This paper describes a new inverter that efficiently controls the speed of conventional PSC (permanent split capacitor), single-phase motors that drive fans, pumps, compressors, and other components found in home appliances. The inverter supplies a variable-frequency, single-phase output. A unique feature of the inverter is it can provide a higher voltage to the capacitor leg of the motor than to the main winding, which enhances motor torque for starting and low-speed operation. The new inverter has several important advantages over conventional approaches to speed control for residential appliances. It provides large energy savings and lower motor temperatures compared to conventional TRIAC or multiple-tap speed controls that are now used with PSC motors. In addition, the inverter eliminates the need for three-phase motors, DC motors, or other special motors used with conventional electronic drive systems. The ability to use standard single-phase motors reduces inventory costs. It also allows for operation without electronics, which simplifies servicing and improves reliability.
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