Development of a Synchronous Generator Model founded on a Permeance-based Air-Gap Flux Density Analysis

Abstract

The magnetic flux inside a synchronous generator is regarded as a characteristic that dominates a generator operation. This paper develops a simple model of a synchronous generator by the use of which it is possible to estimate a air-gap flux as well as electrical characteristics easily. The air-gap flux density can be related with a permeance and a magneto-motive force (mmf) along its magnetic path by the Ampere's laws. These relations are adopted in this paper.
We practically estimate the distribution of the permeance along the air-gap and the mmf profiles of the stator and the rotor of 6kVA scaled-down tested synchronous generator. By the use of these estimated profiles, the relations among the air-gap flux, field current and armature current are represented by a linear equation system. Consequently, the static electrical and magnetic characteristics of a synchronous generator can be estimated by giving only field exciting voltage and load impedance. The distributions of the air-gap flux density and waveforms of the field and armature currents are simulated for various unbalanced-load conditions. The simulated results are well agreed with experimental ones not only for fundamental components but also for higher harmonic components. Therefore, our developed method based on the permeance profile is available to calculate the static characteristics of synchronous generators.