The Investigation Of Lubricate Interface Electromagnetism Damage Problem Induced By Modern Power Inverter

Modern power inverters provide the industrial control industry with significant advantages, especially the faster switching devices of pulsewidth modulated(PWM) inverters have increased drive performance. However, while the modem power inverters were used more and more widely, its disadvantages turn to be more and more serious, one of which is lubricate interface electromagnetism damage. Because the output voltage of PWM inverter is dissymmetry instantly, the common mode voltage appears as a result. The common mode voltage has high abrupt transformation rate because of the fast switching devices, whose dv/dt can exceed 6000 V/us . Under so high dv/dt, the oil film acts as a capacitor and provides a charging mechanism for rotor shaft voltage buildup. When the rotor to ground voltage is exceed the critical oil film threshold voltage, the oil film breakdown induce a large current, and even appear electric discharge machining (EDM) current. Therefore, the lubricate interface is damaged. This damage was often occurred in the surface of bearing or gear that connected with motor shaft, induce the bearing or gear premature.This paper mainly study electromagnetism damage problem on the bearing lubricate interface induced by modern power inverter. Investigate the different forms of rotor to ground voltage and bearing currents. Examines the mechanism and electrical characteristics of bearing, and converts them into common mode voltage models in PWM inverter control system. Abstract and analysis the signal of rotor to ground voltage via experiment. Compare the result of simulation and signal abstracted from experiment in order to show the correctness of model. Study the factors which can influence the rotor to ground voltage and bearing currents. Give a ways to estimate the electrical life of a mechanical bearing by building the relationship between the current density and bearing life. Establish the quantificational method to measure the magnitude of lubricate interface electromagnetism damage. Search the possible techniques to eliminate or mitigate lubricate interface electromagnetism damage problem.