Generator operations of saturated induction machines

Abstract

This paper shows that, due to the saturation of the main magnetic circuits, the generator behaviour of induction machines may not be evaluated theoretically with accuracy by means of traditional mathematical models, especially when operations at variable frequencies are dealt with. For this reason the paper presents a mathematical model of saturated machines. Voltage and current space vectors are used. The model has been carried out on the basis of two air-gap machine inductances (one differential and the other rational) previously introduced by another author (Kovacs, 1984). It has been validated at steady state by comparing the theoretically evaluated and experimentally measured armature currents of a mass-produced machine. The influence of saturation on armature current amplitudes is evidenced by comparing numerical results obtained by the suggested model with those of a traditional model. The model is also used for the performance analysis of dynamic and steady-state generator behaviour of cylindrical induction machines and for carrying out conditions that obtain self-excitation and stable operations of machines supplying passive electrical networks.