GB/T 1032-2023Test methods for three-phase asynchronous motors (English PDF)

1 Scope

China's national test code for three-phase asynchronous motors - the induction motor being the workhorse that consumes a very large share of all industrial electricity, and this being the document that decides what its efficiency is. It describes the test requirements and the test methods for three-phase asynchronous motors, including the measurement of insulation resistance, the measurement of DC resistance, the thermal test, the load test, the no-load test, the locked-rotor test, the determination of the losses and the efficiency, the torque-speed characteristic test, the moment of inertia test, the short-time over-torque test and the further tests a motor may be subjected to. It applies to the testing of three-phase asynchronous motors. The determination of efficiency is the part with consequences. A motor's efficiency can be found by measuring input and output directly, or by measuring the individual losses and subtracting them - and the two do not necessarily agree, because the stray load loss is difficult to measure and has historically been assigned a conventional value rather than determined. Which method a standard prescribes therefore decides what a motor's efficiency is said to be, and by extension whether it meets the mandatory energy efficiency grades set elsewhere. That is why a test code of this kind carries as much commercial weight as the efficiency standard it serves. The rest of the document covers the tests that establish whether the machine is fit at all: the insulation resistance and the withstand voltage, the thermal test that determines the temperature rise and therefore the rating, the locked-rotor and starting characteristics, the torque-speed curve, the vibration and noise, and the over-torque capability. Issued on 7 September 2023 and in force since 1 April 2024, it replaces GB/T 1032-2012. Amendment 1, GB/T 1032-2023/XG1-2025, was issued on 30 June 2025 and forms part of the same document.

This Document describes the test requirements and test methods for three-phase asynchronous motors. Test methods include measurement of insulation resistance, measurement of DC resistance, thermal test, load test, no-load test, locked-rotor test, determination of loss and efficiency, torque speed characteristic test, moment of inertia test, short-time over-torque test, Inter-turn insulation impulse voltage test, power frequency withstand voltage test, rotor open circuit voltage measurement, overspeed test, vibration and noise measurement, shaft voltage and bearing current measurement. This Document applies to three-phase asynchronous motors.

2 Normative References

The provisions in following documents become the essential provisions of this Document through reference in this Document. For the dated documents, only the versions with the dates indicated are applicable to this Document; for the undated documents, only the latest version (including all the amendments) is applicable to this Document.

GB/T 755-2019 Rotating electrical machines - Rating and performance

GB/T 10068-2020 Mechanical vibration of certain machines with shaft heights 56 mm and higher - Measurement, evaluation and limits of vibration severity

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

GB/T 21211-2017 Rotating electrical machines - Equivalent loading and super-position techniques - Indirect testing to determine temperature rise

GB/T 22715-2016 Impulse voltage withstand levels of form-wound stator coils for rotating A.C. machines

3 Terms and Definitions

For the purposes of this Document, the terms and definitions given in GB/T 755-2019 and GB/T 25442-2018, and the following apply.

3.1 Asynchronous machine An A.C. motor, the ratio of its speed under load to the frequency of the connected power grid is not a constant value. [Source: GB/T 2900.25-2008, 411-31-09]

3.2 Motor A motor that converts electrical energy into mechanical energy. [Source: GB/T 2900.25-2008, 411-33-01]

3.3 Type test A test that is carried out on one or more motors manufactured according to a certain design to show that the design complies with certain standards. [Source: GB/T 2900.25-2008, 411-53-01]

3.4 Routine test A test that is conducted on each motor after it is manufactured to determine whether it meets the standards. [Source: GB/T 2900.25-2008, 411-53-02]

3.5 Insulation resistance test A test that measures insulation resistance under specified conditions. [Source: GB/T 2900.25-2008, 411-53-48]

3.6 Thermal test A test that determines the temperature rise of one or several parts of the motor under specified operating conditions.

3.7 Load test A test that determines the load characteristics of the motor under specified operating conditions.

3.8 No-load test A test without effective mechanical output on the shaft when the motor is running.

3.9 Locked-rotor test A test that is carried out to determine the locked-rotor torque and locked-rotor current when the motor is energized and the rotor is blocked. [Source: GB/T 2900.25-2008, 411-53-32]

3.10 Efficiency The ratio of output power to input power, which is usually expressed as a percentage. [Source: GB/T 2900.25-2008, 411-53-08]

3.11 Impulse test A test in which a non-periodic transient voltage is applied to an insulating component. The polarity, amplitude and waveform of the test voltage must comply with predetermined provisions. [Source: GB/T 2900.25-2008, 411-53-55]

4 Denotations

cosphi. Power factor. f. Power supply frequency (Hz). I

5 Test Requirements

5.1 General description The performance of three-phase asynchronous motor is closely related to the supply voltage and frequency; while it is affected by the voltage wave shape, the symmetry of supply power, the frequency deviation and stability. Accurate test data can only be obtained with qualified power supply (see 5.2), test apparatus (see 5.3) and careful measurement.

7 Thermal Test

7.1 Objective The objective of thermal test is to determine the temperature rise when parts of the motor operating under the specified load conditions have a temperature higher than that of the cooling agent.

7.2 General description Protective measures shall be taken for the motor to be tested against the impact of airflow caused by other mechanical parts on the tested motor. In practice, great deviation of the thermal test result may be caused by even very small airflow. Ambient condition that may cause rapid change to the ambient air temperature is not advisable for temperature rise test. Adequate space shall be available between motors so that good ventilation can be obtained. In order to avoid errors caused by the time lag led by the inability of the temperature of large motors to change quickly with the corresponding changes in the temperature of the cooling medium, all appropriate measures shall be taken to reduce the changes in the temperature of the cooling medium. At the beginning of the thermal test, all temperature measuring devices shall be checked to ensure that they do not increase the temperature measurement error due to the influence of stray magnetic fields. The temperature of the fully enclosed motor rotor and other parts can be quickly measured with a temperature measuring device after the power is shut down.

8 Load Test

8.1 General The objective of load test is to determine the motor efficiency, power factor, rotating speed, stator current, and the relationship between input power and output power. The test adopts the direct load method, using suitable equipment (such as D.C. motor or three-phase induction motor, etc.) to add load to the motor. The axis of the load equipment shall have a high degree of co-axiality with the axis of the motor under test, so that ensure safe operation.

8.2 Test procedure The test shall be done under the rated voltage and frequency. The test should be carried out immediately after the rated load thermal test. If this is not possible, the difference between the stator winding temperature and the temperature measured in the rated load thermal test shall not exceed 5K before starting to read and record the test data. Apply load to the motor on at least 6 load points. approximately 125%, 115%, 100%, 75%, 50% and 25% of the rated load. The process of applying load is to start from the maximum load and reduce to the minimum load in sequence. The test shall be completed as soon as possible to reduce the impact of motor temperature changes on the test results during the test. The frequency variation of the power supply shall not exceed ±0.1% at all load points. At each loading point, measure U, I1, P1, Td (if any), n (or st), f, thetat or Rt (if any), and thetaa. It should use a temperature sensor (embedded at the end of stator winding) to measure the winding temperature. When the motor efficiency is measured with Methods B or A, thetat and Rt at each point shall be measured in the following

a) of this subclause. When the motor efficiency is measured with Methods C, E or E1, it is allowable to determine the resistance at each loading point in accordance with the procedures described in the following b). If the motor efficiency is determined with other methods specified in this Document, it is allowable to determine the resistance at each point in accordance with the procedures described in the following c). There are 3 methods to measure the resistance at each load point.

a) Preset a temperature sensor on the stator winding, and determine its resistance value by measuring the temperature thetat of the stator winding. That is, according to the proportional relationship between temperature and resistance, the resistance value of each load point can be determined by using the initial resistance and initial temperature of the winding measured before the start of the test and the temperature of each point measured.

b) The resistance value greater than and equal to 100% of the rated load point 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.

c) After the load test is completed and the power is turned off, the stator winding resistance is immediately measured and used as the resistance value of each load point.

9 No-Load Test

9.1 General During the no-load test, there is no effective mechanical power output at the shaft end of the motor under test. The rotor winding of a wound rotor motor shall be short-circuited on the slip ring.

9.2 Test procedure The test shall be carried out in the hot state immediately after the completion of the thermal test and load test. If this is not feasible, the test data can also be read and recorded after the input power of the motor is stable, that is, the difference between two consecutive input power readings at interval of 30 min should be no greater than 3% of the previous reading. For water-air cooling motors, the water source shall be cut off immediately after the thermal test (or load test). During the inspection test, the no-load running time can be shortened appropriately, and P0, U0 and I0 can be measured at only one test point with the rated voltage value. The motor under test is applied with a variable voltage of rated frequency, and the following 8 voltage points are tested.

--- Take 4 test points at approximately 110%, 100%, 95% and 90% of the rated voltage to determine the iron loss;

--- Take 4 test points of about 60%, 50%, 40% and 30% of the rated voltage to determine the air friction loss. The tests shall be carried out as rapidly as possible in a sequence of gradually decreasing voltages. At each voltage point, measure P0, U0 and I0, and measure the winding temperature theta0 or end resistance R0 (if any) at the same time. When method A or method B is used to determine the efficiency, the R0 of each voltage point shall be determined, as in

a) of this article; when other methods are used to determine the efficiency, the winding resistance value R0 of each voltage point shall be determined according to one of the following methods. There are several methods to determine the resistance value R0 of each voltage point as follows:

a) Preset a temperature sensor in the stator winding, and determine its resistance value by measuring the temperature theta0 of the stator winding. That is, according to the proportional relationship between temperature and resistance, the resistance value of each voltage point can be determined by using the initial resistance and initial temperature of the winding measured before the start of the test and the measured temperature at each point. If theta0 is measured, the end resistance R0, in Omega, is calculated according to Formula (29). Where. R1 - Stator winding initial (cold state) end resistance, in Omega; theta1 - Stator winding temperature when measuring R1, in °C.

b) Immediately measure the stator winding resistance R0 before and after the no-load test. The stator winding resistance value of each intermediate test point shall be calculated and determined by interpolation method according to the linear relationship with the electric power P

0.The starting point is the resistance value measured before and after the test.

c) After the no-load test is completed and the power is turned off, the stator winding resistance is immediately measured and used as the resistance value of each voltage point.