Speed-Changing, Single-Phase Induction Motors with Single-Layer Windings

Low-output, single-phase machines usually have single-layer windings and in this paper an attempt is made to extend the application of the pole-amplitude modulation method of speed changing to this class of machine. It has been shown that 2- and 3- speed induction motors with independent starting at any of the speeds are possible with single-layer windings. In all, only two different sizes of coils will be required for any pole combination, though a single size of coil will suffice in windings where uniform coil-side group distribution is adopted for the initial pole number. Test results for a few cases fully support the theoretical conclusions.