Torque Ripple and Loss Minimization of Trapezoidal Brushless DC Motor Drive by Harmonics Current Excitation Switching Technique

This paper describes torque ripple and loss characteristics of trapezoidal brushless DC motor (BLDCM) considering practical square wave current in. Extension to this, a simple 7
^th
harmonics current injection based optimized current switching with selective harmonics elimination scheme is proposed for improvement in torque ripple and motor efficiency. It is found analytically that 3
^rd
, 5
^th
, 11
^th
harmonics content does not contribute to the fundamental torque. These harmonics introduce torque ripple and extra losses whereas 7
^th
harmonics content enhances fundamental torque for both ideal and practical square wave current. Proposed PWM technique minimize motor losses as well as improves torque ripple. The effectiveness of new control scheme is explained through simulation based on PSIM 9.1.1. Finally, analytical outcomes are verified on 55W prototype BLDCM drive.