Effect of BLDC motor commutation schemes on inverter capacitor size selection

With the increase in cost and size constraints from electronic devices, bus capacitor sizing becomes a significant factor for the inverter design. Square wave current generation, using only one current sensor in the dc bus link, is a low cost and reliable current control strategy for brushless dc motor drives. This paper analyzes the bus capacitor selection criteria from ripple current, ripple voltage, energy balance and operating life perspectives. Different commutation techniques have been discussed and the capacitor selection criterions have been analyzed for the commutation schemes. Computer simulation with a 1/2 kW motor-inverter system have been performed to compare the ripple currents, ripple voltages and operating life of the inverter bus capacitance under different commutation techniques.