Patent ID: 8730686

Claim:
A dual-input nine-phase autotransformer comprising: a first plurality of coils A 0 -A 6 wound on a first phase leg of the autotransformer, each coil A 0 -A 6 defined, in part, by a number of winding turns associated with the coil; a second plurality of coils B 0 -B 6 wound on a second phase leg of the autotransformer, each coil B 0 -B 6 defined, in part, by a number of winding turns associated with the coil; a third plurality of coils C 0 -C 6 wound on a third phase leg of the autotransformer, each coil C 0 -C 6 defined, in part, by a number of winding turns associated with the coil; a first plurality of input terminals In 1 , In 2 , In 3 connected to provide a first three-phase AC input to the first, second and third plurality of coils; a second plurality of input terminals In 4 , In 5 , In 6 connected to provide a second three-phase AC input to the first, second and third plurality of coils, wherein the second three-phase AC input has a magnitude less than the first three-phase AC input; a plurality of output terminals Out 1 , Out 2 , Out 3 , Out 4 , Out 5 , Out 6 , Out 7 , Out 8 , and Out 9 connected to the first, second and third plurality of coils for providing a plurality of AC output voltages; and a plurality of internal terminals T 1 , T 2 , T 3 , T 4 , T 5 , T 6 , T 7 , T 8 , and T 9 for connecting the first, second and third plurality of coils in a configuration that provides a desired 40° phase shift in the AC outputs provided at the plurality of output terminals Out 1 -Out 9 , respectively, and provides a constant AC output voltage regardless of whether the first AC input is provided at the first plurality of input terminals In 1 , In 2 , In 3 or the second AC input is provided at the second plurality of input terminals In 4 , In 5 , In 6 ; wherein the number of winding turns associated with coils A 0 -A 6 , B 0 -B 6 , and C 0 -C 6 are defined by the following table of ratios scaled to a number of winding turns n 0 associated with coils A 0 , B 0 , and C 0 : Coil Number of turns A0, B0, C0 n 0 A1, B1, C1 n 1 = 1.638 * n 0 A2, B2, C2 n 2 = 6.725 * n 0 A3, B3, C3 n 3 = 2.638 * n 0 A4, B4, C4 n 4 = 2.578 * n 0 A5, B5, C5 n 5 = 2.578 * n 0 A6, B6, C6 n6 = 0.5 * n 0 .