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T. Wolbank, R. Wöhrnschimmel, M. Diakite, B. Haidvogl, H. Hauser:
"A Model to determine the transient behaviour of ferromagnetic materials in inverter-fed electrical machines";
Poster: Int. Conference on Electrical Machines (ICEM 2000), Espoo Finland; 28.08.2000 - 30.08.2000; in: "International Conference on Electrical Machines", (2000), ISBN: 951-22-5097-7; S. 1666 - 1670.

For the design of electrical machines and for the realisation of control schemes of electrical drives it is usually sufficient to know the steady state or low frequency magnetical behaviour of the material used. However, if the goal is to determine local differences of the leakage inductances of the machine in order to estimate the flux or the rotor position without mechanical sensor, it is necessary to take into account also the transient characteristics of the magnetic material.
One sensorless control method of electrical ac drives is the INFORM method ("Indirect Flux detection by On-line Reactance Measurement") [5]. It detects the local differences by evaluating the change of the stator current space phasor due to stator voltage test phasors. This change however is not only influenced by the position of the rotor reference to the stator and by the low frequency magnetic behaviour of the lamination. Thus it is necessary to take into account also dynamic processes in the material. To achieve this, a model has been developed to simulate the magnetisation process in an induction motor fed by a voltage source inverter.
The proposed model calculates the current change due to voltage pulses taking into account the hysteresis as well as eddy currents. In order to limit the time, necessary to carry out a calculation of a whole machine the model has to be kept simple.
In addition measurements on an inverter fed induction machine as well as on a stator lamination are presented to verify the applicability of the model.