The effect of induction motor design on losses and efficiency for adjustable-frequency drives

The dependence of losses and efficiency on design characteristics of a squirrel cage induction motor fed by a voltage source inverter, is analysed in this paper. A model based on harmonic equivalent circuits is used to study the influence of circuital parameters and motor geometry on the magnitude of losses. An analysis of parameter sensibility shows that a motor with large leakage inductance presents an important reduction of losses and an insignificant reduction of fundamental torque. Thus, it is found that motors with a small number of stator and rotor slots, deep slots and large diameter/axial length ratio, present low losses and high efficiency