Alternative approach to improving efficiency level in small induction motors

Abstract

In the last few years, new requirements for induction motors efficiency have been imposed. Therefore electrical machines manufacturers have had to redefine their design criteria in order to reduce the losses level with the aim to achieve efficiency values established by the IE2 and IE3 categories of the International Electrotechnical Commission (IEC). Given that, in the near future, is expected to increase the demands regarding efficiency (IE4 and IE5 categories), it is considered appropriate to seek new alternatives to further reduce losses in induction motors. In this work the possibility of using magnetic wedges in induction motors with semi-closed slot is studied. This alternative allows a reduction on copper and core losses of the motor and thus to increase their efficiency. The study is aimed at low power motors and considers different permeability and geometries into wedges. Besides the study of losses in the machine, special emphasis is placed on the torque and starting current. Finally, an experimental validation using a 3-kW 380-V 4-pole IE2-class induction motor is presented.