Efficiency improvement of permanent-split capacitor motors in HVAC applications using a two-phase asymmetrical inverter

Permanent Split Capacitor motors are widely used in HVAC fan and pump applications less than 5 hp. These motors operate at efficiencies from 20% to 65%. These efficiencies can be increased if the motor is operated from a variable-frequency, variable voltage supply. However, application of power electronic controllers to realize the benefits of variable speed operation of these motors has generally been impeded due to a perceived lack of cost advantage. This paper presents a novel power converter based variable speed drive topology for the PSC motor, with appropriate dynamic efficiency control and a detailed evaluation of efficiency improvements. Simulation results that compare prior art in line-operated efficiency, and drive-operated efficiency are presented, illustrating that the proposed approach can result in efficiencies from 65% to 75%. The paper present a hardware demonstrations and simulation results.