Three phase inverter power supply with balancing transformer

Claim 1

A multiple phase inverter with a neutral comprising: a plurality of pairs of phase switches, each pair of phase switches being connected in series between first and second reference potentials, each switch being switched between conductive and nonconductive states; a plurality of outputs each respectively coupled at a junction between a different pair of the plurality of pairs of switches; means for causing each switch of a pair of switches which is coupled to one of the first and second reference potentials to be conductive for an interval and for causing at least one other switch of one of the other pairs of switches which is coupled to the other of the first and second reference potentials to also be conductive during the interval to provide a path for current between the switches without a neutral connecting the conductive switches to the load; a filter having a plurality of inputs coupled respectively to a different one of the outputs and forming the neutral, the filter shunting frequency components above a fundamental frequency determined by a switching rate of the pairs of switches to the neutral and providing a plurality of different phase outputs at the fundamental frequency; a multiple phase transformer having a plurality of windings coupled in a wye configuration with a first terminal of a plurality of inputs respectively coupled to a different one of the plurality of phase outputs and a second terminal of the windings coupled to the neutral and a phase output coupled to each of the windings, the transformer having a secondary with a plurality of secondary windings connected in a delta configuration; and wherein the phase outputs of the transformer each respectively are for connection to a separate phase of an unbalanced multiple phase load.