GB/T 22670-2008 (GB/T 22670-2018 Newer Version) PDF English
GB/T 22670-2008 (GB/T22670-2008, GBT 22670-2008, GBT22670-2008)
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Test procedures for converter-fed three phase cage induction motors
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Test procedures for converter-fed three phase cage induction motors
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Newer version: GB/T 22670-2018 Standards related to (historical): GB/T 22670-2018
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GB/T 22670-2008: PDF in English (GBT 22670-2008) GB/T 22670-2008
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 29.160.30
K 20
Test procedures for converter-fed three phase cage induction
motors
[Replaced]
ISSUED ON: DECEMBER 31, 2008
IMPLEMENTED ON: NOVEMBER 01, 2009
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative references ... 4
3 Terms and definitions, symbols ... 5
4 Test requirements ... 10
5 Test preparation ... 13
6 No-load test ... 16
7 Locked-rotor test ... 18
8 Load test ... 21
9 Determination of loss (applicable to voltage source converter) ... 23
10 Determination of efficiency ... 29
11 Base rating thermal test ... 34
12 Determination of maximum torque ... 45
13 Determination of minimum torque ... 49
14 Other tests ... 50
15 Calculation format ... 57
Appendix A (Normative) Correction method of instrument loss and error ... 67
Appendix B (Normative) Correction of dynamometer’s torque reading ... 72
Appendix C (Informative) Linear regression analysis ... 74
Test procedures for converter-fed three phase cage induction
motors
1 Scope
This standard specifies the test procedures for converter-fed three-phase cage induction
motors.
This standard applies to converter-fed three-phase cage induction motors.
This standard does not apply to traction motors.
2 Normative references
The terms in the following documents become the terms of this standard by reference
to this standard. For dated references, all subsequent amendments (not including errata
content) or revisions do not apply to this standard. However, parties to agreements that
are based on this standard are encouraged to study whether the latest versions of these
documents can be used. For undated references, the latest edition applies to this
Standard.
GB 755-2008, Rotating Electrical Machines - Rating and Performance (IEC 60034-
1:2004, IDT)
GB/T 755.2-2003, Methods for determining losses and efficiency of rotating
electrical machinery from tests (excluding machines for traction vehicles) (IEC
60034-2:1972, IDT)
GB/T 1032-2005, Test procedures for three-phase induction motors
GB 10068-2008, Mechanical vibration of certain machines with shaft heights 56 mm
and higher-measurement evaluation and limits of vibration severity (IEC 60034-
14:2003, IDT)
GB/T 10069.1-2006, Measurement of airborne noise emitted by rotating electrical
machines and the noise limits - Part 1: Method for the measurement of airborne noise
emitted by rotating electrical machines (ISO 1680:1999, MOD)
IEC 60034-2-1:2007, Rotating electrical machines - Part 2-1: Standard methods for
determining losses and efficiency from tests (excluding machines for traction
vehicles)
fr = 10f1 – for six-step wave converter
fr = 6fp – for PWM converter, the maximum is 100 kHz
Where:
f1 – the maximum rated frequency;
fp – the maximum pulse frequency (carrier frequency).
For six-step wave converters, ordinary electric instruments can meet these requirements;
for PWM converters, wide-band equipment must be used, and electronic instruments
with AD converters and digital data microprocessors are preferred.
Note 1: The two-meter method (Aron connection method) is not suitable for
applications with high pulse frequency. This is because the sum of the input
current phasors may not be zero due to the presence of capacitive current.
Therefore, the measurement method of using one power meter per phase shall
be adopted.
Note 2: The output harmonics of the converter and their main orders depend on the
modulation method.
Note 3: For commonly used indicating instruments, the accuracy is specified for the
nominal frequency (e.g., for 50 Hz ~ 60 Hz), and at the specified upper limit
frequency, the accuracy level allows additional errors (e.g., 0.4% for 1 000 Hz).
Electronic measuring instruments usually give a frequency range, which refers
to the specified upper limit frequency. The specified accuracy applies to both
50 Hz or 60 Hz, as well as the specified upper limit frequency.
4.3 Measurement requirements
4.3.1 Voltage measurement
The signal wire of the measuring terminal voltage shall be connected to the motor
terminal. If this connection is not allowed on site, the error caused by this shall be
calculated and the reading shall be corrected. Take the arithmetic average of the three-
phase voltage to calculate the motor performance.
The symmetry of the three-phase voltage shall meet the requirements of 4.2.1.2 in GB/T
1032-2005.
4.3.2 Current measurement
The line current of each phase of the motor shall be measured at the same time. Use the
arithmetic average of the three-phase line current to calculate the performance of the
motor.
When using a current transformer, the total impedance of the secondary loop instrument
(including the connecting wire) as connected shall not exceed its rated impedance.
For motors with IN < 5 A, current transformers shall not be used except for the locked-
rotor test (see GB/T 1032-2005).
4.3.3 Power measurement
One three-phase power meter or three single-phase power meters shall be used to
measure the input power. For occasions where the pulse frequency is not high, it may
ignore the influence of the capacitance current. It may also use the two-meter (two
single-phase power meters) method to measure the input power of the three-phase motor.
If the instrument loss affects the accuracy of the test results, the instrument loss and its
error may be corrected according to Appendix A (see GB/T 1032-2005).
4.3.4 Torque measurement
The load test shall be carried out with a torque measuring instrument of appropriate
specifications.
In addition to the locked-rotor test, the measurement of the maximum torque and the
minimum torque, the nominal torque of the torque measuring instrument shall not
exceed 2 times the rated torque of the motor under test. When the motor under test is at
the rated speed, the measured wind friction loss of the coupling and dynamometer (or
load motor) shall not be greater than 15% of the rated output of the motor under test,
and the sensitivity of torque changes shall reach 0.25% of the rated torque. The
mechanical power shall be measured accurately and the correction value kd of the torque
reading Td shall be determined according to the method given in Appendix B (see GB/T
1032-2005).
4.3.5 Measurement of speed and slip
Measure the speed with a digital tachometer. If the induction coil method or flash
tachometer is used to directly measure the slip, the power supply shall be the power
supply of the motor under test (see GB/T 1032-2005).
4.3.5.1 Flash method
On the end face of the motor shaft, draw the same number of segments as the number
of poles of the motor and illuminate them with fluorescent or neon lamps. The power
frequency supplied to the flash fixture must be the same as the power frequency of the
motor under test. During the test, use a stopwatch to measure the time t (s) required for
the segment to rotate N times. Calculate the slip St according to formula (1):
process is to first take the reading at the maximum load; then take the reading at the
lower load.
8.1.2 Base rating load test
The test shall be carried out at rated voltage and fundamental frequency. Before starting
to read test data, the difference between the stator winding temperature and the
temperature measured during the rated load thermal test shall not exceed 5K.
Use appropriate equipment (e.g., dynamometer, test motor) to load the motor. Use a
torque measuring instrument that meets the requirements of 4.3.4 to measure the torque
(only when using method A or method B).
Load the motor at 6 load points. The four load points are roughly evenly distributed
between no less than 25% ~ 100% of the rated load (including 100% of the rated load),
and two load points are appropriately selected between greater than 100% but no more
than 150% of the rated load. The process of adding load to the motor is to start from the
maximum load and gradually reduce it to the minimum load in sequence. The test shall
be carried out as quickly as possible in order to reduce the temperature change of the
motor during the test.
At each load point, measure U, I1, P1, Td, n (or st), f, θt (or Rt) and θf.
It is recommended to use a temperature sensor (embedded at the end of the stator coil)
to measure the temperature of the winding.
When measuring the fundamental loss of the motor according to method B, θt or Rt at
each point must be measured; when determining the fundamental loss of the motor
according to method E1, the method specified in a) below is allowed to be used to
determine the resistance value at each load point; when determining the fundamental
loss of the motor according to other methods specified in this standard, the method
specified in b) below is allowed to be used to determine the resistance value at each
load point.
a) The resistance value at each load point at 100% rated load and above is the
resistance value before the maximum load point reading. The resistance value at
each point less than 100% rated load is determined in a linear relationship with
the load. The starting point is the resistance value at 100% rated load, and the end
point is the resistance value after the minimum load reading.
b) After the load test, immediately measure the stator winding end resistance and use
this resistance as the resistance value of each load point.
8.2 Determination of load characteristics of converter-fed motors
After the motor’s thermal test, restart the motor and test the load characteristics. For
example, the motor which has a reference frequency of 50 Hz, respectively adjust the
In motors powered by converters, voltage harmonics and current harmonics cause
additional iron losses and winding I2R losses in the motor stator and rotor. This
additional loss is collectively called harmonic loss.
As far as motors powered by voltage source converters are concerned, many tests have
proven that the size of harmonic losses has nothing to do with load changes (see IEC
TS 60034-17:2006, Chapter 5).
The loss of the motor consists of two parts: fundamental loss and harmonic loss.
10.2.2.1 Harmonic losses
The harmonic loss Pbh is determined according to 6.2.2.
10.2.2.2 Fundamental losses
The motor under test is powered by a sine wave power supply, and the fundamental loss
is determined according to the following methods specified in GB/T 1032-2005:
a) Method B (see 10.4);
b) Method E1 (see 10.5);
c) Method F1 (see 10.6);
d) Method G1 (see 10.7);
e) Method H (see 10.8).
10.2.2.3 Determination of efficiency
The corrected sum of fundamental losses PT is determined according to formula (34),
the corrected total loss ΣP of the motor is determined according to formula (35), and
the efficiency of the motor is determined according to formula (38).
10.3 Method A – input-output method (applicable to voltage and current source
converters)
This method uses the ratio of measured output power to input power to calculate
efficiency. Usually used for motors with an efficiency not greater than 90% (see 7.1 in
GB/T 755.2-2003).
10.3.1 Test procedure
During the test, the motor under test is powered by the converter power supply and
reaches a thermally stable state under rated load. Carry out load test according to the
method specified in 8.1.2.
10.3.2 Calculation format
R1 – the initial end resistance of the winding when the temperature is θ1, in ohms (Ω);
θa – the cooling medium temperature at the end of the thermal test, in degrees Celsius
(°C);
θ1 – the winding temperature when measuring the initial end resistance R1, in degrees
Celsius (°C);
K1 – constant. For copper windings, it is 235; for aluminum windings, it is 225, unless
otherwise specified.
Since the deviation of the measured resistance will cause a large error when determining
the temperature, the instrument required in 4.3.6 of GB/T 1032-2005 shall be used to
measure the winding resistance. If possible, a second instrument can be used for
inspection. The initial resistance and the resistance at the end of the test shall be
measured using the same instrument.
11.1.3.3 Embedded thermometer method
This method uses a thermocouple installed in the motor or a resistance thermometer to
measure the temperature.
Specially designed instruments shall be used with resistance thermometers to prevent
the heating of the resistance thermometer from introducing significant errors or
damaging the instrument during measurements. Many ordinary resistance-type
measuring devices may not be suitable because considerable current may flow through
the resistor element during the measurement.
11.1.4 Temperature reading
11.1.4.1 General description
The following subclauses introduce 3 temperature measurement methods for
determining the temperature of the motor’s windings, stator core, entered cooling
medium, and discharged cooling medium after being heated. Each measurement
method has its own characteristics and is suitable for measuring the temperature of
specific parts of the motor.
11.1.4.2 Thermometer method
During the thermal test, the temperature of the following components can be measured
using the thermometer method (see 11.1.3.1). If specified, measurements can be made
after shutdown.
a) stator coil, at least in 2 locations;
b) stator core, for large and medium-sized motors, at least in 2 locations;
c) ambient temperature;
d) the air discharged from the machine base or exhaust ventilation duct or the internal
cooling medium discharged from the motor with a circulating cooling system to
the cooler inlet;
e) machine base;
f) bearings (if they are motor components).
The temperature sensitive element shall be placed where the highest temperature can
be measured. For the temperature of air or other cooling media in the incoming and
outgoing airflow, the sensitive element shall be placed where the average temperature
can be measured.
11.1.4.3 Embedded thermometer method
During the motor thermal test with an embedded thermometer in the winding, the
winding temperature shall be measured using the embedded thermometer method (see
11.1.3.3) and written in a report. Generally, it is not required to take readings after
shutdown.
11.1.4.4 Resistance method
The temperature of the stator winding can be measured using the resistance method (see
11.1.3.2) after shutdown. The resistance between any two wire terminals shall be
measured directly at the motor outlet terminal, and the initial value and initial
temperature of this resistance have been measured.
11.1.5 Determination of cooling medium temperature during thermal test
11.1.5.1 Air-cooled motor
For motors cooled by ambient air, several thermometers can be used to measure the
cooling air entering the motor. The thermometer shall be placed about 1 m ~ 2 m away
from the motor, with the ball at half the height of the motor, and shall be protected from
the influence of external radiant heat and airflow. Take the arithmetic mean of the
thermometer readings as the cooling medium temperature.
11.1.5.2 External cooler motor
For motors using external coolers and ducted ventilation cooling, the temperature of the
cooling medium shall be measured at the entrance of the cooling medium into the motor.
11.1.5.3 Inner cooler motor
For motors which are cooled by internal coolers, the temperature of the cooling medium
shall be measured at the outlet of the cooler. For motors which are cooled by water-
cooled coolers, the water temperature shall be measured at the inlet of the cooler.
11.1.5.4 Determination of the cooling medium temperature at the end of test
11.1.5.4.1 Constant rating and intermittent duty motors
For motors with a constant rating and intermittent duty system, the cooling medium
temperature at the end of the test shall be the average of the thermometer readings as
measured at the same time interval during the last 1/4 of the entire test process.
11.1.5.4.2 Short-term rated motors
For a short-time rated motor, the cooling medium’s temperature at the end of the test is,
if the rating is 30 min or below, the average of the thermometer’s readings at the
beginning and the end of the test. If the rating is 30 min ~ 90 min, take the reading of
the thermometer at the 1/2 of the test time and the reading of the thermometer at the
end.
11.1.6 Temperature measurement of motor windings and other parts
11.1.6.1 Measurement of winding temperature
The temperature of the motor windings is measured by the resistance method. Priority
shall be given to the dual-bridge live temperature measurement method. If the motor
has an embedded thermometer, use the thermometer to measure it.
11.1.6.2 Measurement of core temperature
The core temperature is measured using a thermoscope or thermometer. For large and
medium-sized motors, there shall be no less than 2 thermometers, and the highest value
is taken as the core temperature.
11.1.6.3 Measurement of bearing temperature
The bearing temperature is measured by a thermometer. For sliding bearings, the
thermometer is placed in the temperature measurement hole of the bearing or placed
close to the surface of the bearing bush. For rolling bearings, the thermometer is placed
closest to the outer ring of the bearing.
11.2 Thermal test method
The thermal test method has direct load method and equivalent load method. It shall
give priority to the direct load method.
The equivalent load method includes reduced voltage load method, reduced current load
method, and stator overlap frequency method. The equivalent load method is limited to
I1 – the primary current of induction motor;
U2 – auxiliary voltage;
f2 – auxiliary power frequency;
P1 – input power.
Note 1: The auxiliary power supply’s phase sequence shall be the same as the main
power supply.
Note 2: U2 shall be smaller than U1 (usually 10% ~ 20% of U1). U2 is the voltage value
to be applied to produce the rated current I1.
Figure 6 – Test circuit diagram of stator overlap frequency method
When using the stator overlap frequency method, the phase sequence of the main and
auxiliary power supplies applied to the tested motor windings shall be the same. The
motor under test can be started separately by the main and auxiliary power sources
before wiring. If the directions of rotation are the same, it is the same phase sequence.
During the test, first use the main power supply to start the motor under test, to make it
run at no-load at rated frequency and rated voltage. Subsequently, start the auxiliary
power unit and adjust its speed to a speed value corresponding to a certain frequency f2.
For a motor with a rated frequency of 50 Hz, f2 shall be selected within the range of 38
Hz ~ 42 Hz. Then, put the auxiliary power generator into excitation and adjust the
excitation current, so that the stator current of the motor under test reaches the full load
current value. During the loading process, the main power supply voltage shall be
adjusted at any time, to keep the terminal voltage of the motor under test at the rated
value; meanwhile keep the frequency f2 unchanged. The full load current value of the
tested motor at rated voltage can be determined according to the method of 10.6 or 10.8.
The test requirements are the same as 11.2.1.1.
When adjusting the load of the motor under test, if the instrument pointer swings large
or the vibration of the motor under test and the test power supply equipment is large,
the auxiliary power supply voltage shall be reduced first; then another value of
frequency f2 shall be selected by adjusting the speed of the auxiliary power supply unit
for the test again.
11.2.3 Initial state
The test shall be carried out continuously within the specified time (for motors of non-
constant rating) or until the temperature stabilizes. Unless otherwise specified, the
short-term rated thermal test can only be started when the temperature difference
between each part of the motor and the environment is within 5 K.
11.2.4 Allowed overload
same as those during calibration. During the test, the excitation current shall remain
unchanged.
During the test, connect the motor under test with the dynamometer or the calibrated
DC motor by a coupling, so that the rotation direction of the two is consistent. Gradually
increase the load of the motor under test until the dynamometer’s reading or the
armature current of the corrected DC motor has the maximum value; read this value
and the terminal voltage of the motor under test. When using a calibrated DC motor,
read the speed value at the same time.
During the test, the motor under test shall be prevented from overheating and affecting
the accuracy of the measurement. The terminal voltage of the motor under test shall be
measured on its outlet terminal.
12.3 Torque measuring instrument method
When using the torque measuring instrument method to determine the maximum torque,
it shall measure the torque-speed characteristic curve of the motor under test. The
maximum torque is obtained from the curve.
The torque-speed characteristic curve can be drawn manually after point-by-point
determination; or can be drawn directly by an automatic recorder. For fractional
horsepower and small motors, both methods can be used. The former shall be used for
medium-sized motors which use rolling bearings. When determining the torque-speed
characteristic curve point by point, the number of points measured shall meet the needs
of correctly obtaining various torques (maximum torque, minimum torque,
synchronous torque, locked-rotor torque). Near these torques, the measuring points
shall be as dense as possible.
During the test, the motor under test shall be prevented from overheating and affecting
the accuracy of the measurement. When necessary, the torque-speed characteristic
curve can be measured in sections.
When a DC motor is used as the load, the motor under test is connected to the sensor
and DC motor by a coupling. The DC motor is separately excited; its armature is
powered by an adjustable voltage and variable polarity power supply. The rotation of
the tested motor and the DC motor shall be consistent. Adjust the power supply voltage
of the DC motor; gradually increase the load of the motor under test; read the torque,
speed and voltage values at the same time. Or use an automatic recorder to describe the
torque-speed characteristic curve, the relationship curve between the voltage at the
motor terminal and the speed under test. When using an automatic recorder to plot the
curve, it is recommended to measure two torque-speed characteristic curves when the
motor speed under test is rising and falling; take the average value. The drawing time
of each curve shall not be less than 15 s.
12.4 Torque tachometer method
......
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.
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