Commutation Torque Ripple Comparison in Cuk Converter Fed Brushless DC Motor Drives with Mode Switching Selection Circuit

Comparative study on the torque ripple reduction during commutation period of Cuk converter fed BLDCM using mode switching selection circuit is done with current controlled BLDCM drive.H-PWM-L-PWM called modified bipolar PWM method shows superior performance in high speed BLDCM(Brush-less DC motor) drives when compared with other PWM methods.Torque ripple reduction during commutation period can be done by maintaining constant current in the non-commutated phase at low speeds using appropriate PWM methods.However the PWM methods used in low speed BLDC drives fails in reducing the torque ripple at high speeds due to the finite value of inverter input voltage.BLDC motor drive using Cuk converter with mode switching selection circuit provides effective way of commutation torque ripple reduction at high speeds.The method uses mode switching selection circuit,consisting of an additional switch and diode,to vary the voltage output of the Cuk converter during the commutation period to provide raised voltage at the three-phase inverter input.The method can adequately dwindle the torque ripple during commutation over all speeds, avoiding the changeover of modulation methods, resulting simpler modulator design.H-PWM-L-PWM(modified bipolar PWM)method for switching inverter during both conduction as well as commutation period together with Cuk converter and mode switching selection circuit will combine the advantages of both methods.MATLAB/SIMULINK environment is used to carry out the simulation and comparative studies to verify the effectiveness of the commutation torque ripple reduction method.