Influence of PWM modes on non-commutation torque ripple in brushless DC motor control system

Brushless DC motor has large torque ripple for the design and characteristic of the control strategies. The torque ripple can be divided into commutation torque ripple and non-commutation torque ripple. This paper analyses why the non-commutation torque ripple produced in detail, points out the brushless DC motor can cause the diode freewheeling of inactive phase and non-commutation torque ripple when using the existing PWM modulation mode. According to the method of PWM_ON_PWM modulation mode, the result shows that it can reduce non-commutation torque ripple. But the method also can bring out new problem, the brushless DC motor need to commutate every 30 electrical angle. This paper uses the digital chip-TMS320F2812 to control the commutation time. The result shows the brushless DC Motor modulation can decrease non-commutation torque ripple effectively.