Using mean current vector to develop a rule base for identification of IGBT faults in induction motor drives

One of the most common fault in Pulse Width Modulation (PWM) Voltage Source Inverter (VSI) feeding an induction motor is open gate drive of the switching device (IGBT). In addition to these extreme fault cases, there may be less severe faults cases due to improper contact points, problematic solder joints, poor connections etc. Main objective of this work is to develop a rule base that not only can segregate these two different types of fault cases but also can identify the power switch in which such a fault has occurred. Rigorous simulation results using PSIM software for creating all variations of the above mentioned fault cases in a PWM VSI driven induction motor is presented for diagnosing the condition of an inverter. The 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 mean current vector is calculated. The loci of the mean current vector are plotted on the d-q plane and their patterns are observed. Shapes of these loci have been found to be effective in classifying different fault modes.