Efficiency optimization in small induction motors using magnetic slot wedges

•Changes in the world use of energy resources have given rise to a new challenge for the design of electric machines.•The IEC has proposed new regulations with growing efficiency levels on squirrel-cage induction motors.•Electrical machines manufacturers have had to redefine the design criteria in order to achieve the efficiency values established by the IEC.•The introduction of magnetic wedges allows increase the semi-closed slot induction motors efficiency. In the last few years, new efficiency requirements for induction motors have been imposed. Therefore electrical machines manufacturers have had to redefine the design criteria in order to reduce losses aiming to achieve the efficiency values established by the IE2 and IE3 standard categories according to the IEC. Given that, in the near future, an increasing demand regarding efficiency (IE4 and IE5 categories) is expected, it would be appropriate to seek new alternatives to further reduce losses in induction motors. In this work, the possibility to use magnetic wedges in induction motors with semi-closed slots is studied. This strategy allows to reduce copper and core losses, therefore increasing then the motor efficiency. The study analyses low power motors and considers different permeabilities and geometries for the magnetic wedges. In addition, it focuses attention on the starting torque and currents. Finally, an experimental validation using a 3-kW 380-V 4-pole IE2-class induction motor is presented.