A Fast and Direct Analysis of Three-Phase Induction Motors Using Finite Element

Abstract

A new finite-element technique for squirrel cage Induction Motor features analysis is presented in this paper. Motor performances are directly predicted performing on-load test simulations, in several working points. The finite-element analyses are carried out imposing both stator and rotor currents. Thus, only magnetostatic simulations are needed to get the electromagnetic quantities, such as torque and slip. Saturation phenomena can be considered in any operating conditions under load, with short computational time. In each motor working point, a very fast finite-element procedure, closely linked with the analytical machine model, is used to catch the proper current distribution in stator and rotor slots. It allows the motor performances to be predicted without the preliminary knowledge of the machine equivalent circuit parameters. Experimental tests are carried out and reported in order to verify analysis results.

A Complete and Fast Analysis Procedure for Three-Phase Induction Motors Using Finite Element, Considering Skewing and Iron Losses

“…A useful trick is considering a three-phase rotor equivalent winding sinusoidally distributed in the rotor slots, in order to properly set the rotor current and compute the rotor flux linkages. The complete procedure to design such a winding is described in [8]. For low rotor frequencies, the rotor bar current distribution can be considered uniformly distributed.…”

“…The relationship (8) represents another peculiar feature of this model: the rotor current vector acts only along the q-axis of the RFO reference frame. This condition represents an advantage to create a static finite-element model of the machine.…”

“…In this reference frame, the stator current is imposed. From the analytical model, the rotor current has to be set along the q-axis and the amplitude has to follow the rule (8).…”

“…The condition (8) is related to the model feature λ rq = 0. So, the proper rotor current amplitude is set when the rotor q-axis flux linkage is equal to zero.…”

“…These features are included in the method described in [8]; in this paper some improvements to the MS IM analysis are introduced together with practical application examples.…”