A 20 kW, 20 kHz unity power factor boost converter for three-phase motor drive applications from an unregulated single-phase supply

A three-phase, medium-power standard AC motor can be operated from a single-phase, highly-distorted and unregulated AC source by the use of a diode bridge rectifier/boost chopper/inverter cascade. The integration of a boost chopper unit employing an inductor made of amorphous metal (Metglas) into the system results in unity power factor at the AC supply side, low harmonic content line currents and high efficiencies and power densities. Laboratory and field test results have shown that this system constitutes a reliable, cost-competitive and almost maintenance-free alternative to other drive options, especially for auxiliary systems in electric locomotives where squirrel-cage induction motors are chosen as auxiliary driving machines.