Simulation of induction machine operation using a step-by-step finite-element method

Abstract

In order to model the operation of an induction machine when space harmonics are neglected, the magnetodynamic model with the equivalent ac magnetization plot can be used. But when we want to simulate an induction machine with an open isthmus, for instance, the space harmonics cannot be neglected and a step-by-step method is a solution to modeling its action. In this paper, we develop a means of modeling an induction machine with a nonlinear step-by-step method. The motion of the rotor is taken into account through the displacement of its mesh. The basis of the method is that after each step of the simulation we rebuild only the air gap portion of the mesh. Applied to an industrial four-pole squirrel cage induction machine with an open isthmus, this method provides accurate values of the torque on the whole range of velocity. We have compared the curves obtained by this method with those by the magnetodynamic model for many different types of induction machines. Our method shows the effects of space harmonics on torque more accurately. The curves of torque at different velocities give us a lot of information on effects of harmonics.