Calculation of starting torque in skewed-rotor cage induction motor with broken bar and rotor eccentricity using hybrid analytical/finite element analysis technique

This paper addresses the variation of starting torque in a 3-phase induction motor. It presents some example results from an experimental investigation then develops a hybrid analytical/finite element method for rapid assessment of the starting torque variation with rotor position. The method allows for rotor skew, broken bars and rotor eccentricity. Simulations are put forward to illustrate the method which is shown to be effective in modeling the parasitic effects due to MMF variations and asymmetries. It demonstrates that if a bar is broken at one end of a skewed rotor, then the starting torque characteristics will be different in opposite rotational directions. This is validated with experiments.