Experimental investigation on sensorless starting capability of new 9-slot 8-pole PM BLDC motor

Abstract

The capability of new 9-slot 8-pole permanent magnet BLDC motor to start without position sensor is investigated in this paper. The permanent magnet rotor influences the stator windings inductance as the rotor position changes. It leads to variation of motor current. Sensorless control of BLDC motor usually uses back EMF method, but this method cannot be used from standstill, since there is no back EMF. To start this motor smoothly from standstill, the rotor position can be estimated using inductance variation method by injecting high frequency low current to the stator windings. The new 9-slot 8-pole PM BLDC motor has the advantage of its asymmetrical windings. It generates unique current responses when injected by sinusoidal high frequency current on different rotor positions. The current responses then can be separated by fuzzy logic algorithm to determine the rotor position. The experimental results of the estimated rotor position sector with the experimental system are shown in this paper. From these results, the sensorless starting using inductance variation method is applicable to the 9-slot 8-pole motor.