Novel arrangement of combined star-delta stator winding aimed at reduction of copper usage in electric machine

The submitted paper deals with the increased energy efficiency of induction machines by means of the so-called combined stator winding. Two basic variants of this winding, the series and parallel ones, are shown. The suppression of higher harmonics is analysed by means of the method of space vectors and symmetrical components. It is shown that the so-called series variant of the combined winding has a better ability to suppress higher spatial harmonics. The commonly used combined winding has, however, a longer pitch and thus bigger stator resistance and greater consumption of copper. The paper presents a proposal of an adapted combined winding whose pitch is smaller than that of the used three-phase winding. This fact results in decreasing the consumption of copper conductors with preserving the energy efficiency. The results of the analysis have been verified by measurements on physical models of machines with the combined and the adapted combined windings.