GB/T 5171.21-2016Small power motors—Part 21: General test methods (English PDF)

3.1 Terms and definitions

For the purposes of this document, the terms and definitions defined in GB/T 5171.1 and GB 12350 as well as the followings apply.

3.1.1 Efficiency

the ratio of output power to input power in the same unit, usually expressed as a percentage

3.1.2 Dynamometer

a device for measuring the torque applied to the rotating parts of the machine under test; the device can measure and display torque and speed, and is not limited to the bearing housing structure; the coaxial torque sensor can be used to directly measure the torque of the measured motor drive shaft

3.1.3 Thermal equilibrium

a state that the temperature rise of the heating parts of the motor does not exceed 1K within half an hour

3.1.4 Temperature-rise test

a test to determine the temperature rise of one or several parts of the motor, under specified operating conditions

3.1.9 Operating time limit test

a test to determine the normal operation period that the manufacturer guarantees to the user under the specified conditions

3.2 Symbols

The following symbols apply to this document. cos phi - Power factor;

4.1 Test ambient conditions

Ambient temperature. 15°C~30°C Relative humidity. 45%~75% Atmospheric pressure. 86kPa~106kPa The ambient temperature during temperature rise and efficiency test. 20°C ± 5°C. For motors equipped with thermostats or thermal fuse, if in doubt, the ambient temperature during the temperature rise test is maintained at 23°C ± 2°C.

4.2 Test power

4.2.1 AC power

The harmonic voltage factor (HVF) of the AC power supply used for the test shall not exceed 0.02. When conducting temperature rise and efficiency tests, the harmonic voltage factor (HVF) shall not exceed 0.015.

4.2.2 Three-phase AC power supply

For three-phase AC power supply, in addition to meeting the requirements in 4.2.1, the negative sequence component of the three-phase voltage system shall be less than 0.5% of the positive sequence component, and the influence of zero sequence component shall be eliminated. The negative sequence component of the measuring current system can be used to replace the negative sequence component of the measuring voltage system.

4.2.3 DC power supply

The DC power supply equipment used in the test shall not exceed 0.5% of the nominal source voltage and the output voltage tolerance of each output under half-rated load. For each output, within the specified load range and under the most unfavorable supply voltage, the load regulation rate is not more than 0.2%.

4.3.1 General

The ambient conditions during the test shall be within the range recommended by the equipment manufacturer. If applicable, temperature corrections shall be made to the measured values according to the manufacturer's equipment instructions.

4.3.2 Measurement of electric quantity

Unless otherwise specified, the accuracy of the electrical measuring instrument used shall not be less than level 0.5.

4.3.3 Torque measurement

The accuracy of the instrument used to measure torque shall not be less than level 0.5. When measuring efficiency, it shall not be less than level 0.2. The measured minimum torque shall be at least 10% of the rated torque of the torque measuring instrument. If a better grade measuring instrument is used, the allowable torque range is expanded accordingly.

4.3.4 Measurement of rotating speed

4.3.5 Frequency measurement

The accuracy level of the frequency meter shall not be less than level 0.1.

4.3.6 Temperature measurement

4.3.7 Determination of winding resistance

4.3.8 Other measuring instruments

In order to ensure the accuracy of the test results, other measuring instruments used in the test process shall also have sufficient accuracy, for example.

5.1 Determination of insulation resistance

5.1.1 State of motor during measurement

When measuring the insulation resistance of motor windings, it shall be respectively carried out under the actual cold state and thermally stable state (after the temperature rise test). During the exit-factory test, if there are no other provisions, the measurement is allowed in the actual cold state. When measuring the insulation resistance, the winding temperature shall be measured and recorded at the same time. When measuring in the actual cold state, the surrounding medium temperature can be used as the winding temperature.

5.1.2 Selection of megohmmeter

According to the rated voltage of the motor, select the megohmmeter according to Table 1.

5.1.3 Measurement methods

When measuring the winding insulation resistance, if the beginning and end of each winding circuit have been led out of the casing, then the insulation group of each winding circuit to the casing and the windings shall be measured separately. If the winding has been connected inside the motor, when only the wire end is drawn out, measure the insulation resistance of the wire end to the casing.

5.2 Determination of cold-state winding temperature theta

1 and cold-state winding resistance R1 Put the motor indoors for a period of time.

6.1 Overview

The purpose of the temperature rise test is to determine the temperature rise of windings and certain parts of the motor that are higher than the temperature of the cooling medium when the motor is running under specified load conditions.

The temperature measurement method is selected according to 4.3 and the relevant provisions of this Clause.

6.2 General description

Measures shall be taken during the test to minimize the change in the temperature of the cooling medium.

6.4 Temperature measurement methods for motor winding and other parts

6.4.1 Determination of winding temperature

The temperature of motor windings is measured by resistance method, including live temperature measurement method.

6.4.2 Determination of iron core temperature

The iron core temperature is measured with a thermometer or thermocouple.

6.5 Temperature rise test method

6.5.1 Determination of load

6.5.2 Duration of various motor temperature rise tests

6.5.4 Determination of winding resistance R2 measured by live temperature measurement method When using the live temperature measurement method, the measured additional current shall not exceed 1% of the rated current of the tested motor.

The stable response time of the thermometer does not exceed 40s.

6.6 Calculation of winding working temperature theta 2

The working temperature of the winding refers to the temperature of the winding when the motor reaches a thermally stable state during the rated load temperature rise test, calculated according to formula (9).

6.7 Calculation of winding temperature rise deltatheta

Winding temperature rise is calculated according to formula (11).

7.1 Overview

For motors with sealing rings, if there is no special agreement, the efficiency measurement shall be carried out after the sealing rings are removed.

7.2 Direct method (method A)

7.2.1 Overview

This is a test method in which the mechanical output power of a motor is determined by measuring the torque and speed of the shaft. The electrical input power of the stator is measured in the same test.

7.2.2 Determination of output power

7.2.2.1 Dynamometer method and torque measuring instrument method

Connect the tested motor and the dynamometer or load motor with a torque measuring instrument.

7.2.3 Calculation of efficiency

The efficiency eta of the motor at different loads is calculated according to formula (17). For dynamometer method and torque measuring instrument method, draw efficiency curve eta=f(P2).

7.3 Loss analysis method (method B)

7.3.1 Overview

This is a test method to determine efficiency by summing up various losses.

7.3.2 Test procedures

7.3.2.1 Rated load test

Winding temperature and resistance at ambient temperature

7.3.2.1 Rated load test

Winding resistance during rated load test

7.3.2.2 Load loss

Stator and rotor winding losses

7.3.2.3 Load curve test

Torque measurement and winding resistance measurement

7.3.2.4 No-load test

Winding resistance during no-load test

7.3.2.5 Constant loss

Wind resistance and friction loss, iron loss

7.3.2.6 Additional load loss

From stray loss

9.1 Dimension inspection

9.1.1 Shape and installation dimension inspection

Vernier caliper or micrometer can be used to check the appearance and installation dimensions of the motor.

9.1.2 Axial movement

The motor axis is placed horizontally and fixed on the plate. The measuring head of the dial indicator is placed on the top of the shaft extension. Apply the force specified in Table 3 to the shaft along the axis. First in one direction, then in the opposite direction.

9.1.3 Shape error and position error inspection

9.1.3.1 General

The testing principle, testing conditions, evaluation method and testing plan of the shape error and position error of the motor (hereinafter referred to as the shape and position error) shall meet the requirements of GB/T 1958.

9.1.3.2 Radial runout of shaft extension

The motor axis is placed horizontally and fixed on the plate. The measuring head of the dial indicator is placed at half of the shaft extension. Rotate the shaft slowly and steadily for one revolution.

9.1.3.5 Flatness of foot support surface

Place the motor on the plate. Use feeler gauge to measure the gap between the motor foot and the plate. Measure the straightness error values of several sections at different points. The maximum value is the flatness of the foot support surface.

9.1.3.6 Parallelism of motor axis to foot supporting surface

The motor axis is placed horizontally and fixed on the plate. The axis is simulated by the upper element line of the shaft extension. The values measured at two positions on the shaft extension with a measuring distance of L2 are M1 and M2, respectively. […]