A brief discussion on synchronous measurement of motor and driver

As we all know, a motor is a device that can convert electrical energy into mechanical energy. It is widely used in the fields of industry, agriculture, military industry, rail transportation, household appliances, medical treatment, etc. It can be said that it is everywhere. Especially with the development of variable frequency speed regulation technology in the industry, more and more motors support real-time control, because they have some irreplaceable characteristics: they can adjust the output speed and torque in real time according to the load requirements to achieve motion control or energy saving. These motors have one thing in common - they need driver control, and the most typical ones are servo motors and variable frequency motors.

For example, the traditional fan and water pump industry originally used three-phase asynchronous motors, but now they should use a combination of frequency converter + variable frequency motor to achieve speed control of the motor and achieve energy saving and emission reduction. For example, when the drainage load is high, the output power of the water pump motor is increased to achieve full load output; at night when the drainage load is small, the speed of the water pump motor is reduced through the frequency converter to reduce the output power of the water pump, thereby achieving energy saving.

Although variable frequency motors and brushless motors achieve better energy saving through motor control, they also introduce a new device - motor driver (inverter). Since motor drivers also have efficiency losses, we cannot only focus on the motor when evaluating motor performance, but must evaluate the driver and motor as a comprehensive system.

Importance of synchronous testing of motors and drives

In traditional motor testing, the efficiency of the motor is not constant, but varies with the speed (load). The same is true for motor drivers in terms of efficiency testing.

Therefore, in order to ensure the accuracy of the motor efficiency and motor driver efficiency test, it is necessary to ensure that the efficiency of both is measured under the same load, that is, to ensure that the data is collected at the same time point. A multi-channel power analyzer is generally used for measurement. As shown in the figure below, it is a very common method for synchronous testing of variable frequency motors and inverters.

In this system, the three-phase input and three-phase output of the inverter (motor driver) and the speed and torque output of the motor are all connected to the same device (power analyzer) for collection, and the efficiency calculation tool inside the device is used to achieve synchronous measurement of the efficiency of the motor, motor driver and the entire system. If the synchronization of the power analyzer is ensured to be good enough, such as the PA power analyzer used in the example, the synchronization error is as low as 10ns, and the efficiency test results are basically accurate.

Practical Application

For example, in the motor testing product of ZLG Zhiyuan Electronics, the MPT motor testing system, the above-mentioned synchronous measurement solution is used. Through this method, the synchronous output performance parameters and efficiency values ​​of the motor and drive can be obtained in real time, which is very helpful for users to effectively analyze and utilize the data.