| 摘要 |
The invention provides improved stator windings for pole-amplitude modulation (P.A.M.) pole-changing electric motors and generators. In large machine of high pole-numbers, the effect of adjacent harmonics of m.m.f. waveform becomes evident in the form of low-frequency vibration of the frame. In small machines the effect, although present, is less important. The invention provides stator windings, particularly for large machines, wherein the phase-winding coil grouping, selected primarily for sinusoidal modulation, is selected secondarily to include a third-harmonic content, whereby the adjacent harmonic m.m.f. content may be reduced for both alternative pole-numbers.
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