Nonlinear Modeling of Air-Gap Flux Density Distribution in a Synchronous Machine with Magnetic Saturation in the Pole Tips

Abstract

A nonlinear model is proposed representing air-gap magnetic flux density distribution in a synchronous machine with magnetic saturation in the pole tips. In order to explain the effect of magnetic saturation in a synchronous machine, the authors have measured air-gap flux in a specially designed synchronous machine, and recently proposed a model for the air-gap flux density distribution, concentrating on magnetic saturation in the field pole iron cores. In this paper, we propose an adaptation of our model for calculating air-gap flux, specifically addressing the magnetic saturation in the pole tips. By regarding the saturation as a consumer of m. m. f. similar to a virtual winding, we construct a magnetic circuit which represents the flow of magnetic flux inside the synchronous machine, and derive expressions which represent air-gap flux density distribution. Close agreement is obtained between the theoretically calculated results, and the results measured using search coils placed at the teeth of the armature.