Development of a Test Rig for Fault Studies on a scaled-down DFIG

In this work, an experimental test rig has been set up based on a 5kW wound rotor induction machine (WRIM) that was developed and built in the university laboratory as a scaled-down version of a typical 2.5MW doubly fed induction generator (DFIG), with the main aim of conducting various fault studies on the developed micromachine. To achieve this, the scaled-down machine has been customized by modifying the stator and rotor windings such that various inter-turn winding fault conditions may be achieved at different severities. Moreover, the micromachine has also been modified to make it possible to implement a static eccentricity fault. The dimensional analysis & scaling methodology that was used to scale down the large scale DFIG into the micromachine has been briefly discussed in this paper. To evaluate the performance of the developed test rig, experiments have been carried out by separately implementing the stator and rotor inter-turn short circuit faults (ITSCFs) as well as the static eccentricity (SE) fault on the micromachine and capturing the real-time stator current signals for further analysis in MATLAB, in an attempt to diagnose the presence of these faults using the conventional motor current signature analysis (MCSA). The results obtained from the stator current spectral analysis have demonstrated that the presence of a stator ITSCF, rotor ITSCF and SE fault in the micromachine gave rise to additional frequency harmonic components in the stator current spectrum. Moreover, it was observed that the magnitudes of the fault-related frequency components increased as the interturn winding fault severity was increased. Therefore, the developed test rig can be successfully used for further fault studies and ultimately develop advanced and novel fault diagnosis techniques.