Investigation of Bearing Current and Degradation in Wide Bandgap Inverter Fed Electric Machines

Wide bandgap (WBG) power devices can operate at higher switching speed, resulting in lower power losses compared to silicon power devices. However, the fast-switching speed and high switching frequency leads to the bearing degradation in WBG motor drives. This paper investigates the impact of bearing voltage waveform such as the frequency and amplitude on bearing currents and bearing damage. The accumulated Electrical Discharge Machining (EDM) current inside the bearing is experimentally measured to study the impact of different operating conditions and correlate it with actual bearing damage. A comprehensive analysis of testing time and electrical parameters is conducted to gain deeper insights into the principles of bearing current and bearing degradation. The results show that the amplitude of the bearing voltage is a key factor influencing the occurrence rate and peak value of EDM current and is a critical factor in bearing raceway damage.