Calculation of motor capacitances for prediction of discharge bearing currents in machines of inverter-based drive systems

Abstract

The occurrence of high frequency discharge bearing currents (also: "EDM-currents") that can occur in machines of inverter-based drives systems depends strongly on the value of the capacitive voltage divider BVR (Bearing Voltage Ratio) of the machine. This paper presents a straightforward approach to calculate the involved motor capacitances in order to predict the occurrence of discharge bearing currents in inverter-based drive system. The approach is based on the design parameters of the machine and does not involve additional measurements. It combines ease of application and satisfying accurateness and allows prediction of the risk of endangerment of an inverterbased drive system due to discharge bearing currents. Index Terms-bearings (mechanical), failure analysis, variable speed drives0-7803-8987-5/05/$20.00 ©2005 IEEE.264

Scaling Effects of Inverter-Induced Bearing Currents in AC Machines

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