Paramagnetic rotor bars for three-phase squirrel cage induction machines

The concept of paramagnetic rotor bars to improve the starting performance of squirrel cage induction motors is presented in this paper. Although the induction machines are popular for their ruggedness and simplicity, their starting torque is low and the starting current is 5 to 8 times higher than the rated current. A simple solution to this problem is the introduction of new rotor-bar material with paramagnetic properties, which in turn improves the starting power factor due to enhanced skin effect. Relevant electromagnetic theory supporting this are presented in this paper. A computer simulation also produced expected results. A one horse power induction machine has been tested to verify the proposed methodology.