Change of stray loss of a cage induction motor with axial variation of the interbar resistance

It has been suggested that the solution of the relevant nonlinear differential equation would show that decreasing the interbar resistance at the central coreplates of the rotor of a cage induction motor results in a decrease of the interbar-current loss, with a consequent decrease of the stray loss. It is demonstrated here that such a conclusion is not necessarily true. Under certain circumstances, a decrease of the interbar resistance at the central coreplate can result in an increase of the stray loss. In particular, a specific linear change of the interbar resistance from each corestack end to its centre is assumed, and a plot obtained of the interbar loss with varying mean interbar resistance. Surprisingly, when other linear changes are considered, the maximum loss remains the same, but occurs at different values of the mean interbar resistance. A discussion is given of the practical implications.