A low cost drive for three-phase operation of Brushless DC motors

This paper presents a novel drive topology that allows three-phase operation of Brushless DC (BLDC) motors without an intermediate DC link capacitor. The proposed motor drive uses a unique six-step Pulse Width Modulated (PWM) switching algorithm to facilitate three-phase operation of the BLDC motors. The proposed drive system is modelled using Matlab/Simulink with SimPower Systems toolbox for a 320 W BLDC motor. With the proposed unique switching algorithm, the motor can be operated either in speed control or electromagnetic torque control mode. The paper explains the derivation of the switching algorithm, and illustrates the Matlab/Simulink model, which is used to validate the drive system by simulations. Simulated results indicate that the theoretical performance of the proposed drive system is comparable to existing techniques. In addition, the proposed drive system is simple to implement and low in cost without an intermediate DC link capacitor. Thus the proposed topology would be an attractive alternative for low cost BLDC motor drives, where the torque ripple is not a concern.