Steady-state analysis of double-cage induction motors with rotor-cage faults

An analysis is developed for a double-cage induction motor with any number of cage or end-ring faults. Both common end-ring and separate end-ring designs are considered. The paper addresses, in particular, the problem of detecting faults in the outer cage when the machine is running, and identifies the response of the machine to negative sequence voltages as a possible means of doing this. Experimental results are presented for a 15 kW test motor.