18-pulse rectification system using a wye-connected autotransformer

A wye-connected autotransformer comprising:

• three sections each spaced 120° electrically apart, wherein each section comprises:
• a main winding having a neutral end and source end, wherein the neutral end is connected to a floating neutral point and wherein the source end is connected to one phase of a three-phase power source;
• and
• a pair of phase shift windings, wherein each phase shift winding comprises a second winding and a third winding connected in series, wherein one end of the second and third windings is connected to the source end of the main winding and wherein an other end of the second and third windings is a phase of the wye-connected autotransformer that is phase shifted +/−40° electrically from the source end,
• wherein each main winding has a same first number of turns, each second winding has a same second number of turns, and each third winding has a same third number of turns, and wherein a ratio between the first, second and third number of turns is about 1:0.137:0.605, respectively.

A wye-connected autotransformer comprising:

• three sections each spaced 120° electrically apart, wherein each section comprises:
• a main winding having a neutral end, a central tap and an output end, wherein the neutral end is connected to a floating neutral point, wherein the central tap is connected to one phase of a three-phase power source, and wherein the output end is a phase of the wye-connected autotransformer;
• and
• a pair of phase shift windings, wherein one end of each phase shift winding is connected to the central tap of the main winding, an other end of each phase shift winding is a phase of the wye-connected autotransformer that is phase shifted +/−40° electrically from the output end, and a voltage boost occurs from said one end of each phase shift winding to said an other end of each phase shift winding,
• wherein each main winding has a same first number and a same second number of turns as determined by the central tap and each phase shift winding has a same third number of turns.