Study On Measurement System For Torque-Speed Characteristic Of Induction Motor

Recently, with the rapid development of the economy, the kind and quantity of motor increase fast, and the quality and performance standards for motor become more rigid. Higher-level measurement technologies are required for motor measurement. Aiming at measurement of the torque-speed characteristics, which is an important item of induction motor measurement, principle of DC electrical dynamometer was studied in this paper, and an automatic measurement based on DSP was designed.First of all, based on the detailed analysis of principle and stability of DC dynamometer, the paper presented a steady measurement scheme which bases on the tested induction motor, DC dynamometer and load resistance etc., and loads the induction motor by adjusting armature external resistance and excitation voltage. A measurement which can make the induction motor operation in the unstable portion of the torque-speed characteristic was proposed.Secondly, according to the measurement scheme, the method of direct measurement of stator torque and the method of photoelectric velocity measurement were respectively adopted to measure the torque and speed, and corresponding sensor sets and measurement circuit were designed. At the same time, a chopper controlled resistance and an excitation control circuit were designed.Thirdly, by using the TMS320LF2407A DSP as a core processor, PWM control, torque and speed measurement and current limiting protection etc. were realized, and an open-loop measurement system was constructed. In addition, a closed-loop control algorithm and structure were presented.Finally, experiments of the chopper controlled resistance and system were introduced. The experimental results demonstrate: the automatic measurement system which bases on the DC dynamometer and DSP can well measure torque-speed characteristic of induction motor.