Application of wavelet transform to identify faulty IGBTs in 3-phase induction motor drives

Switching Devices (IGBT) used in Pulse Width Modulation (PWM) Voltage Source Inverter (VSI) feeding an induction motor often suffers from different types of faults due to ageing or performance in unfriendly environments. These faults which are caused due to improper contact points, problematic solder joints, poor connections etc are often less severe at their initial stages. Different variations of the above mentioned faulty cases in a PWM VSI driven induction motor are simulated in PSIM software and results are diagnosed to estimate condition of the inverter. Three phase line currents feeding the motor are recorded and transformed to d-q reference frame using Park´s Transformation for further analysis. From d and q current components thus obtained, the PVMs and PVACs are computed. Applying Continuous wavelet Transform on PVACs certain features are extracted which are helpful to distinguish healthy condition from faulty situations and segregates different cases of individual faulty IGBTs.