Experimental inter-turn short circuit fault characterization of wound rotor induction machines

The aim of this paper is to compare different experimental techniques for detecting a stator inter-turn short-circuit in a Wound rotor induction machine working as generator. Three methods using different signals such as stator or rotor current and the leakage flux will be described and experimented. The rotor currents provide interesting signatures since the stator faults introduce new harmonics in the rotor windings. Hence, in this paper, it is proved that sensing one rotor current by using a current sensor is one of possible techniques for detecting this kind of electrical fault. The leakage flux is another alternative for this kind of problems since in this paper; it is proved that a simple external leakage flux sensor is efficient to detect, in the low frequency range, the intern-turn short circuit in three-phase induction machines even in presence of power supply harmonics. Stator currents space vector is also an interesting technique since it is proved that inter-turn short circuit faults can be considered as a stator unbalance which can be detected using negative sequence of stator currents. The comparison of these three methods is performed using experiments on a 5.5kW-220V/380V-50Hz-8 poles wound-rotor induction machine working in both healthy and faulty modes at different load conditions.