Improving the Efficiency of Аlternating-Current Machine Windings

Abstract

The properties of a magnetic field that the current of a three-phase winding of the starter of an induction motor generates greatly depend on winding type. The smaller the quantity of higher (parasitic) harmonics with respect to the fundamental (working) harmonic in the curve of magnetomotive force, the greater the winding efficiency. Three-phase six-band windings have become widespread. Increasing the number of phases promotes a decrease in the quantity of higher harmonics, but a special six-phase supply source is needed for this. A three-phase combined 12-band winding is considered, the electromagnetic properties of which are close to the properties of a six-phase winding. Such a winding is compared to a standard six-band winding with respect to the differential scattering coefficient that characterizes the magnetic field on the basis of the content in it of higher harmonics. Two variants of windings were compared: with continuous and noncontinuous phase bands. The calculation results of differential scattering coefficients of windings for 24, 36, and 48 slots falling per pair of poles are presented. Calculation of the least theoretically possible differential scattering coefficient was performed for a combined winding with continuous phase bands. A high efficiency of combined winding with continuous phase bands as compared with standard winding and combined winding with noncontinuous phase bands was demonstrated.