A rapid method of analysing the m.m.f. wave of a single or polyphase winding

The usual method of evaluating the harmonic components of the m.m.f. wave of a polyphase winding is to perform a Fourier analysis. This can, however, be a long and tedious process, especially for stepped waveforms, and further it is common practice to perform the analysis for two limiting current-vector positions, to provide a check on the results. The method described here is exceptionally simple to apply, and makes use of the well-known standard winding factors. It is shown that, by simple substitution, the magnitudes of the Fourier fundamental and harmonic components of the m.m.f. in the air-gap can be found directly, although no indication is given of their relative phase angles. The mathematics of the proof has been fitted as closely as possible to the conditions prevailing in a real machine winding, whilst at the same time maintaining generality of treatment. The value of the method is exemplified in the last Section of the paper, by carrying out the analysis for an m.m.f. wave of some complexity. The ease of the method is at once apparent.