Performances analysis of an induction motor with stator slot magnetic wedges

The medium and high power induction machines are usually built with prefabricated insulated coils. In these cases, by technological reason, the stator is designed with rectangular shape open slots. Because of the large width of the open slot, the air-gap magnetic field is distorted (comparatively with the situation of other types of slots shape), having high order space harmonics with significant amplitudes. Consequently, the pulsating torque components, noises and vibrations appear, and both the power factor and the efficiency decreases. To avoid these unfavorable effects of the open slots, the magnetic wedges are used. In this work, some aspects concerning the influence of the magnetic wedges on the performances of induction motor with open slots are analyzed. In this purpose the finite element method (FEM) and tests are used. It comes out that between the experimental results and FEM simulation results is a good concordance. This analysis confirms that the use of magnetic wedges in the case of an induction motors with open slots is a suitable solution to improve the electrical machines performances.