The application of the method of images to machine end-winding fields

Abstract

Although a variety of methods have been used to calculate the fields associated with the end-windings in rotating electrical machines, there appears to have been little attempt to exploit the method of images. This provides a means of solving the field problem by integration with relatively high accuracy. By making use of the vector potential, a comparatively simple calculation is possible of the flux linkages due to complex end-winding arrays. The image principle is extended in the paper to circuits which are partly embedded in the reflecting surface. The effects of various complexities in the boundary conditions, including the presence of the air-gap, are considered. The method is well suited to both turbo-type alternators, with magnetic and non-magnetic end-rings, and to induction motors. It is illustrated by calculating the end-winding inductance of a 2-layer induction-motor winding.