Influence and Compensation of Commutated Current Freewheeling for Sensorless Brushless DC Motor
Xi Cheng;Xin Nie;Nanjing Research Institute on Simulation Technique;
The terminal voltage is distorted by diode freewheeling current from phase current at the commutation moment of brushless DC motor(BLDCM). The distorted teminal voltage makes position detection signal phase ahead and deviate from the best commutation time when adopting the backEMF zero-cross detection method in sensorless position control. The advanced position signal increases the torque ripple and even causes commutation failure in the high speed, limiting the speed range of sensorless brushless DC motor. This paper analyzes the reasons of ahead position signal caused by diode freewheeling current. The relationship between the ahead phase, torque and speed is presented. The ahead phase is compensated according to the relationship. Finally, simulation and experiment results prove the effectiveness of this compensation method. BLDCM can still achieve stable operation under sensorless control with different load torque and speed.
【CateGory Index】： TM33