93_FE_converotrfed - IEEE TRANSACTIONS ON MAGNETICS, VOL....

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IEEE TRANSACTIONS ON MAGNETICS, VOL. 29, NO. 2, MARCH 1993 1683 Finite Element Simulation of Electrical Motors Fed by Current Inverters N.Sadowski, B.Carly, Y.Lefevre, M.Lajoie-Mazenc, S.Astier Laboratoire d'Electrotechnique et d'Electronique lndustrielle Unite de Recherche Associee au CNRS no 847 ENSEEIHTANPT 2, Rue Camichel 31 071 TOULOUSE FRANCE Abstract: This article presents a method of study for electric machines coupled to static converters respectively represented by a Finite Element and a circuit type model. This technique, based on a step by step process with respect to time for the simultaneous solution of the electrical circuit and electromagnetic field equations, is used for the working analysis of two permanent magnet motors fed by a load commutated current inverter. The calculation and experimental results are compared so as to validate the proposed method. I. INTRODUCTION Methods allowing the coupling of the field and electric circuit equations, have been presented and used to simulate the working of voltage inverter fed electric machines. In this case, the simulation is made by applying to the motor armature the known voltage waveshapes generated by this inverter type. The currents can be calculated by the simultaneous solution of the supply electric circuit and field equations [l]. The problem is more difficult if neither the currents in the windings nor the motor armature voltages are known. Works concerning this problem have been published over the last few years, but they remain relative to the case of generators associated with a diode rectifier bridge [2], [3], [4]. In this article, a simulation method is presented allowing the working analysis of electric machines fed by current inverters as shown in Figure 1. Current inverters are made of thyristors and the converter state is a function of the control angle of the thyristors and the machine currents and voltages. Since, neither the currents in the winding, nor the applied machine voltages, nor even the different exterior circuit configurations presented by the inverter, are a priori known, a step by step process with respect to time must be used. At each time step, the circuit configuration must be determined and the unknown currents and voltages are calculated by the simultaneous solution of the magnetic field and the corresponding electric circuit equations. 11. LOAD COMMUTATED CURRENT SUPPLY PRINCIPLE Current supply of the synchronous machine consists in imposing the current amplitude in the machine windings and its phase with respect to the electromotive force. The supply of the inverter is then ensured by a direct current source (Figure 1). This current source consists of a voltage source E connected in series with a high value inductance Lefi, to ensure a constant direct current. Rext represents the resistance associated with the Lext source inductance.
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93_FE_converotrfed - IEEE TRANSACTIONS ON MAGNETICS, VOL....

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