Patent attributes
A multiple-winding induction machine may be used to obtain a reduced-speed-variation electric drive when using a variable-frequency power distribution system. Each winding may have a different number of poles. The winding with the smallest number of poles may operate the machine at the lowest bus frequency, while the winding with the largest number of poles may operate the machine at the highest bus frequency. In one embodiment, a third winding, with a middle number of poles, may operate the machine at the middle frequency ranges. The speed of the induction machine is a function of the electrical frequency and the number of the winding poles. Therefore, the operating speed range can be reduced by switching from one winding to another. According to the present invention, windings with different numbers of poles can be designed to achieve different reductions in speed variation.
