A STUDY ON TORQUE PULSATION IN BRUSHLESS DC DRIVES

Abstract

Brushless dc motors are increasingly popular for direct drive applications which result in tremendous elimination of mechanical interfaces and better system performance. However, such applications exhibit torque pulsation problems for their low speed operations. This projects seeks to study the effects of machines parameters on torque pulsations of a permanent magnet motor driven in a brushless dc drive configuration. A model is presented to describe the entire drive system. The machine is represented by its equivalent electrical circuit and the torque equations are derived using the co-energy equations. A set of mathematical equations are derived to simulate the response of the machine. Second, a simulation package is used to simulate the machine and the control circuits. The model is validated under different operating conditions. Based on the validated model, the effects of machine parameters are discussed in detail. Torque pulsations are divided into three main groups based on the contributing parameters. Contributions and significance of each torque component are analysed. Finally, a torque pulsation minimisation method is proposed and investigated. Experimental results are evaluated and the effectiveness of the method are proven.