EN 60034-4:1995

SLOVENSKI STANDARD
01-april-1999
Rotating electrical machines - Part 4: Methods for determining synchronous
machine quantities from tests (IEC 60034-4:1985 (Modified))
Rotating electrical machines -- Part 4: Methods for determining synchronous machine
quantities from tests
Drehende elektrische Maschinen -- Teil 4: Verfahren zur Ermittlung der Kenngrößen von
Synchronmaschinen durch Messungen
Machines électriques tournantes -- Partie 4: Méthodes pour la détermination à partir
d'essais des grandeurs des machines synchrones
Ta slovenski standard je istoveten z: EN 60034-4:1995
ICS:
29.160.01 Rotacijski stroji na splošno Rotating machinery in
general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

NORME CEI
INTERNATIONALE IEC
34-4
INTERNATIONAL
Deuxième édition
STAN DARD
Second edition
Machines électriques tournantes
Partie 4:
Méthodes pour la détermination à partir d'essais
des grandeurs des machines synchrones
Rotating electrical machines
Part 4:
Methods for determining synchronous machine
quantities from tests
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34-4 ©IEC 1985 — 3 —
CONTENTS
Page
FOREWORD
PREFACE
SECTION ONE — SCOPE AND OBJECT
Clause
1. Scope
Object 15
2.
SECTION TWO — GENERAL
3. General
SECTION THREE — TERMINOLOGY AND METHODS OF DETERMINATION
4. Direct-axis synchronous reactance Xd 19
5. Short-circuit ratio Kc 19
6. Quadrature -axis synchronous reactance Xq
7. Direct-axis transient reactance Xd'
8. Direct-axis subtransient reactance Xd
Quadrature-axis subtransient reactance 21
9.
10. Negative-sequence reactance X2 23
11. Negative-sequence resistance R2
12. Zero-sequence reactance X0
Zero-sequence resistance Ro 23
13.
14. Potier reactance Xp 25
Armature and excitation winding direct-current resistance Ra and Rf 25
15.
16. Positive-sequence armature winding resistance R I
17. Direct-axis transient open-circuit time constant Tao
Ta 25
18. Direct-axis transient short-circuit time constant

19. Direct-axis subtransient short-circuit time constant T'd'
20. Armature short-circuit time constant Ta 27
21. Acceleration time T J
22. Stored energy constant H
23. Rated excitation current If
n
24. Rated voltage regulation Un
SECTION FOUR — DESCRIPTION OF THE TESTS AND DETERMINATION
OF MACHINE QUANTITIES FROM THESE TESTS

25. No-load saturation test 29

26. Sustained three-phase short-circuit test 31
27. Determination of quantities from the no-load saturation and sustained three-phase short-

circuit characteristics
Overexcitation test at zero power-factor 33
28.
29. Determination of the excitation current corresponding to the rated voltage and rated armature

current at zero power-factor (overexcitation) 35
30. Determination of Potier reactance from the no-load and sustained three-phase short-circuit
characteristics and the excitation current corresponding to the rated voltage and rated arma-

ture current at zero power-factor (overexcited) 37

1985 - 5 -
34-4 © IEC
31. Determination of the rated excitation current by the Potier diagram 37
32. Determination of the rated excitation current by the ASA diagram 41
33. Determination of the rated excitation current by the Swedish diagram 43
34. Negative excitation test 45
35. Determination of Xq from the negative excitation test 45
36. Low slip test 45
37. Determination of Xq from the low slip test
38. On-load test measuring the load angle 8
39. Determination of Xq from the on-load test measuring the load angle
40. Sudden three-phase short-circuit test
Determination of quantities from the sudden three-phase short-circuit test 57
41.
42. Voltage recovery test 59
43. Determination of quantities from the voltage recovery test 61
44. Applied voltage test with the rotor in direct and quadrature axis positions with respect to the
armature winding field axis 61
45. Determination of quantities from the applied voltage test with the rotor in direct and
axis positions with respect to the armature winding field axis 63
quadrature
46. Applied voltage test with the rotor in any arbitrary position 63
47. Determination of quantities from the applied voltage test with the rotor in any arbitrary
position 65
48. Line-to-line sustained short-circuit test 65
49. Determination of quantities from the line-to-line sustained short-circuit test 67
50. Negative-phase sequence test 67
51. Determination of quantities from the negative-phase sequence test 69
52. Single-phase voltage application to the three-phase test 69
53. Determination of quantities from the single-phase voltage application to the three-phase
test
Line-to-line and to neutral sustained short-circuit test 71
54.
55. Determination of quantities from the line-to-line and to neutral sustained short-circuit test
56. Direct-current winding resistance measurements by the voltmeter and ammeter method and
by the bridge method
57. Determination of winding d.c. resistance from the direct-current winding resistance measure-
ments by the voltmeter and ammeter and by the b ridge methods
58. Field current decay test with the armature winding open-circuited 75
59. Determination of tid o from the field current decay test with the armature winding open-
circuited
60. Field current decay test with the armature winding short-circuited
Determination of t d' from the field current decay test with the armature winding short-
61.
circuited 77
62. Suspended rotor oscillation test 77
63. Determination of ti and H from suspended rotor oscillation test
64. Auxiliary pendulum swing test 79
65. Determination of tiJ and H from the auxiliary pendulum swing test  79
66. No-load retardation test 79
Determination of t and H
67. from the no-load retardation test 81
68. On-load retardation test of mechanically coupled machines with the synchronous machine
operating as a motor 81
34-4 © I EC 1985 - 7 -
of mechanically coupled machines from the on-load retardation
69. Determination of Tj and H
81 test with the synchronous machine operating as a motor
Acceleration after a load drop test with the machine operating as a generator
70.
of mechanically coupled machines from the acceleration after a
71. Determination of TJ and H
83 load drop test with the machine operating as a generator
72. Determination of quantities by calculations using known test quantities
TABLE I
A - Unconfirmed test methods for determining synchronous machine quantities
APPENDIX
from tests
A 1. Scope
A2. Object
91 A3. General
TERMINOLOGY AND METHODS OF EXPERIMENTAL STUDY
fk) 93
A4. Excitation current corresponding to the rated armature short-circuit current (i
A5. Direct-axis synchronous reactance Xd
Xq
A6. Quadrature-axis synchronous reactance
d' A7. Direct-axis transient reactance X
Quadrature-axis transient reactance XQ A8.
Quadrature-axis subtransient reactance Xq A9.
A10. Negative-sequence reactance X2
A11. Armature-leakage reactance X,
Al2. Initial starting impedance of synchronous motors 4
Direct-axis transient open-circuit time constant Tao A13.
T a 97
A14. Direct-axis transient short-circuit time const ant
A15. Quadrature-axis transient open-circuit time constant Tgo
T A16. Quadrature-axis transient short-circuit time constant
ant T a q
A17. Direct-axis subtransient open-circuit time const
-axis subtransient open-circuit time const ant
A18. Quadrature
r 0
A19. Quadrature-axis subtransient short-circuit time constant T
A20. Direct-axis open-circuit excitation winding time constant Tfdo
A21. Direct-axis open-circuit equivalent damper circuit time constant
Tkdo
Tfd -A22. Direct-axis short-circuit excitation winding time constant
Tkd 101
Direct-axis short-circuit equivalent damper winding time constant
A23.
A24. Frequency response characteristics
DESCRIPTION OF THE TESTS AND DETERMINATION OF QUANTITIES AND
CHARACTERISTICS FROM THESE TESTS
Over-excitation test at zero power factor and va riable armature voltage
A25.
A26. Determination of the excitation current corresponding to the rated armature sustained
short-circuit current (ifk)
A27. Phase shifting test
105 A28. Determination of quantities from the phase shifting test
Disconnecting applied low armature voltage at a very low-slip test
A29.
A30. Determination of quantities from the disconnecting applied low armature voltage at a very
low-slip test
Disconnecting applied low armature voltage test, the machine running asynchronously on
A31.
load
34-4©IEC1985 - 9 -
A32. Determination of quantities from the sudden disconnection of applied low armature vol-
tage, the machine running asynchronously on load, test 111
A33.
Sudden short-circuiting of machine, running on load at low-voltage, test 113
A34. Determination of quantities from sudden short-circuiting, running on load at low voltage
test 113
A35. Sudden line-to-line short-circuit test 115
A36. Determination of negative-sequence reactance from the sudden line-to-line short-circuit
test 115
A37. Suddenly applied short-circuit test following disconnection from line 117
A38. Determination of quantities from the suddenly applied short-circuit test following
disconnection from line 117
A39. Applied voltage test with rotor removed 117
A40. Determination of quantities from the applied voltage test 117
A41.
Locked rotor test 119
A42. Determination of initial starting impedance from the locked rotor test 121
A43. Suddenly applied excitation test with armature winding open-circuited 121
A44. Determination of Tdo from the suddenly applied excitation test with armature winding
open-circuited 123
A45. Suddenly applied excitation test with armature winding short-circuited 123
A46. Determination of Td from suddenly applied excitation test with armature winding
short-circuited 123
A47. Voltage recovery test 123
A48. Determination of quantities from the voltage recovery test 125
A49. Field extinguishing test with armature winding open-circuited 125
A50. Determination of quantities from the field extinguishing test with armature winding open-
circuited 125
A51. Field extinguishing test with armature winding short-circuited 129
A52. Determination of quantities from the field extinguishing test with armature winding short-
circuited 129
A53. Asynchronous operation on-load test 129
A54. Determination of frequency response characteristics and quantities from the asynchronous
operation on-load test 131
A55. Asynchronous operation during the low-voltage test 133
A56. Determination of the frequency response characteristics and quantities from the
asynchronous low-voltage operation test 133
Applied vari A57. able frequency voltage test at standstill 135
A58. Determination of the frequency response characteristics and quantities from the applied
variable frequency voltage test at standstill 135
A59. D.C. decay in the armature winding at standstill test 139
A60. Determination of frequency response characteristics and quantities from the d.c. decay
test 141
A61. Suddenly applied d.c. at standstill test 147
A62. Determination of frequency response characteristics from the suddenly applied d.c. at
standstill test 151
A63. Determination of quantities by calculation using known test quantities 153
TABLE IA 155
REFERENCE LIST 161
FIGURES A 1 TO A23 164
- 11 - 34-4 © IEC 1985
INTERNATIONAL ELECTROTECHNICAL COMMISSION
ROTATING ELECTRICAL MACHINES
Part 4: Methods for determining synchronous machine quantities from tests
FOREWORD
The formal decisions or agreements of the I E C on technical matters, prepared by Technical Committees on which all the National
1)
Committees having a special interest therein are represented, express, as nearly as possible, an international consensus of opinion
on the subjects dealt with.
They have the form of recommendations for international use and they are accepted by the National Committees in that
2)
sense.
ational unification, the IEC expresses the wish that all National Committees should adopt the text of
3) In order to promote inte rn
the I E C recommendation for their national rules in so far as national conditions will permit. Any divergence between the I E C
the corresponding national rules should, as far as possible, be clearly indicated in the latter.
recommendation and
PREFACE
This standard has been prepared by Sub-Committee 2G: Test Methods and Procedures, of I EC Technical Committee No. 2:
Rotating Machinery.
This second edition replaces the first edition of I EC Publication 34-4 (1967) — incorporating Amendment No. 1(1973) — and the
first edition of I EC Publication 34-4A (1972), first supplement.
In addition, this new edition includes some editorial changes.
rts being:
This standard forms Pa rt 4 of a series of publications dealing with rotating electrical machinery, the other pa
Part 1: Rating and Performance, issued as I EC Publication 34-1 (1983).
Part 2: Methods for Determining Losses and Efficiency of Rotating Electrical Machinery from Tests (excluding Machines for
Traction Vehicles), issued as I EC Publication 34-2 (1972).
Part 3: Ratings and Characteristics of Three-phase, 50 Hz Turbine-type Machines, issued as I EC Publication 34-3 (1968).
5: Classification of Degrees of Protection provided by Enclosures for Rotating Machines, issued as I EC Publication 34-5
Part
(1981).
6: Methods of Cooling Rotating Machinery, issued as I EC Publication 34-6 (1969).
Part
gements of Rotating Electrical Machinery, issued as
Part 7: Symbols for Types of Construction and Mounting Arr an
I E C Publication 34-7 (1972).
8: Terminal Markings and Direction of Rotation of Rotating Machines, issued as I E C Publication 34-8 (1972).
Part
Part 9: Noise Limits, issued as I EC Publication 34-9 (1972).
10: Conventions for Desc ription of Synchronous Machines, issued as I EC Publication 34-10 (1975).
Part
Part 11: Built-in Thermal Protection, Chapter I : Rules for Protection of Rotating Electrical Machines, issued as
I EC Publication 34-11 (1978).
12: Starting Performance of Single-speed Three-phase Cage Induction Motors for Voltages up to and Including 660 V, issued
Part
as I EC Publication 34-12 (1980).
Part 13: Specification for Mill Auxiliary Motors, issued as IEC Publication 34-13 (1980).
Part 14: Mechanical Vibration of Certain Machines with Shaft Heights 56 mm and Higher — Measurement, Evaluation and Limits
of the Vibration Severity, issued as I EC Publication 34-14 (1982).

34-4 © IEC 1985 - 13 -
The text of this standard is based on the following documents:
Six Months' Rule Report on Voting
2G(CO)4 2G(CO)6
2G(CO)12
2G(CO)8
2G(CO)18 2G(CO)19
Further information can be found in the Reports on Voting indicated in the table above.
The following IEC publication is quoted in this standard:
Publication No. 51 (—): Direct Acting Indicating Analogue Electrical Measuring Instruments and their Accessories.

34-4 © I EC 1985 — 15 —
ROTATING ELECTRICAL MACHINES
Part 4: Methods for determining synchronous machine quantities from tests
SECTION ONE — SCOPE AND OBJECT
Scope
1.
This standard applies to three-phase synchronous machines of 1 kVA rating and larger with rated
frequency of not more than 400 Hz and not less than 15 Hz.
The test methods are not intended to apply to special synchronous machines such as permanent-
magnet field machines, inductor type machines, etc.
While the tests also apply in general to brushless machines, certain va riations do exist and special
precautions should be taken.
2. Object
The object of this standard is to establish methods for determining characteristic quantities of
three-phase synchronous machines from tests.
It is not intended that this standard should be interpreted as requiring the carrying out of any or
all of the tests described therein on any given machine. The particular tests to be carried out shall be
subject to a special agreement.
SECTION TWO — GENERAL
3. General
Tests for determining synchronous machine quantities should be conducted on a completely
sound machine, all the devices for automatic regulation being switched off.
Unless otherwise stated, the tests are conducted at the rated speed of rotation.
3.1 Indicating measuring instruments and their accessories, such as measuring transformers, shunts and
bridges used during tests, unless otherwise stated, should have an accuracy class not above 1.0
(I EC Publication 51: Direct Acting Indicating Analogue Electrical Measuring Instruments and
their Accessories). The instruments used for determining d.c. resistances should have an accuracy
class not above 0.5.
It is not intended at this stage to specify an accuracy class for the oscillographic measuring
equipment. This should, however, be chosen, having due regard to the rated frequency of the
machine to be tested, so that the readings are taken in a linear portion of the vibrator amplitude
against frequency characteristic.
The measurement of the speed of rotation, of synchronous machines may be conducted by means
of a stroboscopic method or by using tachometers (mechanical or electrical).

34-4 ©I E C 1985 — 17 —
Instead of measuring the speed of rotation, it is permissible to measure frequency by means of a
frequency meter when the machine is running synchronously with any other machine or running on
its own.
3.2 The temperature of the windings is measured in those tests when the quantities to be determined
depend on it or when knowledge of it is required by the safety considerations of the machine during
tests.
In cases where transient temperatures might exceed the safe values, it is recommended that the
tests be started only after the machine has been run at no-load with normal cooling or has been at
rest for a period to ensure low starting temperature, and the temperatures should be carefully
monitored or pre-determined so that the test may be discontinued before the temperature becomes
excessive.
3.3 During the test, the machine winding connection, as a rule, should be as for normal working.
The determination of all quantities is made considering star connection of the armature winding
(unless special connections such as open delta are specified). If the armature winding is actually
delta connected, the values of the quantities obtained in accordance with this standard correspond
to an equivalent star connected winding.
3.4 All the quantities and characteristics should be designated in per unit values considering rated
values of the voltage
(Un), and the apparent power (Sn) as basic ones. In this case basic current
will be:
Sn
In =
11TUn
and basic impedance:
U2
(
_
Sn
Z = ,Sn I 312n S2
n
The intermediate calculations, if it is convenient, may be performed in physical values with
subsequent conversion to the quantity in per unit value. It is recommended to express time in
seconds. In the calculations of characteristics, and when drawing diagrams, excitation current
corresponding to the rated voltage on the no-load curve is taken as the basic value of the excitation
current.
If a machine has several rated values, those taken for the basic values should be stated.
Unless otherwise stated, the above-mentioned system is accepted in this standard. Small letters
designate the quantities in per unit values, and capital letters designate them in physical
quantities.
3.5 In the formulae given in this standard for determining synchronous machine reactances, the positive
sequence armature resistance, unless otherwise stated, is considered to be negligible.
When the positive sequence armature resistance constitutes more than 0.2 of the measured
reactance, the formulae must be considered as approximate.
3.6 The definitions of the majority of quantities and their experimental methods of determination, as
given in this standard, correspond to the widely accepted two-axis theory of synchronous machines
with approximate representation of all circuits additional to the field winding, and stationary
circuits relative to it, by two equivalent circuits, one along the direct axis and the other along the
quadrature axis, neglecting armature resistance or taking it into consideration only approxi-
mately.
34-4 © I EC 1985 — 19 —
As a consequence of this approximate machine representation, three reactances (synchronous,
transient and sub-transient) and two time constants (transient and sub-transient) are considered in
this standard for transient phenomena studies along the direct axis, two reactances (synchronous
and sub-transient) and one time constant (sub-transient) along the quadrature axis, and the
armature short-circuit time constant.
These time constants are based on the assumption of an exponential decrease of the particular
components of quantities involved (currents, voltages, etc.). If the plot of the measured component
under consideration does not decrease as a pure exponential, as in the case, for example, of a solid
rotor machine, the time constant should normally be interpreted as the time required for the
component to decrease to 1/e 0.368 of its initial value. Exponential decay curves corresponding
to these time constants should be considered as equivalent curves replacing the actual measured
ones.
3.7 Synchronous machine quantities vary with saturation of the magnetic circuits. In practical calcula-
tions both saturated and unsaturated values are used.
In this standard, unless otherwise stated, the "saturated value" of reactances and resistances will
be taken as the rated (armature) voltage value of the quantity, and their "unsaturated value" will be
taken as the rated (armature) current value, except synchronous reactance which is not defined as
saturated.
The rated (armature) voltage value of a quantity corresponds to the magnetic condition of the
machine during sudden short circuit of the armature winding from no-load rated voltage operation,
the machine running at rated speed.
The rated (armature) current value of a quantity corresponds to the condition in which the
fundamental a.c. component of armature current which determines this particular quantity is equal
to the rated current.
SECTION THREE — TERMINOLOGY AND METHODS OF DETERMINATION
4. Direct-axis synchronous reactance Xd
The quotient of the sustained value of that fundamental a.c. component of armature voltage
which is produced by the total direct-axis armature flux due to direct-axis armature current, and the
value of the fundamental a.c. component of this current, the machine running at rated speed.
4.1 The direct-axis synchronous reactance Xd corresponding to the unsaturated state is determined (see
Clause 27) from the no-load saturation (see Sub-clause 25.1) and sustained three-phase short circuit
(see Sub-clause 26.1) characteristics.
5. Short-circuit ratio K,
The ratio of the field current for rated armature voltage on open-circuit to the field current for
rated armature current on sustained symmetrical short circuit, both with the machine running at
rated speed.
5.1 The short-circuit ratio is determined (see Sub-clause 27.1) from the no-load saturation (see Sub-
clause 25.1) and sustained three-phase sho rt circuit (see Sub-clause 26.1) characteristics.
6. Quadrature-axis synchronous reactance Xq
The quotient of the sustained value of that fundamental a.c. component of armature voltage
armature flux due to quadrature axis armature
which is produced by the total quadrature -axis
current, and the value of the fundamental a.c. component of this current, the machine running at
rated speed.
— 21 —
34-4 © I EC 1985
6.1 Quadrature-axis synchronous reactance is determined by the following methods:
a) negative excitation (see Clauses 34 and 35);
b) low slip (sec Clauses 36 and 37);
c) on load measurement of the load angle (see Clauses 38 and 39).
The first two methods are preferred.
7. Direct-axis transient reactance Xd
The quotient of the initial value of a sudden change in that fundamental a.c. component of
flux, and the value of the
armature voltage which is produced by the total direct-axis armature
simultaneous change in fundamental a.c. component of direct-axis armature current, the machine
running at rated speed and the high decrement components during the first cycles being
excluded.
7.1 Direct-axis transient reactance is determined by the following methods:
rt circuit (see Clauses 40 and 41);
a) sudden three-phase sho
voltage recovery (see Clauses 42 and 43);
b)
d (see Clause 18) by
calculation from the test values of Xd (see Clause 4), (see Clause 17) and T
c)
T
the formula given in Clause 72.
The method of the sudden three-phase short circuit is preferred. It permits saturated and
unsaturated values of Xd to be determined.
8. Direct-axis subtransient reactance Xa
The quotient of the initial value of a sudden change in that fundamental a.c. component of
armature voltage which is produced by the total direct-axis armature flux, and the value of the
simultaneous change in fundamental a.c. component of direct-axis armature current, the machine
running at rated speed.
8.1 Direct-axis subtransient reactance is determined by the following methods:
a) sudden three-phase short circuit (see Clause 40 and Sub-clause 41.1);
b) voltage recovery (see Clause 42 and Sub-clause 43.1);
c) applied voltage with the rotor in the direct and quadrature axis positions with respect to the
armature winding field axis (see Clauses 44 and 45);
d) applied voltage with an arbitrary position of the pole axis (see Clauses 46 and 47).
rt circuit method is preferred. It permits saturated and unsaturated
The sudden three-phase sho
values of Xa to be determined.
The applied-voltage methods (c and d) may be used for the unsaturated value of Xa, but are
usually not practicable for the saturated value because of the large current required and possible
overheating of solid pa rts.
9. Quadrature-axis subtransient reactance Xq
quotient of the initial value of a sudden change in that fundamental a.c. component of
The
quadrature-axis armature flux, and the value of the
armature voltage which is produced by the total
quadrature-axis armature current, the
simultaneous change in fundamental a.c. component of
machine running at rated speed.

34-4 © I E C 1985 — 23 —
9.1 The quadrature axis subtransient reactance is determined by the following methods:
a) applied voltage with the rotor in the direct and quadrature axis positions with respect to the
armature winding field axis (see Clause 44 and Sub-clause 45.1);
b)
applied voltage with the pole axis in any arbitrary position (see Clause 46 and Sub-
clause 47.1).
Both these methods are practically equivalent and may be used to determine the unsaturated
value. These methods are usually not practicable for the determination of the saturated value
because of the large current required and possible overheating of solid parts.
10. Negative-sequence reactance X2
The quotient of the reactive fundamental component of negative-sequence armature voltage due
to sinusoidal negative-sequence armature current of rated frequency, and the value of this current,
the machine running at rated speed.
Note. — A different value might be obtained for this reactance if the fundamental component of a current, which also
however, is the one determined with sinusoidal current.
contains harmonics, is used. The correct value of X2,
11. Negative-sequence resistance R2
The quotient of the in-phase fundamental component of negative-sequence armature voltage,
due to sinusoidal negative-sequence armarture current of rated frequency, and the value of this
current, the machine running at rated speed.
Note. — A different value might be obtained for this resistance if the fundamental component of a current, which also
contains harmonics, is used.
11.1 Negative-sequence reactance and resistance are determined by the following methods:
a) line-to-line sustained sho rt circuit (see Clauses 48 and 49 and Sub-clause 49.1);
b) negative-phase sequence (see Clauses 50 and 51);
c) negative-sequence reactance may also be determined by calculation from the test values of Xd
(see Clause 8) and XQ (see Clause 9); the calculation is made using the equation given in Sub-
clause 72.1.
The line-to-line sustained short-circuit method is preferred.
12. Zero-sequence reactance X0
The quotient of the reactive fundamental component of a zero-sequence armature voltage, due to
the presence of fundamental zero-sequence armature current of rated frequency, and this
component of current, the machine running at rated speed.
13. Zero-sequence resistance Ro
The quotient of the in-phase fundamental component of zero-sequence armature voltage, due to
the presence of fundamental zero-sequence armature current of rated frequency, and the value of
this current, the machine running at rated speed.
13.1 Zero-sequence reactance and resistance are determined by the following methods:
a) single-phase voltage application to the three-phases connected in series (an open delta) or
parallel (see Clauses 52 and 53);
b)
line-to-line and to neutral sustained short-circuit (see Clauses 54 and 55 and Sub-
clause 55.1).
— 25 —
34-4 ©IEC 1985
The method of single-phase voltage application to the three phases connected in series is
preferred.
Potier reactance Xp
14.
An equivalent reactance used in place of the armature leakage reactance to calculate the excita-
tion on load by means of the Potier method. It takes into account the additional leakage of the field
winding on load and in the overexcited region and is greater than the real value of the armature
leakage reactance.
Potier reactance is determined in accordance with Clause 30.
14.1 The
current resistance R a and Rf
Armature and excitation winding direct -
15.
Direct-current winding resistance is determined by the following methods:
voltmeter and ammeter (see Clauses 56 and 57);
a)
ridge (see Clause 56 and Sub-clause 57.1).
b) single and double b
The single bridge method is not permissible for measuring resistances less than 1 SZ.
R1
16. Positive-sequence armature winding resistance
The quotient of the in-phase component of positive sequence armature voltage corresponding to
direct-load losses in the armature winding and stray load losses in conductors, due to the sinusoidal
positive sequence armature current, and of this current, the machine running at rated speed.
16.1 The positive-sequence armature winding resistance is determined in accordance with Sub-
clause 72.2.
Direct-axis transient open -circuit time constant
17.
-cd'o
The time required for the slowly changing component of the open-circuit armature voltage which
is due to the direct-axis flux, following a sudden change in operating conditions, to decrease to
1/e 0.368 of its initial value, the machine running at rated speed.
17.1 The direct-axis transient open-circuit time constant is determined by the following methods:
field current decay with open-circuit armature winding (see Clauses 58 and 59);
a)
voltage recovery (see Clause 42 and Sub-clause 43.2);
b)
(see Clause 4), Xd (see Clause 7) and Td (see Clause 18)
c) calculation from the test values of Xd
by the formula given in Clause 72.
The field current decay method is preferred.
short-circuit time constant Td
18. Direct-axis transient
The time required for the slowly changing component of direct-axis short-circuit armature
z
0.368 of its initial
current following a sudden change in operating conditions, to decrease to 1/e
value, the machine running at rated speed.
18.1 The direct-axis transient sho rt circuit time constant is determined by the following methods:
circuit (see Clause 40 and Sub-clause 41.2);
a) sudden three-phase sho rt
34-4 © I EC 1985 — 27 —
b) field current decay with armature winding short-circuited (see Clauses 60 and 61);
(see Clause 17)
c) calculation from the test values of Xd (see Clause 4), Xa (see Clause 7) and Ta o
by the formula given in Clause 72.
Xa, then -r d' should be determined from
If a sudden short-circuit test is performed for determining
the same test. In all other cases preference is given to the field current decay method with the
armature winding short-circuited.
circuit time constant 'c 'd'
19. Direct-axis subtransient short -
The time required for the rapidly changing component, present during the first few cycles in the
direct-axis short-circuit armature current, following a sudden change in operating conditions, to
decrease to 1/E 0.368 of its initial value, the machine running at rated speed.
19.1 The direct-axis subtransient short-circuit time constant is determined by the sudden three-phase
short-circuit method (see Clause 40 and Sub-clause 41.3).
20. Armature short-circuit time constant
Ta
The time required for the aperiodic d.c. component present in the short-circuit armature current,
following a sudden change in operating conditions, to decrease to 1/e 0.368 of its initial value, the
machine running at rated speed.
20.1 The armature short-circuit time constant is determined from the sudden three-phase short-circuit
test by the following methods:
by decrease of the periodic (a.c.) component in the excitation winding current (see Clause 40 and
a)
Sub-clause 41.4);
by decrease of the aperiodic (d.c.) components of the current in the armature winding phases
b)
(see Clause 40 and Sub-clause 41.5);
X2 (see Clause 10) and R a (see Clause 15) by the formula given
c) calculation from the test values of
in Sub-clause 72.3.
The method of measurement of the decrease of periodic component in the excitation winding
current is preferred.
21. Acceleration time 'r1
s of the synchronous machine from rest to rated speed,
The time required to bring rotating part
the accelerating torque being constant and equal to the quotient of the rated active power (output)
and of the rated angular velocity.
For synchronous condensers, the rated active power (output) is replaced by the rated apparent power.
Notes 1. —
When the acceleration time is determined for a group of mechanically coupled machines, the accelerating torque
2. —
is calculated for rated active power and rated angular velocity of the base synchronous machine.
22. Stored energy constant H
The quotient of the kinetic energy stored in the rotor when running at rated speed and of the rated
apparent power.
22.1 The acceleration time of a machine or group of machines and the stored energy constant are
determined by the following methods:
a) suspended rotor oscillation (see Clauses 62 and 63);

— 29' —
34-4 © I EC 1985
auxiliary pendulum swing (see Clauses 64 and 65);
b)
c) no-load retardation (see Clauses 66 and 67);
on-load retardation with the machine operating as a motor (see Clauses 68 and 69);
d)
acceleration after sudden unloading with the machine operating as a generator (see Clauses 70
e)
and 71).
All the above-mentioned methods are practically equivalent. The application of one or another
method depends on the design and the apparent power of the machine under test.
23. Rated excitation current
Ifn
The current in the excitation winding when the machine operates at rated voltage, current,
power-factor and speed.
23.1 The rated excitation current is determined by the following methods:
a) direct measurement during operation under rated conditions;
graphically, by Potier's vector diagram (see Clause 31) or by the ASA diagram (see Clause 32) or
b)
by the Swedish diagram (see Clause 33).
The method of direct measurement is preferred, but the graphical methods are practically
equivalent to it.
24. Rated voltage regulation A Un
The change in the terminal voltage when rated operation is replaced by no-load operation with
the armature open-circuited and with unchanged speed and excitation current.
The rated voltage regulation is determined by the following methods:
a) direct measurement;
b) graphically, from the no-load characteristic (see Sub-clause 25.1) and the rated excitation current
(see Clause 23 and Sub-clause 23.1) obtained from tests.
SECTION FOUR — DESCRIPTION OF THE TESTS AND DETERMINATION
OF MACHINES QUANTITIES FROM THESE TESTS
25. No-load saturation test
The no-load saturation test is conducted:
by driving the tested machine as a generator by some prime-mover;
a)
b) by running the tested machine as a motor without shaft load from a source of alternating
symmetrical three-phase voltage;
c) during retardation of the tested machine.
During the no-load saturation test, excitation current, line voltage and frequency (or speed)
should be measured simultaneously. When making the no-load test, excitation changes should be
made in gradual steps from high to low voltage with points distributed evenly; if possible, from the
voltage value corresponding to the excitation at rated load, but not below 1.3 of the rated voltage of
the machine under test, down to 0.2 of its rated voltage, unless the residual voltage is higher.
When the excitation current is decreased to zero, the residual voltage of the generator is
measured.
If the no-load saturation test is conducted when the synchronous machine is running as an
unloaded motor, then in addition to the measured quantities mentioned above, it is necessary to

34-4 © IEC 1985 — 31 —
measure armature current. At each voltage step, readings should be taken for minimum armature
current which corresponds to unity power-factor.
The no-load saturation test during retardation of the tested machine may be performed with due
precision provided its rate of deceleration is not more than 0.04 of the rated speed per second.
If the machine under test has a rate of deceleration above 0.02 rated speed per second, excitation
from a separate source is required in order to have more stable excitation during the test. Before
disconnecting from the line, the machine is excited to the highest required value, but not below 1.3
of the rated voltage of the machine. The excitation is lowered in steps and at each step, readings of
armature voltage and speed (frequency) are taken simultaneously with constant excitation current.
The retardation test may be repeated to obtain all the steps required.
25.1 The no-load saturation characteristic—the relationship between the armature open-circuit winding
voltage at the terminals and the excitation current at rated speed (frequency)—is drawn from the
data of the no-load test. If, due to high residual voltage, the no-load characteristic cuts the axis
above the o
rigin, a correction should be introduced. To determine this, the straight po rtion of the
no-load curve, which is usually called the air-gap line, is projected to the point of intersection with
the abscissa axis. The length on the abscissa axis cut by this projected curve represents the correc-
tion value which should be added to all the measured values of the excitation current (Figure 1,
page 33).
If the frequency while conducting the test differs from the rated value, all the measured voltage
values should be referred to the rated frequency.
Sustained three-phase short
26. -circuit test
The sustained three-phase short-circuit test is conducted by:
a) driving the tested machine as a generator by some prime-mover;
b) during retardation of the tested machine.
The short circuit should be made as close to the machine terminals as possible, the excitation
current being applied after closing the short-circuit.
During the sustained three-phase short-circuit test, excitation current and armature line current
should be measured simultaneously. One of the readings is taken at a current close to the rated
armature current. The speed of rotation (or frequency) may differ from the rated value but should
not fall below 0.2 of rated value.
The sustained three-phase short-circuit test during retardation of the tested machine may be
performed with due precision, provided its rate of deceleration is not more than 0.10 rated speed
per second. If the machine under test has a rate of deceleration above 0.04 rated speed per second,
excitation from a separate source is required in order to have more stable excitation during the
test.
26.1 The three-phase sustained short-circuit characteristic, the relationship between the armature short-
circuited winding current and the excitation current, is drawn from the data of the three-phase
sustained short-circuit test.
27.
Determination of quantities from the no-load saturation and sustained three-phase short-circuit
characteristics
Direct-axis synchronous reactance (see Clause 4 and Sub-clause 4.1) is determined from the
no-load saturation and three-phase sustained short-circuit characteristics as a quotient of the

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34-4 © IEC 1985
no-load voltage taken from the air-gap line at some excitation and the sustained short-circuit
current value taken from the short-circuit characteristic at the same excitation current (Figure 1):
Un ^ _ACOH_ 1
X
^
d y , IBC d BC OC ifg
LX ^ J
determined in such a way corresponds to an unsaturated state of the
The value of Xd
machine.
FIGURE 1
27.1 Short-circuit ratio (see CIause 5 and Sub-clause 5.1) is determined from the no-load saturation and
three-phase sustained short-circuit characteristics as a quotient of the excitation current corres-
ponding to the rated voltage on the no-load saturation curve and the excitation current correspond-
ing to the rated current on the short-circuit curve (Figure 1):
_
_ OD
ifo
K^
OH
lfk
28. Overexcitation test at zero power-factor
The overexcitation test at zero power-factor is conducted with the machine operating as a
generator or as a motor. The active power when the machine operates as a generator should be equal
to zero. When the machine operates as a motor, the load on the shaft should be zero.
During the test, the excitation current is determined corresponding to values of voltage and
armature current preferably differing by not more than ± 0.15 per unit from the rated values, at zero
power-factor with overexcitation.

34-4 © IEC 1985 — 35 —
29. Determination of the excitation current corresponding to the rated voltage and rated armature current
at zero power-factor (overexcitation)
If, during the overexcitation test at zero power-factor, the voltage differs from the rated value by
not more than ± 0.15 per unit, a graphical method is used for the determination of the excitation
current corresponding to the rated voltage and current, using the data of the test and the no-load
saturation (see Sub-clause 25.1) and sustained three-phase sho rt
circuit (see Sub-clause 26.1)
characteristics.
An experimental point is plotted on a diagram with the no-load saturation curve of the test
machine. This point corresponds to zero power-factor and the measured values of the current
i,
voltage u and excitation current i
f (point C, Figure 2).
u
1.0
FIGURE 2
Vector OD equal to the excitation current, corresponding to the armature current i on the
three-phase short-circuit curve, is laid off along the abscissa axis. From the point C, a length CF
e
...