Patent ID: 6154378
Filing Date: 2000-11-28
Classification: H02M

Abstract:
A polyphase AC-to-AC inverter for driving a potentially unbalanced polyphase load having a load neutral terminal from a wye-connected AC voltage source having a least three-phase output terminals and a source neutral terminal, said inverter comprising:rectifying means, coupled to said at least three source phase output terminals, for producing direct voltage across a direct-voltage bus;inductor means, interposed between said AC voltage source and said direct-voltage bus, for preventing alternator zero sequence current and isolating any harmonic currents of said AC voltage source;a polyphase switching bridge circuit coupled across a harmonic-isolated portion of said direct-voltage bus, for generating polyphase voltages at each of at least first, second, and third output terminals, each directly connected to said load, by switching said direct-voltage at a switching frequency at least one order of magnitude greater than a fundamental frequency of the polyphase voltages at said switching bridge circuit output terminals;a capacitance bridge coupled across said direct-voltage bus, for conducting switching currents from said switching bridge, and having a center tap coupled to said source neutral terminal, said capacitance bridge being effective to allow conduction of high-switching-frequency components of load current but substantially preventing conduction of fundamental-frequency load current component; andneutral inductor means, coupled via a conductor between said load neutral terminal, said source neutral terminal, and said capacitance bridge tap, for conveying unbalanced fundamental-frequency currents from said load.