Abstract: Brushless dc motor has permanent magnets which rotate around fixed armature. The current in armature rotates as it is electronically commutated. The commutation angle errors reduce the performance and overall efficiency of the motor. The novelty of the work is reducing commutation errors that are obtained based on the relationship between commutation point phase shift and the difference of dc-link current. Based on these relationship analysis is made under ideal, advanced and delayed commutations. The self-compensation method of commutation instant deviation delays the commutation angle by 10º thus eliminating the impact caused by commutation ripple thereby improving dynamic performance and control. The dc-link current difference decrease gradually and phase deviation converges to adjust the commutation angle. The proposed correction method can achieve ideal commutation effect thereby attaining fast convergence speed, current and torque.
Keywords: Brushless DC motor, Commutation signal deviation, dc-link current, Phase shift circuits, Sensorless control.