Motor testing details that cannot be ignored—control accuracy

    Traditional integrated manufacturers mainly build test platforms through simple instrument combinations. Due to the lack of in-depth understanding of measurement principles and R&D experience, it is difficult to provide comprehensive functional customization services according to customer needs. With its in-depth understanding and long-term accumulation in the fields of power analysis and motor measurement, Zhiyuan Electronics has integrated the concepts of instrument design and system integration to launch the epoch-making MPT intelligent motor test and analysis system, which has achieved a comprehensive innovation in the motor test system in terms of control accuracy, analysis capabilities and international standard support. It is used to meet the deep-level requirements of different industries for motor testing and realize more professional and user-friendly functional customization services.

    Next, let’s discuss a detail indicator that is easily overlooked in the motor test platform: control error.

Control error of traditional motor test platform
    Traditional motor test platform only performs open-loop control on motor speed and torque, ignoring the errors introduced by the fixture and motor load, and cannot provide users with accurate motor measurement results.

Figure 1. Architecture of a traditional motor test platform

Causes of Errors
    The reasons for the speed and torque errors in the motor test system (dynamometer) can be summarized as the following three points:
1. In the motor drag system, when the torque output by the motor is transmitted to the sensor or load through the fixture, a small part of it will be lost as friction torque. Therefore, in order to drag the load normally, the motor will output a torque slightly larger than the load, causing an error between the torque measurement value and the set value;
2. There is a control error in the motor load itself, and the control signal does not completely match the actual load torque;
3. Since there is a functional relationship between speed and torque, the above two errors will also affect the speed.

Figure 2 Causes of error

How to ensure the high control accuracy of the motor test platform?
    ZHIYUAN Electronics MPT motor test system adopts advanced intelligent PID control architecture. It consists of three parts: professional motor test software MotorTest, motor operation module and high-precision power analyzer to form a closed-loop feedback system. The motor speed and torque control accuracy is as high as 0.5%, providing users with the most accurate motor performance analysis.

    During the test, the high-precision power analyzer measures the motor's speed and torque in real time, and uploads the data to the MotorTest software to compare the test data with the set values. If there is a deviation between the two, the system control module will perform negative feedback adjustment on the motor's speed and torque, and then perform sampling and comparison again until the test data is consistent with the set values ​​within the accuracy range. Only then will the system test and analysis begin to truly present the motor performance.

Figure 3 MPT motor test system architecture

Take the
    motor characteristic curve test as an example: when the user sets the torque to 10~100N•m, the deviation of the traditional motor test platform is as high as 5%, while the torque control error of the MPT motor test system is as low as 0.36%, meeting the user's needs for accurate analysis of motor characteristics.