Non-harmonic analysis of asynchronous machine based on a model with discrete space distribution of the air gap magnetic permeance

摘要

The paper presents a new non-harmonic model of an asynchronous machine derived under the assumption that the magnetic permeance of the air gap has discrete space distribution along the circumlierence of the machine and that magnetic flux can flow between the stator and rotor only through the finite number of stationary and rotating points (the so-called magnetic channels) corresponding to the axes of stator and rotor teeth. As a result of such an assumption, stator-rotor inductances as a function of rotor angle are expressed by piecewise-constant functions. This creates a simple mathematical model of a machine consisting of a system of linear differential equations with time-constant coefficients and one algebraic equation. They are solved alternately step by step in open intervals in which stator-rotor inductances are constant and at the edges of the intervals. This method is convenient in computer calculations of transient and steady states of asynchronous machine and enables the influence of the number of stator and rotor slots on the behaviour of amotor to be considered. The results of computer simulations of starting characteristics as well as of steady-state torque-speed curves for machines with different numbers of magnetic channels are presented.