polumschaltbare drehstrommaschine through polamplitudenmodulation switchable symmetric ständerwicklung

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.