Sensorless Control of BLDC Motors Based on Variation Behavior of Winding Inductances

In brushless DC motors(BLDCM) with a saliency pole structured rotor,influenced by saliency effects,the self-inductance and mutual-inductance present periodicity sinusoidal variations,which results in the regular changes of terminal voltage waves of three phases during the unexcited period.Starting from this feature,the paper analyzed the variation behavior of the terminal voltages of the unexcited phase in each PWM chopping period,and expounded the estimation of commutation position at the running state using the character.Combined the method with saturation effects of the iron core,the paper raised a new method of rotor position interval estimation at the stationary state.Experimental results show that the method can reliably estimate the rotor position at the running and stationary state with a small error.