An Analysis of Solid Rotor Machines Part IV. An Approximate Nonlinear Analysis

One of the most important problems in the theory of rotating electric machinery is that of accounting for saturation effects. This paper adapts the results of the analysis of eddy current effects in semi-infinite solid saturated iron to develop the high-frequency operational and equivalent circuit impedances of a solid rotor machine. Parts I, II, and III of this series have presented a development of the basic theory, an investigation of the effects of curvature and a consideration of end effects, respectively. 1-3 Another paper has investigated the effects of field leakage. 4 This paper utilizes the electromagnetic model of Part I, neglecting the minor effects of curvature and finite length, except that the rotor iron is assumed to have a rectangular saturation curve.1 With the aid of this model, operational-and equivalent-circuit impedance equations are developed for conditions with relatively high-frequency eddy currents wherein the air gap fields are essentially one dimensional. Per-unit numerical data are given which illustrate the theoretical effect of saturation in increasing the resistive rotor impedance components over those obtained from a linear analysis.