Online MOSFET Condition Monitoring for Inverter-Driven Electric Machines

Abstract

Faults in electrical machines or their drives lead to degraded performance and, in some cases, unsafe operating conditions. MOSFET devices in an inverter-drive allow for higher switching frequencies. However, both power MOSFETs and Silicon Carbide MOSFETs experience degradation in the insulating gate oxide layer from excess voltage or temperature. Indicators of gate oxide degradation are measurable, but many require access to the leads of the device and additional voltage or current sensors. For an inverter-drive application, current sensors are commonly employed for controlling the machine. Detecting gate oxide degradation in the measured phase currents is noninvasive and can be performed online. In this work, degradation of gate oxide is performed in power MOSFETs and the corresponding changes in current transient waveforms are quantified.