LINE VOLTAGE BASED INDIRECT BACKEMF ZERO CROSSING DETECTION OF BLDC MOTOR FOR SENSORLESS OPERATION

P. Damodharan and K. Vasudevan

Keywords

BLDC motor, sensorless, backEMF, zero crossings, line voltage

Abstract

Brushless DC (BLDC) motors require a rotor position sensor for phase commutation. The rotor position sensors increases the cost and size of the motor as well as it makes the drive less reliable. However by detecting the back-EMF zero crossings position sensorless operation can be achieved. This paper describes a way to detect indirectly the back-EMF zero crossings from the three terminal voltages without using the neutral potential. Zero crossings of the diļ¬€erence of the line voltage waveform gives the zero crossing instants of the back-EMF waveform. Inaccuracies due to device drops have been eliminated. This scheme is simple to implement. Simulation results show the utility of this scheme for sensorless operation of BLDC motor. Hardware results validate the proposed indirect back-EMF zero crossing detection method.

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