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JEET, Vol. 12, No. 5, September 2017
A New Three-Phase Current Modulation Method to Suppress the Commutation Torque Ripple of Brushless DC Motor
Tiehua Ma
Area B - Electric Machinery and Power Electronics
Abstract The brushless DC motors commutation torque ripple is caused by inconsistency in the rate of phase current change. Thus, a method that considers armature resistance is proposed to modulate phase current. The three-phase control strategy, which involves the open-phase conduction, off-phase pulse width modulation, and maintained non-commutation phase technique, is applied during commutation at full-speed segments of the motor. Changes in each phase current are analyzed theoretically by establishing mathematical model based on phase current to determine the relative difference among shutdown phase, duty, and motor operating parameters. The turn-on and turn-off phase current change rates are made to be consistent to ensure less non-commutation phase current ripple, then the torque ripple is inhibited. The simulation results show that the phase commutation current and torque ripple coefficient of the proposed method are reduced from 56.9% and 55.5% to 6.8% and 6.1%, respectively. In the experiment system, the pulsation coefficient of the motor phase current is reduced from 40.0% to 16.7% at low speed and 50.0% to 18.8% at high speed. The simulation and experimental results show that the proposed control method significantly inhibits commutation current and torque in the full section.
Keyword Brushless DC motor,Commutation torque ripple,Current control,Armature resistance
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