COMMUTATION TORQUE RIPPLE REDUCTION IN BLDC MOTOR

Abstract

Brushless DC motors are used in many applications because of their high efficiency, less maintenance, and long lifespan. However, one of the main disadvantages of the BLDC motor is its torque ripple. Due to this ripple, there will be more noise and vibrations, less efficiency, and less lifespan. To resolve this issue, researchers have provided many techniques. One of the Techniques is to boost the voltage during the commutation, which can help to reduce the Torque ripple in the machine to run it smoothly. During the commutation, the voltage applied to the motor is switched from one phase to another to have a continuous attraction force. So that the motor will rotate continuously, by increasing the voltage above the rated voltage, we can reduce the current ripple in the machine, which will reduce the torque ripple in the machine. Due to the finite inductance of the motor, commutation requires some time to rise and fall of the currents. Differences in the time of the falling and rising currents due to the freewheeling action and Back EMF will cause a ripple in the torque. It is found that by injecting more voltage during the commutation, this torque ripple can be reduced. Simulation has been done using the 2-level inverter and the voltage modifier circuit to reduce the torque ripple. Falling and rising current slopes and time are calculated to know how much time we need to apply the modified voltage. By using this method, there will be minimal impact on the efficiency of the machine. Implemented Hardware for controlling the speed of the BLDC motor using the spartan3E FPGA board. Here Proportional integral controller is used for controlling the speed of the machine. The PI controller will receive Feedback from the speed calculated from the hall sensor signals and reference speed provided. Based on the error between the reference speed and the actual speed, the PI controller will set the pulse width division Modulation (PWM) duty cycle to control the motor speed. The FPGA is used to generate the PWM signals, measure the speed and current, implement the PI controller, and display the speed and duty cycle. FPGA offers many advantages for implementing the speed-controlling algorithm. Mainly it can perform high-speed parallel processing and enable real-time control. Hardware implementation of PI controller in FPGA gives a faster response.