IEC 60034-2-2:2024

Rotating electrical machines - Part 2-2: Specific methods for determining separate losses of large machines from tests - Supplement to IEC 60034-2-1

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.

Machines électriques tournantes - Partie 2-2: Méthodes spécifiques pour déterminer les pertes séparées des machines de grande taille à partir d'essais - Complément à l'IEC 60034-2-1

L'IEC 60034-2-2:2024 s'applique aux machines électriques tournantes de grande taille et établit des méthodes supplémentaires pour la détermination des pertes séparées et qui sont destinées à définir un rendement, en complément de l'IEC 60034‑2‑1. Ces méthodes s'appliquent lorsqu'un essai à pleine charge n'est pas possible ou qu'il présente une plus grande incertitude. Les méthodes spécifiques décrites sont:
- la méthode de la machine étalonnée;
- la méthode du ralentissement;
- la méthode calorimétrique;
- la sommation des pertes pour les machines synchrones avec une excitation à aimants permanents.
Cette deuxième édition annule et remplace la première édition parue en 2010. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) alignement de la disposition et des procédures sur l'IEC 60034-2-1 et l'IEC 60034-2-3;
b) ajout de l'Annexe A: procédure informative pour la sommation des pertes des machines synchrones de grande taille avec une excitation à aimants permanents.

General Information

• Status: Published
• Publication Date: 11-Mar-2024
• ICS: 29.160.01 - Rotating machinery in general
• Technical Committee: TC 2 - Rotating machinery
• Drafting Committee: WG 28 - TC 2/WG 28
• Current Stage: PPUB - Publication issued
• Start Date: 12-Mar-2024
• Completion Date: 01-Mar-2024

Relations

• Revises: IEC 60034-2-2:2010 - Rotating electrical machines - Part 2-2: Specific methods for determining separate losses of large machines from tests - Supplement to IEC 60034-2-1
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC 60034-2-2 ®
Edition 2.0 2024-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Rotating electrical machines –
Part 2-2: Specific methods for determining separate losses of large machines
from tests – Supplement to IEC 60034-2-1

Machines électriques tournantes –
Partie 2-2: Méthodes spécifiques pour déterminer les pertes séparées des
machines de grande taille à partir d'essais – Complément à l'IEC 60034-2-1
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IEC 60034-2-2 ®
Edition 2.0 2024-03
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Rotating electrical machines –

Part 2-2: Specific methods for determining separate losses of large machines

from tests – Supplement to IEC 60034-2-1

Machines électriques tournantes –

Partie 2-2: Méthodes spécifiques pour déterminer les pertes séparées des

machines de grande taille à partir d'essais – Complément à l'IEC 60034-2-1

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.160.01  ISBN 978-2-8322-8171-0

– 2 – IEC 60034-2-2:2024 © IEC 2024
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Symbols and abbreviated terms . 7
4.1 Symbols . 7
4.2 Additional subscripts . 8
5 Basic requirements . 8
5.1 Direct and indirect efficiency determination . 8
5.1.1 General . 8
5.1.2 Direct . 8
5.1.3 Indirect . 8
5.2 Uncertainty . 9
6 Additional test methods for the determination of the efficiency of large machines . 9
6.1 General . 9
6.1.1 Overview . 9
6.1.2 Efficiency . 10
6.1.3 Total loss . 10
6.2 Method 2-2-A – Calibrated machine . 11
6.2.1 General . 11
6.2.2 Test procedure . 12
6.2.3 Direct efficiency determination . 12
6.2.4 Determination of separate losses . 13
6.3 Method 2-2-B – Retardation method. 13
6.3.1 General . 13
6.3.2 Test procedure . 15
6.3.3 Determination of deceleration and retardation constant . 17
6.3.4 Determination of separate losses . 19
6.4 Method 2-2-C – Calorimetric method . 20
6.4.1 General . 20
6.4.2 Calorimetric instrumentation . 22
6.4.3 Test procedure . 25
6.4.4 Determination of losses . 26
Annex A (informative) Summation of losses for permanent-magnet synchronous
machines . 30
A.1 General . 30
A.2 No-load test with magnetized rotor . 30
A.3 No-load test with unmagnetized rotor . 30
A.4 Iron losses . 31
A.5 Test with rotor removed . 31
A.6 Rated stator winding losses and additional load losses . 32
A.7 Total losses . 33
Bibliography . 34

Figure 1 – Efficiency determination according to method 2-2-A . 11
Figure 2 – Efficiency determination according to method 2-2-B . 14

Figure 3 – Method of the chord . 17
Figure 4 – Efficiency determination according to method 2-2-C . 21
Figure 5 – Reference surface . 22
Figure 6 – Four coolers connected in parallel, single calorimeter, single coolant . 23
Figure 7 – Series connected coolers, two coolants . 24
Figure 8 – Bypass piping . 24
Figure 9 – Parallel piping . 25
Figure 10 – Characteristics of pure water as a function of temperature . 27

Table 1 – Additional methods for large machines . 9

– 4 – IEC 60034-2-2:2024 © IEC 2024
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ROTATING ELECTRICAL MACHINES –

Part 2-2: Specific methods for determining
separate losses of large machines from tests –
Supplement to IEC 60034-2-1
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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9) IEC draws attention to the possibility that the implementation of this document may involve the use of (a)
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shall not be held responsible for identifying any or all such patent rights.
IEC 60034-2-2 has been prepared by IEC technical committee 2: Rotating machinery. It is an
International Standard.
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) Layout and procedures aligned with IEC 60034-2-1 and IEC 60034-2-3.
b) Annex A added: an informative procedure for the summation of losses for large permanent-
magnet excited synchronous machines.

The text of this International Standard is based on the following documents:
Draft Report on voting
2/2157/FDIS 2/2178/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
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 webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
– 6 – IEC 60034-2-2:2024 © IEC 2024
ROTATING ELECTRICAL MACHINES –

Part 2-2: Specific methods for determining
separate losses of large machines from tests –
Supplement to IEC 60034-2-1
1 Scope
This part of IEC 60034 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.
NOTE In situ testing according to the calorimetric method for full-load conditions is recognized.
The specific methods described are:
– Calibrated-machine method.
– Retardation method.
– Calorimetric method.
– Summation of losses for permanent magnet excited synchronous machines.
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)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60034-1 and
IEC 60034-2-1 apply, as well as the following.
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
calibrated machine
machine whose mechanical power input/output is determined, with low uncertainty, using
measured electrical output/input values according to a defined test procedure

3.2
calibrated-machine method
method in which the mechanical input/output to/from an electrical machine under test is
determined from the measurement of the electrical input/output of a calibrated machine
mechanically coupled to the test machine
3.3
retardation method
method in which the separate losses in a machine under test are deduced from the
measurements of the deceleration rate of its rotating components when only these losses are
present
3.4
calorimetric method
method in which the losses in a machine are deduced from the measurements of the heat
generated by them
3.5
thermal equilibrium
state reached when the temperature rises of the several parts of the machine do not vary by
more than rate of change 1 K per half hour
[SOURCE: IEC 60050-411:1996, 411-51-08]
4 Symbols and abbreviated terms
4.1 Symbols
A is an area, m ,
2 2
C is the retardation constant, kg m s ,
c is the specific heat capacity of the cooling medium, J/(kg K),
p
h is the coefficient of heat transfer, W/(m K),
J is the moment of inertia, kg m ,
–1
n is the operating speed, s ,
P is the input power, W,
P is the excitation power supplied by a separate source, W,
1E
P is the output power, W,
P is the I R armature-winding losses (interpole, compensation and series field winding
a
loss in case of DC machines), W,
P is the brush losses, W,
b
P is the constant losses, W,
c
P is the excitation circuit losses, W,
e
P is the exciter losses, W,
Ed
P is the electrical power, excluding excitation, W,
el
P is the excitation (field winding) losses, W,
f
P is the iron losses, W,
fe
is the friction and windage losses, W,
P
fw
P is the short-circuit losses, W,
sc
– 8 – IEC 60034-2-2:2024 © IEC 2024
P is the additional load losses, W,
LL
P is the mechanical power, W,
mech
P is the I R rotor winding losses, W,
r
P is the stator I R winding losses, W,
s
is the total losses, W,
P
T
Q is the volume rate of flow of the cooling medium, m /s,
t is the time, s,
v is the exit velocity of cooling medium, m/s,
Δp is the difference between the static pressure in the intake nozzle and ambient
pressure, N/m ,
Δθ is the temperature rise of the cooling medium, or the temperature difference between
the machine reference surface and the external ambient temperature, K,
δ is the per unit deviation of rotational speed from rated speed,
ρ is the density of the cooling medium, kg/m ,
θ is the temperature, °C.
4.2 Additional subscripts
c for the cooling circuit,
E for exciter,
ers for outside reference surface,
i for inner voltage,
irs for inside reference surface,
rs for the reference surface,
RR for test with rotor removed,
t test,
0 no-load,
1 input,
2 output.
5 Basic requirements
5.1 Direct and indirect efficiency determination
5.1.1 General
Tests can be grouped in the following categories.
5.1.2 Direct
Input-output measurements on a single machine are considered to be direct. This involves the
measurement of electrical or mechanical power into, and mechanical or electrical power out of
a machine.
5.1.3 Indirect
Measurements of the separate losses in a machine under a particular condition are considered
to be indirect. This is not usually the total loss but comprises certain loss components. The
method may, however, be used to calculate the total loss or to calculate a loss component.

The determination of total loss shall be carried out by one of the following methods:
– direct measurement of total losses;
– summation of separate losses.
NOTE The methods for determining the efficiency of machines are based on a number of assumptions. Therefore,
it is not possible to make a comparison between the values of efficiency obtained by different methods.
5.2 Uncertainty
Uncertainty as used in this document is the uncertainty of determining a true efficiency. It
reflects variations in the test procedure and the test equipment.
Although uncertainty should be expressed as a numerical value, such a requirement needs
sufficient testing to determine representative and comparative values.
6 Additional test methods for the determination of the efficiency of large
machines
6.1 General
6.1.1 Overview
For the determination of performance when machine load and/or size exceed test capabilities
(described in IEC 60034-2-1), the following test methods may be used. See Table 1.
Table 1 – Additional methods for large machines
Reference Method Description Subclause Application Required facility
2-2-A Calibrated Loss 6.2 All types of Calibrated
machine measurement via machines machine
calibrated
machine
2-2-B Retardation Loss 6.3 Applicable for
method measurement by factory and on-site
retardation measurements
2-2-C Calorimetric Loss 6.4 Applicable for
method measurement in factory and on-site
the primary and measurements
secondary coolant
NOTE These methods are generally applicable to large machines where the facility cost for other methods is not
economical.
Losses relative to machine load (with lowest uncertainty) are best determined from actual
measurements. For example: measurements of current, resistance, etc., under full-load
operation.
When this is not possible, these values shall be obtained from calculation of the parameters
during the design stage.
Determination of losses not itemized in this part may be found in IEC 60034-2-1.

– 10 – IEC 60034-2-2:2024 © IEC 2024
6.1.2 Efficiency
Efficiency is:
PP+ − P P
1 1E T 2
η
PP++P P
1 1E 2 T
where
P is the input power excluding excitation power from a separate source;
P is the output power;
P is the excitation power supplied by a separate source;
1E
P is the total loss.
T
NOTE 1 Input power P and output power P are as follows:
1 2
in motor operation: P = P ; P = P ;
1 el 2 mech
= P ; P = P .
in generator operation: P
1 mech 2 el
NOTE 2 P includes the excitation circuit losses P of the machine where applicable.
T e
6.1.3 Total loss
When the total loss is determined as the sum of the separate losses the following formulae
apply:
For direct current machines:
P = P + P + P + P + P
T c a b LL e
P = P + P
e f Ed
P = P + P
c fw fe
For induction machines:
P = P + P + P + P
T c s r LL
P = P + P
c fw fe
For synchronous machines:
P = P + P + P + P
T c s LL e
P = P + P + P
e f Ed b
P = P + P
c fw fe
==
6.2 Method 2-2-A – Calibrated machine
6.2.1 General
The calibrated machine method may be used to determine the test machine efficiency either
directly or by separate losses.
For an overview, Figure 1 provides a flowchart for efficiency determination by this test method.

Figure 1 – Efficiency determination according to method 2-2-A
This method is generally applied as a factory test.
The tested machine shall be equipped with winding ETDs.
The tested machine shall be completely assembled with essential components as for normal
operation.
This method requires a calibrated machine mechanically coupled to the machine under test and
is used when a torque meter is not available. The mechanical input of the tested machine is
calculated from the electrical input of the calibrated machine.
When a gear-box is directly connected to the machine it shall be considered as part of the
calibrated machine.
Calibrate an electric machine, preferably a direct-current machine, according to one of the
procedures in IEC 60034-2-1 at a sufficient number of thermally stable loads (including no-load)
to determine an accurate relationship of output power as a function of input power adjusted for
the temperature of the cooling air/medium at inlet. This is generally developed in the form of a
curve.
It is generally advisable to take several readings of all instruments at each load-point during
short periods of time and average the results to obtain a more accurate test value.

– 12 – IEC 60034-2-2:2024 © IEC 2024
6.2.2 Test procedure
Before starting the test, record the winding resistances and the ambient temperature.
The machine for which the performance is to be determined shall be mechanically coupled to
the calibrated machine and be operated at a speed equivalent to its synchronous/rated speed.
Operate the calibrated machine with the test machine at either rated-load, partial-load; no-load
not excited, with or without brushes; no-load excited at rated voltage; or short-circuited, which
enables specific categories of losses to be determined.
When the test machine is operated at each specified test condition and has reached thermal
stability, record:
– for the calibrated machine
P = input power
U = input voltage
I = current
θ = temperature of inlet cooling air
1c
θ = winding temperature (by variation of resistance if possible)
1w
n = speed
– for the test machine (direct determination as a generator)
P = output power
U = output voltage or armature voltage (when excited open-circuit)
I = armature load current
θ = windings temperature (either directly by ETDs or by resistance variation)
2w
n = speed.
Upon completion of each test, stop the machines and record in the given order:
– test machine winding resistance;
– calibrated machine winding resistance.
NOTE The example represents testing with a motor as the calibrated machine.
Finally operate the calibrated machine without electrical connection to the test machine and
record as specified above.
From the curve developed in 6.2.1 and using the calibrated machine input values, select the
appropriate output power to the test machine.
Adjust the output power for the standardized coolant temperature.
Determination of excitation power shall be in accordance with IEC 60034-2-1.
6.2.3 Direct efficiency determination
When the test machine is operated with rated conditions, the test machine efficiency is:
P
η= test machine working as a generator, calibrated machine working as a motor
P
where
P is the output power of test generator;
P is the calculated input power to the test generator;
and:
P
η= test machine working as a motor, calibrated machine working as a generator
P
where
P is the input power to test motor;
P is the calculated output power from the test motor.
6.2.4 Determination of separate losses
Using values of P determined from the calibrated machine curve, it is possible to determine the
power dissipated by the test machine for other selected conditions that may be used to
determine efficiency according to 6.1.2.
a) Friction and windage losses at rated speed (when the test machine is not electrically
connected);
b) Active iron losses, and additional open-circuit losses in DC and synchronous machines,
(when tested at no-load, open-circuit, excited at rated voltage, minus the windage and
friction loss). Field losses from a separate source;
c) Stator winding losses and additional load losses in synchronous machines, (when tested
under short-circuit conditions, excited at rated armature current, minus the windage and
friction loss). Field losses from a separate source.
6.3 Method 2-2-B – Retardation method
6.3.1 General
The retardation method can be used in determining the separate losses of rotating electrical
machines having an appreciable rotational inertia.
The retardation method is used to determine:
– sum of the friction and windage losses ("mechanical losses") in machines of all types;
– sum of losses in active iron and additional open-circuit losses in DC and synchronous
machines;
– sum of I R losses in an operating winding and additional load losses ("short-circuit losses")
in synchronous machines.
For an overview, Figure 2 provides a flowchart for efficiency determination by this test method.

– 14 – IEC 60034-2-2:2024 © IEC 2024

Figure 2 – Efficiency determination according to method 2-2-B
The recorded test loss P which retards the machine is proportional to the product of the speed
t
to which this loss corresponds and the deceleration at that speed:
dn
Pn=−C× ×
t
dt
where:
P is the loss being measured;
t
C is the retardation constant;
n is the speed;
dn/dt is the deceleration.
NOTE 1 The accuracy of the retardation method is directly related to the accuracy of the retardation constant C
which depends solely on the moment of inertia J.
The test machine shall be assembled, with all essential components, as for normal operation,
but uncoupled from other rotating parts. A suitable speed sensor shall be attached to the
rotating element.
When the machine cannot be uncoupled, all possible steps should be taken to reduce the
mechanical losses in other rotating parts, e.g. by partial dismantling or in the case of a water

turbine, by preventing water in the runner chamber. Rotation of the runner in air produces a
windage loss which should be determined either experimentally or from calculations.
NOTE 2 The test machine may be driven by its normal prime mover, e.g. by Pelton turbine when the water supply
to the runner can be cut off instantly.
Excitation from a mechanically-coupled exciter is not recommended, but may be permitted when
the value of the deviation of speed δ does not exceed 0,05. Losses in exciters coupled to the
shaft of the test machine shall be taken into account.
The bearing temperatures shall be adjusted to the rated design temperature of the bearings, by
adjusting the coolant flow.
The primary coolant temperature shall be adjusted, whenever possible, to the rated primary
coolant temperature at which the windage loss measurement is required by throttling the
secondary coolant flow.
If agreed between customer and supplier, losses in common bearings should be stated
separately, whether such bearings are supplied with the machine or not.
The losses in bearings and thrust bearings shall be subtracted from the total sum of the
mechanical losses. If the tested machine uses direct-flow cooling (external coolant directly
supplied to the bearing by piping) of the bearings, these losses are distributed between the
tested machine and any other coupled to it mechanically, such as turbine, in proportion to the
masses of their rotating parts. If there is no direct-flow cooling, the distribution of bearing losses
shall be determined from empirical formulae. Retardation tests shall be conducted as a series
without interruption, whenever possible. It is recommended that the series start and finish with
retardation tests of the test machine unexcited.
All tests shall be repeated several times at the preset rated values of open-circuit voltage or
short-circuit current. The arithmetic mean value obtained from each series of measurements
shall be assumed to be the appropriate loss value of that category of loss.
Select a value of δ (the per unit deviation of rotational speed from rated speed) which shall not
be greater than 0,1 and may have to be less than this, depending on the characteristics of the
machine.
6.3.2 Test procedure
Electrically connect the test machine as a motor (on no-load) fed from a separate power source
having a wide range of variable frequency. Any excitation shall be obtained from a separate
source with a rapid and precise voltage control.
Rapidly accelerate the test machine to a speed above n (1 + δ). Disconnect the machine from
N
its supply source. Sufficient time delay shall separate the switching off of the supply and starting
the measurements to allow electromagnetic transients to decay.
During deceleration to n (1 – δ) place the test machine in the required condition, according to
N
the following tests:
Usual test sequence to determine separate losses when the inertia is either known or if
unknown, to be followed after determination according to one of the tests 4 to 7:
Test 1: running unexcited;
Test 2: running open-circuited, excited at rated voltage;
Test 3: running with the armature terminals short-circuited, and the excitation set to give the
rated armature current.
– 16 – IEC 60034-2-2:2024 © IEC 2024
As an alternate, tests may be carried out at various values within limits of the order of 95 % to
105 % of either the rated voltage or rated short-circuit current.
Additional tests, when the moment of inertia is unknown, shall be conducted at the same values
as determined in test 2 and test 3 according to either test 4, test 5, test 6 or test 7.
Test 4: running as an unloaded motor;
Test 5: running unexcited, connect the test machine to a transformer previously set under no-
load condition and excite to the preset values of open-circuit voltage;
Test 6: running unexcited, connect the test machine to a transformer previously set under
short-circuit and excite to the preset values of current;
Test 7: running unexcited, simultaneously load the exciter or the auxiliary generator with a
ballast resistance at a predetermined load.
Each retardation test shall be repeated at least twice.
Measurements of voltage and current shall be taken at the instant when the test machine passes
through rated speed, except in the case of an unexcited retardation test.
Excitation circuit power shall be measured, if excitation is not provided by a separate source.
The measured values of open-circuit voltage or short-circuit current shall not differ from the
preset values by more than ± 2 %. The calculated final value of the speed derivative in time for
each of the tests shall be adjusted proportionally by the ratio of the square of the preset value
to the measured value.
Highly accurate recording instruments shall be used either with continuous or with discrete
recording of test values of speed and time.
(1 + δ)
For each test category, take sufficient measurements to accurately locate the points n
N
and n (1 – δ) as a function of time.
N
For all tests, record:
n as a function of t;
θ = winding temperatures (either directly or by resistance variation);
w
θ = inlet/outlet temperature of the primary cooling medium.
a
For the following tests record additionally:
When running open-circuited, excited at rated voltage (Test 2):
P during initial operation before retardation at rated voltage;
U open-circuit rated voltage.
For synchronous machines, when running with the stator terminals short-circuited (Test 3):
I armature current.
a
For the additional tests, when the moment of inertia is unknown, record additionally
(Tests 4 to 7):
P input power of the unloaded motor, that is equal to the sum of the mechanical loss P
4 fw
and iron loss P (the armature circuit I R loss is ignored);
fe
P transformer no-load loss;
U open-circuit rated voltage;
P transformer short-circuit loss;
I armature current;
a
P exciter or auxiliary generator load.
6.3.3 Determination of deceleration and retardation constant
6.3.3.1 General
This chord method requires the measurement of the time interval (t – t ) during which the
2 1
speed of the tested machine changes from n (1 + δ) to n (1 – δ), see Figure 3. The ratio of
N N
speed interval 2 δ n to (t – t ) is approximately the deceleration at rated speed:
N 2 1
2δn dn
N
≈−
nn=
t − t dt
N
where
δ is the per unit deviation of rotational speed from rated speed.

Figure 3 – Method of the chord
Determine the deceleration for the required tests and record as:
dn
t
dt
where:
t is the number of the test according to 6.3.2.
NOTE According to the definition dn/dt is a negative value.
6.3.3.2 Known moment of inertia
When the moment of inertia of a machine’s rotating part has been previously determined by
either measurement (preferred) or by design calculation, the retardation constant is calculated
from:
– 18 – IEC 60034-2-2:2024 © IEC 2024
C = 4π × J
where:
J is the moment of inertia.
6.3.3.3 Unknown moment of inertia
6.3.3.3.1 General
In case of an unknown inertia one of the tests 4 to 7 shall be performed to determine the inertia.
6.3.3.3.2 Test 4 – Operation as an unloaded motor
When the test machine is operated as an unloaded motor, the input power is equal to the sum
of the mechanical loss P and iron loss P (the armature circuit I R loss is ignored), then the
fw fe
retardation constant C is determined from the formula:
PP+
fw fe
C=−
dn
n × 4
N
dt
6.3.3.3.3 Test 5 – Retarded by open-circuited transformer
When the test machine is retarded by the transformer open-circuit loss, with the ohmic I R loss
according to the transformer open-circuit current ignored, then:
dn
P+ P+=P −Cn× × 5
fw fe 5 N
dt
hence
P
C= −
dn dn
n 54−

N
dt dt

6.3.3.3.4 Test 6 – Retarded by short-circuited transformer
When the test machine is retarded by the transformer short-circuit loss, with the iron loss
corresponding to magnetic flux in the short-circuited transformer ignored, then
𝑑𝑑𝑛𝑛
𝑃𝑃 +𝑃𝑃 +𝑃𝑃 =−𝐶𝐶 ×𝑛𝑛 × � 6
fw sc 6 N
𝑑𝑑𝑑𝑑
hence
P
C=−
dn dn
n 63−

N
dt dt

6.3.3.3.5 Test 7 – Retardation by exciter or auxiliary generator
When the test machine is retarded by the exciter or auxiliary generator loaded with a ballast
resistance, the retardation losses consist only of the test machine mechanical loss P and the
fw
measured load P (with allowance for efficiency of the exciter or auxiliary generator which can
be determined by calculations). Then:
dn
P +=P −Cn 7
fw 7 N
dt
hence
P
C=−
dn dn
n 71−

N
dt dt

6.3.4 Determination of separate losses
6.3.4.1 General
The tested loss P which retards the machine is:
t
dn
P=−Cn × t
tN
dt
where:
n is rated speed,
N
P is tested loss,
t
C is retardation constant;
dn
t is the deceleration from test t, where t is the specific test number according to 6.3.2.
dt
6.3.4.2 Friction and windage losses
The friction and windage (mechanical) loss P of the test machine are:
fw
dn
P =−Cn × 1
fw N
dt
6.3.4.3 Iron losses
The iron loss P is:
fe
dn
P =−×Cn × 2− P
fe N fw
dt
Excitation should be provided by a separate source.

– 20 – IEC 60034-2-2:2024 © IEC 2024
6.3.4.4 Short-circuit losses
The short-circuit loss P is:
k
dn
Pn=−×C3× − P
sc N fw
dt
Excitation should be provided by a separate source.
6.3.4.5 Separation of additional and short-circuit losses
The sum of the I R loss and the additional loss in the armature circuit is determined as the
difference of losses measured in the third and first test. Separation of this sum into components,
if required, is done by subtracting from it the I R loss in the armature circuit calculated from the
armature circuit resistance corresponding to the test temperature.
Losses evaluated according to above mentioned procedures, may be used to determine total
machine losses and efficiency according to 6.1.2.
6.4 Method 2-2-C – Calorimetric method
6.4.1 General
The calorimetric method may be used to determine the efficiency of large electrical rotating
machinery:
a) either by the determination of the total loss on load, or
b) by the determination of the separate losses.
In the calorimetric method losses are determined from the product of the amount of coolant and
its temperature rise, and the heat dissipated in the surrounding media.
For an overview, Fig
...