New Harmonics for Early Detection of Inter-Turn Faults in Induction Motors During Start-Up

Stator inter-turn faults (ITFs) are one of the most challenging to detect: in their early stage they are too subtle, and on the other hand they rapidly evolve into a catastrophic failure. In turn, its detection is of prime importance, since it is one of the main reasons for motor failures in medium and high-voltage induction motors (IMs). This paper discovers and fully characterizes a family of new ITFs-related harmonics not described before in previous literature. For that purpose, a deep finite element analysis of three motors with different characteristics is conducted, under different fault stages. The appearance mechanism of these new harmonics is physically described, the formula for their time-frequency trajectories is derived and the flux sensor design is optimized for their detection. Finally, the existence of these harmonics is proven in a 0.75 kW IM through a novel methodology that emulates the electromagnetic effects of an ITF but without endangering the stator's windings.