Nonlinear Modeling of Air-Gap Flux Density Distribution in a Synchronous Generator with Magnetic Saturation

Abstract

A nonlinear model is proposed which represents air-gap magnetic flux density distribution in a synchronous generator with magnetic saturation. In order to express the effect of saturation in a generator, the authors have measured air-gap flux in specially designed synchronous generator which shows magnetic saturation in the field pole iron cores. In the generator, the total amount of air-gap flux is affected by the saturation of field cores, but the waveform of flux distribution is not affected by the saturation. Therefore we deal with the air-gap permeance and saturation in the field pole cores, separately. By regarding the saturation as a demagnetizing m. m. f. due to a fictitious winding, we construct a magnetic circuitt which represents the flow of magnetic flux inside the generator, and derive an expression for air-gap flux density distribution. Good agreement is obtained between the theoretically calculated results and the measured results by using search coils placed at the teeth of the armature.