Rotor Design Optimization of Squirrel Cage Induction Motor-Part II: Results Discussion

The rotor slot geometry of a squirrel cage induction motor plays the most important role in defining the torque-speed characteristic when the power supply is directly provided by the main grid. In this article it is shown how the rotor slot geometry can be optimised to satisfy different electromechanical requirements, depending on specific applications. This work, the second of two companion papers, briefly recalls the novel systematic approach, proposed in Part I, to perform the optimization of squirrel cage induction motors. Here, the optimization results achieved satisfying a wide spectrum of requirements are analysed in depth. Furthermore, the trade-off among the several performance indexes, and their correlation with the geometrical parameters is discussed. The possible advantages, and disadvantages of adopting a copper cage is also quantified for all possible performance requirements. The influence of the motor thermal behaviour, and harmonic losses on the overall performance are also discussed allowing to validate the proposed design optimization procedure, and its results. The outcomes of this work are opening to new design approaches that enable to optimise the performance of one of the most popular electrical machines adopted in industry, the squirrel cage induction motor.