Abstract

A three-phase ac power inverter incorporating circuits which operate to correct input power factor to near unity when connected to an ac input rectifier, while also reducing input harmonic distortion. The inverter includes a dc capacitor connected between buses, and three, four-pole inverter H-configuration bridges which output ac phases A, B and C. The cross-bar of each H-bridge is made up of an L-C filter. The inverter bridge switches, switching in an output Pulse Width Modulation mode for generating three phase sine waves, also serve to pump resonant energy between the L-C filter in each bridge and the dc capacitor. Phase A, B and C inverter bridges are pumped at the same carrier frequency, providing a continuous feed to the dc capacitor and the input rectifier. In effect, this action extends the conduction angle of the input rectifier, resulting in the input power factor being corrected to near unity. The pumping action through the L-C filters also filters and reduces the input harmonic distortion.