Patent ID: 7233506

Claim:
A multipulse AC to DC converter system comprising a three-phase regular polygon auto-connected transformer having at least five coils on each phase; with at least three coils combining to produce a long side of the polygon; with at least two coils with a center tap combining to produce a short side of the polygon; with alternate long and short sides of each of three phases being serially connected with other phases to form a three-phase polygon magnetic circuit structure; with three symmetrically disposed points of connection to said coils on each phase each being connected to one of three input phases; with said symmetrical points including the center of the short sides of the polygon; with the points of interconnection of each coil providing junctures such that m three-phase output voltage sets each displaced by 120 phase are available, with some of said voltage sets having a phase shift relative to the three-phase power source; with such phase shift being determined by the number of coils and relative number of turns on each coil; with the phase shift being suitable for powering multiple three-phase converters in a manner to provide DC output with reduced ripple voltage and reduced harmonic current from the three-phase AC supply; with nominal phase shifts including, but not limited to, ±7.5°, ±15°, ±20°, ±22.5°, ±30°, ±40°, ±60°; with inductors connected in series with output leads of the transformer as necessary to balance and/or augment the inherent transformer leakage inductance in a manner to reduce possible circulating currents and increase the current conduction angle of the current flowing in each output lead; with such combinations of m phase-shifted sets of three-phase voltage being suitable to power m three-phase converters comprising controlled or uncontrolled rectifier devices to produce an AC to DC converter with reduced output voltage ripple and low harmonic content.