A new research for the symptoms and diagnosis schemes of the inner-faults for three-phase induction motors

Based on the references [Linzheng Zhang et al], this paper focuses on the early detection of the winding faults in the induction motors and their possible fault symptoms, to avoid catastrophic failure, and to reduce repair cost and outage time to a minimum. The fault symptoms of stator winding inter-turn short circuit and rotor bar breakage are analyzed deeply and completely. For the stator winding inter-turn short circuits, various symptoms namely the changes on the ratio of the stator negative phase sequence current to the stator negative phase sequence voltage with the on-line consideration of fundamental frequency f₁ and slip s, are considered. Among those symptoms, when the rotor bar is broken, there is another additional component, which is (1+2s)f₁. A clear proof from the theorems of electrical motors for the component of (1+2s)f₁ is presented. This paper proposes new detection schemes based on the various symptoms for rotor bar breakage and stator winding interturn short circuit faults in the squirrel cage induction motors, in order to avoid the mis-diagnosis and increase its reliability.