Validation of sequence circuits useful for split-phase current signature analysis (SPCSA) and diagnosis of eccentric-rotor traction cage motors

A squirrel-cage three-phase induction motor with eccentric rotor and parallel connections in the stator can be represented by five equivalent sequence-circuits of virtually centered-rotor machines, as mathematically proved in a companion paper. The five circuits allow the calculation of stator and rotor fault-related currents, in form of 2(p±1)-pole space vectors for 2p-pole machines. The formal calculation of fault-related currents is very useful for defining fault indicators and tools for diagnosis, and in case of parallel-connected stators (like in many traction motors) the split-phase current signature analysis becomes possible. This paper validates the sequence-circuit modeling by comparing the theoretical results with simulations of a 1130kW traction induction motor with static, dynamic, and mixed faults in both no-load and full-load conditions. The simulations are carried out by using a full mesh-model of the motor, implemented by winding functions. A good match is obtained between theoretical calculations and simulations. Moreover, the role of the cage damping on the eccentricity-related current signatures is evidenced. It is shown that the cage damps not only the signature of static fault but also that of dynamic fault, and that the damping itself is load-dependent in the latter case.