ANALYSIS OF FIELD-WEAKENING POSSIBILITIES OF PERMANENT-MAGNET SYNCHRONOUS MOTORS

In this paper, we study the extending of speed range of motors (or generators) with permanent magnet inductor and supplied by electronic converter. The amplitude of phase voltage and current waveforms are limited by electronic supply. The aim of this study is to achieve a maximum power near of the base speed one on an extended speed range. This require an airgap flux weakening so called ''flux-weakening'' above base speed. A parametric analysis of motor electromagnetic characteristics is made to show the influence of armature reaction and magnetic saliency on speed range. We show that exists an ideal condition to obtain a constant power speed range theoretically unlimited. Magnetic saliency permits to enhance the power factor especially when L(d) > L(q). AS main hypotheses, we consider no saturation, e.m.f. and current sine waveforms and a sinusoidal airgap flux density. Finally, we recapitulate the permanent magnet rotor structures able to obtain a flux-weakening operation.