Ahtrucf-Realising control of standard induction machines at low and zero speed without mechanical sensor implies the use of parasitic non-fundamental wave effects. Different schemes have been proposed in the past which exploit the inherent saliencies of saturation andlor rotor slotting to detect the main flux and the rotor position. They all use a high frequency or transient signal in addition to the fundamental wave excitation which is impressed by the inverter. The machines reaction on this high frequency excitation is measured and the flux andlor rotor position signal is extracted by special algorithms.However, this transient electrical behaviour and the resulting control signals of an induction machine are strongly influenced by the design of the machine and especially the shape of the lamination.The two most prominent saliencies, present in standard induction machines are caused by saturation and slotting, enabling thus either sensorless flux or rotor position detection.Especially the rotor position detection suffers from a strong dependence on the slot geometry of the lamination. Yet the details for this influence are not quite clear and have not been addressed in Literature. In this paper measurements were performed on machines giving a comparison of closed and opened rotor slots. With the help of measurement windings placed along the air gap the spatial distribution of the transient leakage flux caused by the high frequency excitation is determined to make an interpretation of the transient behaviour more accurate.The measurements made in this paper are based on a transient excitation of the machine with voltage pulses. The results are however also applicable to high frequency sinusoidal excitations.
A model is presented in this work which is capable to calculate the magnetic behavior and iron losses of a ferromagnetic lamination in a wide frequency range. It is based on an energetic hysteresis model and extends its static approach with eddy-currents in a finite-difference simulation of a lamination sheet. This will also consider the field displacement or skin-effect which cannot be ignored in the lamination sheets of electric machines especially if they are supplied from fast switching power converters. As there is no restriction with respect to the time-dependence of the exciting voltage, the presented approach can be used in machine models to predict the losses for such power converter operation and its pulse-width modulated voltages.
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