Detection of Early Inter-Turn Stator Faults in Induction Motors via Symmetrical Components - Current vs Stray Flux Analysis

Early inter-turn short circuits are among the most challenging faults to detect in electrical machines. It is not only difficult to identify the fault, but the diagnosis and decision-making time are crucial since the severity of this fault increases very fast, leading to a catastrophic breakdown. The monitoring of the symmetrical current components is a method that has received a lot of attention among other popular methods. However, it has been lately shown that classical methods may be insensitive to early faults leading to false positive diagnostic conclusions. The symmetrical components of the current has been one of the most trustworthy method. However, it is shown in the paper that even this method may lead to a false conclusion. The authors suggest for the first time, the symmetrical components of the stray flux as a reliable method to detect early inter-turn faults in induction motors. The work is supported by finite element analysis and experimental testing.