Developments in Speed-Changing, Single-Phase Induction Motors

Further development of single-phase, pole-changing motors based on the logic of pole-amplitude modulation are reported. The principles of preshaping and asymmetrical modulation have been extended to the single-phase motor, the former resulting in reduction of number of terminals from 12 to 6, while with the latter, the pole- amplitude modulation logic can be applied to any set of pole combinations. The versatility of this method is enhanced by extending it to the case of asymmetrical phase windings, resulting in 3-speed machines, which can be started as normal single-phase machines at any of the three speeds.