Novel Characterization of Si- and SiC-Based PWM Inverter Bearing Currents Using Probability Density Functions

Ryan Collin, Alex Yokochi and Annette von Jouanne
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Ryan Collin: Department of Electrical and Computer Engineering, Baylor University, Waco, TX 76798, USA
Alex Yokochi: Department of Mechanical Engineering, Baylor University, Waco, TX 76798, USA
Annette von Jouanne: Department of Electrical and Computer Engineering, Baylor University, Waco, TX 76798, USA

Energies, 2022, vol. 15, issue 9, 1-21

Abstract: The high frequency PWM voltage pulses from a two-level six-switch inverter produce a common-mode voltage in an electric machine’s windings, a fraction of which appears on the machine shaft due to electrostatic (capacitive) coupling. When the shaft voltage exceeds the dielectric strength of the bearing lubricating grease, electric discharge machining (EDM) electrostatic discharges occur within the bearing, which can lead to premature failure. According to pulsed dielectric theory, the breakdown voltage across a dielectric increases with an increase in voltage slew rate (dv/dt). Therefore, the faster voltage rise times of wide bandgap devices are expected to produce higher magnitude shaft voltages and EDM bearing currents. This paper presents circuit modeling of EDM currents and compares the shaft voltage and bearing current amplitudes of silicon- and silicon carbide-based PWM inverters through experimental measurements and a statistical analysis using probability density functions. The statistical analysis provides insights regarding the correlation between bearing failure and the number of damage causing discharges over time which is a key step in developing bearing lifetime prediction models.

Keywords: PWM; motor drive; variable frequency drive; common-mode; shaft voltage; EDM bearing current; SiC (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
References: View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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