Nishad Patila , Diganta Dasa and Michael Pechta,b
aCALCE, University of Maryland, College Park, USA.
bCity University of Hong Kong, HK.
Insulated gate bipolar transistors (IGBT) are used in critical application areas such as inverters in hybrid cars, motion control systems for variable speed motor drives and high power switch mode power supplies. In these critical applications, diagnostic approaches are required to monitor the health and predict the reliability of these devices to prevent system downtime and costly failures. In this study, Mahalanobis distance (MD) was used for anomaly detection for non punch through (NPT) IGBTs. The IGBTs were aged by electrical-thermal stress under a resistive load until their failure. Monitored collector-emitter voltage and collector-emitter currents were used as input parameters to calculate the Mahalanobis distance (MD). The MD values obtained from the healthy data were transformed using a Box-Cox transform and three sigma limits were obtained from the transformed data. The upper three sigma limit of the transformed MD healthy data was used as a threshold to detect degradation in the IGBTs. The MD anomaly detection approach allowed for detection time of anomalies in NPT IGBTs up to 77% before failure.
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