Novel winding and core design for maximum reduction of harmonic magnetomotive force in AC motors

The familiar method for reducing the space harmonic content of the magnetomotive force (MMF) produced by a distributed polyphase ac winding is by chording, although by itself this can eliminate only one of the major low-order harmonics. Other techniques are available that can further reduce the harmonic content, although these all require a more complex winding arrangement. This paper presents a novel approach by which the winding harmonics can be even further reduced. In addition to altering the winding layout, the method employs an unconventional slotting pattern. The layout and the slot layout are both optimized to produce an MMF distribution that contains fewer harmonics than any conventional arrangement, while still preserving a high fundamental winding factor. The paper presents an example of the new technique in the design of a squirrel cage induction motor, and compares important features of the design with those of a standard machine. It summarizes the advantages and disadvantages of the novel approach.