[Guide] After the specified load is applied to the tested motor and it runs to a stable temperature rise or a specified time (when using the latter method, the difference between the temperature reached by the winding of the tested motor and the actual temperature rise stable should be No more than 5K), adjust the load to change within the range of 1.5 to 0.25 times the rated power, and measure the two working characteristic curves when the load falls and rises.

Efficiency is a very important performance index of the motor. Especially under the guidance of energy conservation and emission reduction policies, motor users pay special attention to the efficiency index of the motor. If you want to accurately determine the efficiency of the motor, you need to type test, and through a suitable, standardized efficiency test method. Taking the three-phase asynchronous motor efficiency determination method as an example, it can be roughly divided into three categories. The first category is the direct measurement method; the second category is the indirect measurement method, also known as the loss analysis method; the third category is a method that uses theoretical calculation after a simple test, which is simply called the theoretical calculation method.

The direct measurement method is intuitive, simple, and has high relative accuracy, but it is not conducive to the specific analysis of the performance of the motor and targeted improvement; the indirect measurement method has more test items, is time-consuming and labor-intensive, and has more calculations and comprehensive accuracy. It is not as good as the direct measurement method, but it can show the specific conditions of the main components that determine the efficiency of the motor, so as to facilitate the targeted analysis of the problems in the design, process and manufacturing of the motor, and improve the motor performance to meet the requirements Further improvement; the theoretical calculation method is used when the test equipment is insufficient, and the accuracy is the worst.

Direct test method for efficiency

It is also often called the input-output method. It is named because it can directly obtain the two data for efficiency, namely the input power and the output power.

After the motor under test is added with a specified load and the temperature rise is stable or a specified time (the latter method is used, the difference between the temperature reached by the motor winding under test and the temperature reached by the actual temperature rise should not exceed 5K ), Adjust the load to change within the range of 1.5 ~ 0.25 times the rated power, and measure the two working characteristic curves when the load falls and rises. Each curve takes no less than 6 points of reading. Each point of reading includes: three-phase line voltage (should maintain the rated value), three-phase line current, input power, speed, output torque, and output power should be recorded when conditions permit . Finally, when the power is turned off, the DC resistance of the stator winding is measured within the specified time. Otherwise, the extrapolation shall be carried out according to the relevant provisions for obtaining the thermal resistance after the thermal test.

When conditions permit, it is preferred to use live measurement (superposition method) or a temperature sensor such as a thermocouple or copper (platinum) thermal resistance embedded in the winding in advance to obtain the temperature or resistance of each stator winding. During the test, the ambient temperature should also be recorded.