Induction machine equivalent network parameters computation from electrical and magnetic fields analysis

In this paper a numerical method suitable for analyzing the electric and magnetic dynamic behaviour in an induction machine at any operating condition is presented. Such study is carried out by using finite-elements method and the state variables approach. Since the iron permeability varies with time at any point and the currents in the windings are not a-priori known in the time domain, the dynamic behaviour of the machine was analyzed and the relations between voltage and current at unit terminals were deduced from the field equation. To carry out such analysis an induction machine was taken under investigation and, by neglecting the eddy currents in the conductors and the ferromagnetic non-linearity, net work parameters were computed both referring to the phase machine model and to the generalized machine mathematical one. Then the presence of the non-linearity and the mechanical equation were taken into account and the slip-torque characteristic was determined.