Distribution Factors and Pitch Factors of the Harmonics of a Fractional-Slot Winding

The investigation of the fractional-slot windings with respect to their harmonic (differential) leakage, to noise, and so forth, requires the knowledge of the distribution factors of their harmonics. Very valuable work on distribution and pitch factors of fractional-slot windings has been done by J. F. Calvert.¹ On the basis of charts he worked out distribution-factor tables covering the actual harmonics up to the 24th. Once the chart of the winding has been set up, a simple formula can be used for computing the distribution factors of the harmonics for any three-phase fractional-slot winding. In the following paper, simple formulas are derived for the distribution factors of the harmonics of fractional-slot windings which make the layout of charts unnecessary. These formulas are similar to those of the integral-slot windings. In deriving them the usual method of attack, namely, the use of charts, had to be abandoned and the vector diagram of the different slots used instead.