Speed-Changing of Induction Motors by Phase Modulation

摘要

The principle of phase modulation is described and methods of design which enable speed-changing of induction motors to be achieved using six-lead changeover switching are developed. Comparison with the method of pole amplitude modulation (PAM) shows that the developed method is superior. The method of switching, however, requires three parallel-path connections for three-phase windings and this places practical limitations on their design. Nevertheless windings which, for constant-torque or constant-power close-ratio speed-changing, are to be preferred to PAM were designed. The methods of design are applied to a variety of pole-combinations. Trial machines for the popular pole-combinations of 8/10, 4/6, and 6/4 poles were built and tested. Their successful operation confirms the value of the application of phase modulation.