The star-polygon brushless doubly-fed machine (SPBDFM) is a new type of wound-rotor machine and is attractive for variable-speed constant-frequency shaft generation system. The structure of rotor for the machine may be improving the conductor availability of the rotor windings. The kirchhoff laws is employed to illuminate the principle and some combinations of different slots and poles are presented as the examples. Harmonic analysis is also employed to analyze the magnetic motive force (MMF) waveform of rotor winding with the structure of star- polygon. Finally, the results are used to reveal that the SPBDFM is attractive for shaft generation system.
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