Induction machines with novel concentrated windings

Torque ripples can reduce precision control and increase vibration and noise in electric vehicles, servo systems, and wind generators. To address this problem, two novel winding methods are proposed. In one method, three-phase coils are wound around each tooth, with each coil having a different number of turns around a given tooth. In the other method, coils with as many phases as stator teeth are arranged in the stator slots. Furthermore, these multi-phase windings allow an induction machine to change the number of its poles. The proposed winding schemes may be applied also to toroidal windings. The characteristics of machines with these proposed windings are examined using numerical magnetic analysis. The results show that torque ripple can be reduced by approximately one quarter that for conventional windings for four-pole machines using both concentrated and toroidal winding schemes. These proposed winding schemes are shown to reduce torque ripple significantly.