A comparative study on approaches to curve fitting of magnetization characteristics for induction generators

Abstract

The curve fitting of magnetizing characteristics of self excited induction generators (SEIG) resulting airgap voltage (Vg) with magnetising current (Im) is crucial for performance analysis of such machines using design tools. The magnetisation characteristic may be obtained using the B - H curve of the core material. An appropriate curve fitting technique/regression analysis is employed to represent Vg - Im curve from which Vg - Xm curve can be derived. There is wide literature on approximation of magnetization curves of variety of materials. Accurate analysis of a magnetization curve, or the B - H characteristic, has always posed problems for electrical engineers dealing with machine design. The problem has been to find a single function to represent the wide range from the origin to saturation with a minimum error over the whole range. Moreover, such a function should be mathematically simple for easy application. In this paper, different techniques are critically compared to guide the designers on a right approach with special reference to SEIG.