A novel PWM scheme to eliminate the diode freewheeling in the inactive phase in BLDC motor

The BLDCM (brushless DC motor) with trapezoidal back-EMF (electromotive force) waveform is increasingly used. When the motor runs in the 120° conduction mode, two of the three phases are active and the rest phase is inactive at all times in principle. However, a ripple current occurs in the inactive phase due to the diode freewheeling during the noncommutation period in the traditional PWM methods, which aggravates the torque ripples. A new PWM method is proposed in the paper to eliminate the diode freewheeling during the noncommutation period in the inactive phase. As a result, the torque ripple is suppressed using the proposed method. The simulation and experimental results are demonstrated to verify the validity of the proposed PWM method.