2 Changes in noise emission due to changes in speed . 25
6.1.3 Magnetically excited noise . 26
6.1.4 Sound power level determination and limits . 27
6.2 Vibration (excluding torsional oscillation) . 28
6.2.1 General . 28
6.2.2 Vibration level determination and limits . 28
6.3 Torsional oscillation . 29
7 Electrical machine insulation electrical stresses . 29
7.1 General . 29
7.2 Causes . 29
7.3 Winding electrical stress . 31
7.4 Limits and responsibility . 33

7.4.1 Electrical machines design for low voltage(≤ 1 000 V). 33
7.4.2 Electrical machines designed for medium and high voltage (> 1 000 V) . 34
7.5 Methods of reduction of voltage stress . 34
7.6 Insulation stress limitation . 35
8 Bearing currents . 36
8.1 Sources of bearing currents in converter-fed electrical machines . 36
8.1.1 General . 36
8.1.2 Magnetic asymmetry . 36
8.1.3 Electrostatic build-up . 36
8.1.4 High-frequency voltages . 36
8.2 Generation of high-frequency bearing currents . 36
8.2.1 General . 36
8.2.2 Circulating current . 37
8.2.3 Shaft earthing current . 37
8.2.4 Capacitive discharge current . 37
8.3 Common-mode circuit . 38
8.3.1 General . 38
8.3.2 System common-mode current flow . 38
8.4 Stray capacitances. 38
8.4.1 General . 38
8.4.2 Major component of capacitance . 39
8.4.3 Other capacitances . 39
8.5 Consequences of excessive bearing currents. 40
8.6 Preventing high-frequency bearing current damage . 40
8.6.1 Basic approaches . 40
8.6.2 Other preventive measures . 41
8.6.3 Other factors and features influencing the bearing currents . 42
8.7 Additional considerations for electrical machines fed by high voltage source
converters . 43
8.7.1 General . 43
8.7.2 Bearing protection of cage induction, brushless synchronous and
permanent magnet electrical machines . 43
8.7.3 Bearing protection for slip-ring electrical machines and for synchronous
electrical machines with brush excitation . 43
8.8 Bearing current protection for electrical machines fed by high-voltage current
source converters . 44
9 Installation . 44
9.1 Earthing, bonding and cabling . 44
9.1.1 General . 44
9.1.2 Earthing . 44
9.1.3 Bonding of electrical machines . 44
9.1.4 Electrical machine power cables for high switching frequency
converters . 45
9.2 Reactors and filters . 49
9.2.1 General . 49
9.2.2 Output reactors . 49
9.2.3 Voltage limiting filter (du/dt filter) . 49
9.2.4 Sinusoidal filter . 49
9.2.5 Electrical machine termination unit . 50
9.3 Power factor correction . 50

– 4 – IEC TS 60034-25:2014 © IEC 2014
9.4 Integral electrical machines (integrated electrical machine and drive modules)
............................................................................................................................. 51
10 Additional considerations for permanent magnet (PM) synchronous electrical
machines fed by voltage source converters . 51
10.1 System characteristics . 51
10.2 Losses and their effects . 51
10.3 Noise, vibration and torsional oscillation . 52
10.4 Electrical machine insulation electrical stresses . 52
10.5 Bearing currents . 52
10.6 Particular aspects of permanent magnets . 52
11 Additional considerations for cage induction electrical machines fed by high
voltage source converters . 52
11.1 General . 52
11.2 System characteristics . 53
11.3 Losses and their effects . 54
11.3.1 Additional losses in the stator and rotor winding . 54
11.3.2 Measurement of additional losses . 54
11.4 Noise, vibration and torsional oscillation . 54
11.5 Electrical machine insulation electrical stresses . 55
11.5.1 General . 55
11.5.2 Electrical machine terminal overvoltage . 55
11.5.3 Stator winding voltage stresses in converter applications. 55
11.6 Bearing currents . 57
12 Additional considerations for synchronous electrical machines fed by voltage
source converters . 57
12.1 System characteristics . 57
12.2 Losses and their effects . 57
12.3 Noise, vibration and torsional oscillation . 57
12.4 Electrical machine insulation electrical stresses . 57
12.5 Bearing currents . 57
13 Additional considerations for cage induction electrical machines fed by block-type
current source converters . 58
13.1 System characteristics (see Figures 30 and 31) . 58
13.2 Losses and their effects . 59
13.3 Noise, vibration and torsional oscillation . 61
13.4 Electrical machine insulation electrical stresses . 61
13.5 Bearing currents . 61
13.6 Additional considerations for six-phase cage induction electrical machines . 61
14 Additional considerations for synchronous electrical machines fed by LCI . 62
14.1 System characteristics . 62
14.2 Losses and their effects . 63
14.3 Noise, vibration and torsional oscillation . 63
14.4 Electrical machine insulation electrical stresses . 63
14.5 Bearing currents . 63
15 Additional considerations for cage induction electrical machines fed by pulsed
current source converters (PWM CSI) . 64
15.1 System characteristics (see Figure 34) . 64
15.2 Losses and their effects . 65
15.3 Noise, vibration and torsional oscillation . 65

15.4 Electrical machine insulation electrical stresses . 65
15.5 Bearing currents . 65
16 Wound rotor induction (asynchronous) electrical machines supplied by voltage
source converters in the rotor circuit . 65
16.1 System characteristics . 65
16.2 Losses and their effects . 65
16.3 Noise, vibration and torsional oscillation . 66
16.4 Electrical machine insulation electrical stresses . 66
16.5 Bearing currents . 66
17 Other electrical machine/converter systems . 66
17.1 Drives supplied by cyclo-converters . 66
17.2 Wound rotor induction (asynchronous) electrical machines supplied by
current source converters in the rotor circuit . 68
18 Special consideration for standard fixed-speed induction electrical machines in the
scope of IEC 60034-12 when fed from voltage source converter . 68
18.1 Torque derating during converter operation . 68
18.2 Losses and their effects . 70
18.3 Noise, vibrations and torsional oscillation . 70
18.4 Electrical machine insulation electrical stresses . 70
18.5 Bearing currents . 71
18.6 Maximum safe operating speed . 72
19 Additional considerations for synchronous reluctance electrical machine fed by
voltage source converters . 72
19.1 System characteristics . 72
19.2 Losses and their effects . 72
19.3 Noise, vibration and torsional oscillation . 72
19.4 Electrical machine insulation electrical stresses . 73
19.5 Bearing currents . 73
19.6 Particular aspects of synchronous reluctance electrical machines . 73
Annex A (informative) Converter characteristics . 74
A.1 Converter control types . 74
A.1.1 General . 74
A.1.2 Converter type considerations . 75
A.2 Converter output voltage generation (for voltage source converters) . 76
A.2.1 Pulse width modulation (PWM) . 76
A.2.2 Hysteresis (sliding mode) . 76
A.2.3 Influence of switching frequency . 76
A.2.4 Multi-level converters. 78
A.2.5 Parallel converter operation . 78
Annex B (informative) Output characteristics of 2 level voltage source converter
spectra . 79
Annex C (informative) Voltages to be expected at the power interface between
converter and electrical machine . 83

Figure 1 – Torque/speed capability . 15
Figure 2 – Converter output current . 16
Figure 3 – Examples of possible converter output voltage/frequency characteristics . 18

– 6 – IEC TS 60034-25:2014 © IEC 2014
Figure 4 – Example for the dependence of the electrical machine losses caused by
harmonics P related to the losses P at operating frequency f , on the switching
h, f1 1
frequency f in case of 2 level voltage source converter supply . 22
s
Figure 5 – Example of measured losses P as a function of frequency f and supply type . 23
L
Figure 6 – Additional losses ∆P of an electrical machine (same electrical machine as
L
Figure 5) due to converter supply, as a function of pulse frequency f , at 50 Hz
p
rotational frequency . 24
Figure 7 – Relative fan noise as a function of fan speed . 26
Figure 8 – Vibration modes of the stator core . 27
Figure 9 – Typical surges at the terminals of an electrical machine fed from a PWM
converter . 30
Figure 10 – Typical voltage surges on one phase at the converter and at the electrical
machine terminals (2 ms/division) . 31
Figure 11 – Individual short rise-time surge from Figure 10 (1 µs/division) . 31
Figure 12 – Definition of the rise-time t of the voltage pulse at the electrical machine
r
terminals . 32
Figure 13 – First turn voltage as a function of the rise-time . 33
Figure 14 – Discharge pulse occurring as a result of converter generated voltage surge
at electrical machine terminals (100 ns/division) . 35
Figure 15 – Possible bearing currents . 37
Figure 16 – Electrical machine capacitances . 39
Figure 17 – Bearing pitting due to electrical discharge (pit diameter 30 µm to 50 µm) . 40
Figure 18 – Fluting due to excessive bearing current . 40
Figure 19 – Bonding strap from electrical machine terminal box to electrical machine
frame . 45
Figure 20 – Examples of shielded electrical machine cables and connections . 46
Figure 21 – Parallel symmetrical cabling of high-power converter and electrical
machine . 47
Figure 22 – Converter connections with 360º HF cable glands showing the Faraday
cage . 47
Figure 23 – Electrical machine end termination with 360º connection . 48
Figure 24 – Cable shield connection . 48
Figure 25 – Characteristics of preventative measures . 50
Figure 26 – Schematic of typical three-level converter . 53
Figure 27 – Output voltage and current from typical three-level converter . 53
Figure 28 – Typical first turn voltage ∆U (as a percentage of the line-to-ground voltage)
as a function of du/dt . 55
Figure 29 – Medium-voltage and high-voltage form-wound coil insulating and voltage
stress control materials . 56
Figure 30 – Schematic of block-type current source converter . 58
Figure 31 – Current and voltage waveforms of block-type current source converter . 58
Figure 32 – Influence of converter supply on the losses of a cage induction electrical
machine (frame size 315 M, design N) with rated values of torque and speed . 60
Figure 33 – Schematic and voltage and current waveforms for a synchronous electrical
machine supplied from a current source converter . 62
Figure 34 – Schematic of pulsed current source converter . 64
Figure 35 – Voltages and currents of pulsed current source converter . 64

Figure 36 – Schematic of cyclo-converter . 66
Figure 37 – Voltage and current waveforms of a cyclo-converter . 67
Figure 38 – Fundamental voltage U as a function of operating frequency f . 69
1 1
Figure 39 – Torque derating factor for cage induction electrical machines of design N,
IC 0141 (self-circulating cooling) as a function of operating frequency f (example) . 70
Figure 40 – Limiting curve of admissible impulse voltage Û / U (peak value of line to
LL N
line voltage including voltage reflection and damping/rated voltage) at the electrical
machine terminals as a function of the rise-time t . 71
r
Figure A.1 – Effects of switching frequency on electrical machine and converter losses . 77
Figure A.2 – Effects of switching frequency on acoustic noise . 77
Figure A.3 – Effects of switching frequency on torque ripple . 78
Figure B.1 – Waveform of line-to-line voltage U for voltage source converter supply
LL
with switching frequency f = 30 × f (example) . 79
s 1
Figure B.2 – Typical frequency spectra of converter output voltage . 80
Figure B.3 – Typical frequency spectra of converter output voltage . 80
Figure B.4 – Typical spectra of converter output voltage . 81
Figure B.5 – Typical time characteristics of electrical machine current . 81
Figure B.6 – Typical time characteristics of electrical machine current . 82
Figure C.1 – Example of typical voltage curves and parameters of a two level inverter
versus time at the electrical machine terminals (phase to phase voltage; taken from
IEC TS 61800-8) . 83

Table 1 – Significant factors affecting torque/speed capability . 16
Table 2 – Electrical machine design considerations . 19
Table 3 – Electrical machine parameters for the tuning of the converter . 20
Table 4 – Operating voltage at the terminals in units of U where the electrical
N
machines may operate reliably without special agreements between manufacturers and
system integrators . 34
Table 5 – Effectiveness of bearing current countermeasures . 42

– 8 – IEC TS 60034-25:2014 © IEC 2014
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ROTATING ELECTRICAL MACHINES –

Part 25: AC electrical machines used in power drive systems –
Application guide
FOREWORD
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• 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 60034-25, which is a technical specification, has been prepared by IEC technical
committee 2: Rotating machinery.

This third edition of IEC TS 60034-25 cancels and replaces the second edition of IEC TS
60034-25, published in 2007, and the fourth edition of IEC TS 60034-17, published in 2006. It
constitutes a technical revision.
The main technical changes with regard to the previous editions of IEC TS 60034-25 and IEC
TS 60034-17 are as follows:
a) merging of IEC TS 60034-17 into IEC TS 60034-25 adding Clause 18 which now includes
all specific requirements for standard non-definite purpose electric machines. General
information and knowledge have been combined with the other Clauses of IEC TS 60034-
25;
b) replacement of “U Converter” with “voltage source converter”;
c) replacement of “I Converter” with “current source converter”;
d) redrafting of Clause 7;
e) addition of Subclause 9.2.6;
f) removal of Annex C: Noise increments due to converter supply.
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
2/1731/DTS 2/1750/RVC
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 publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
NOTE A table of cross-references of all IEC TC 2 publications can be found on the IEC TC 2 dashboard on the
IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• transformed into an International standard,
• 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.
– 10 – IEC TS 60034-25:2014 © IEC 2014
INTRODUCTION
The performance characteristics and operating data for converter-fed electrical machines are
influenced by the complete drive system, comprising supply system, converter, cabling,
electrical machine, mechanical shafting and control equipment. Each of these components
exists in numerous technical variants. Any values quoted in this technical specification are
thus indicative only.
In view of the complex technical interrelations within the system and the variety of operating
conditions, it is beyond the scope and object of this technical specification to specify
numerical or limiting values for all the quantities which are of importance for the design of the
power drive system.
To an increasing extent, it is the practice that power drive systems consist of components
produced by different manufacturers. The object of this technical specification is to explain, as
far as possible, the influence of these components on the design of the electrical machine and
its performance characteristics.
This technical specification deals with both
...