SIMULATION OF INDUCTION MACHINE OPERATION USING A STEP BY STEP FINITE-ELEMENT METHOD COUPLED WITH CIRCUITS AND MECHANICAL EQUATIONS

In order to simulate the operation of an induction machine supplied with sinusoidal currents, the complex magnetodynamic model associated with the equivalent AC magnetization curve can be used [1]. When using the circuits equations, it is possible to improve the model of induction machine in which the squirrel cage rotor is a polyphase circuit that includes connections of bars and end-rings, stator coils are connected to their end-windings by external impedances and supplied by sinusoidal voltage sources [2]. If non sinusoidal sources are used, a step by step method associated with the motion of the rotor mesh is necessary [3]. Finally, the mechanical equation coupled with the step by step model gives the possibility to represent transient states [4]. In this paper, a model developed by the authors will be presented, in which the implementation of the circuit and the mechanical equations coupled with a step by step F.E. model is made. This allows the user to take into account the end-windings, the end-rings and the non sinusoidal voltage supply. Applied to an industrial 4 pole double-squirrel cage induction machine, with open rotor slots, this method provides accurate results on the torque values in the whole speed range. A simulation of the starting operation of this motor with sinusoidal voltage source shows the transient states of the stator currents and the resulting torque [5].