Modelling and analysis of a low cost Brushless DC motor drive

This paper presents a buck converter based modelling technique for Brushless DC (BLDC) motor drives. The proposed technique is a better alternative to model BLDC motor drives due to its reduced computational complexity in contrast to the conventional phase-variable model. Using the model, constant speed operation of a BLDC motor drive operated without a DC link capacitor is analysed. Theoretical behaviour of the motor drive, predicted from the model, is compared with Matlab/Simulink based simulations to demonstrate the validity of the model. Mathematical expressions are derived from the model to evaluate the steady state performance of the BLDC motor drive, which is presented, in comparison to a similar sized conventional BLDC motor drive. The proposed model and mathematical expressions are expected to be useful at the design stage of the low cost motor drive to achieve comparable performance.