Safety Operation Area of Zero-Crossing Detection based Sensorless High Speed BLDC Motor Drives

Abstract

For zero-crossing detection based sensorless BLDC drives, long commutation freewheeling duration will increase the difficulty of zero-crossing detection and limit the sensorless safety operation area. In extreme cases, zero crossing of back EMF will not be discernable when the commutation freewheeling duration exceeds $30^{\\circ}$, causing the failure of sensorless drives. In this paper, the relation between the commutation freewheeling path and the PWM switching pattern is described. Besides, an iteration method for determining the safety operation area is presented. It demonstrates that a suitable PWM switching pattern can reduce the freewheeling angle and broaden the sensorless safety operation area.