THE EFFECTS OF PWM VOLTAGE-SOURCE INVERTERS ON THE MECHANICAL PERFORMANCE OF ROLLING BEARINGS

Modern power inverters provide the industrial control industry with si gnificant advantages. The faster switching devices have increased driv e performance, but with some recently discovered disadvantages, One di sadvantage, rotor shaft voltage and resulting bearing current, has bec ome an industry concern, The oil film in a bearing acts as a capacitor and provides a charging mechanism for rotor shaft voltage buildup, El ectrical breakdown of the film can damage the bearing, This paper exam ines the mechanical and electrical characteristics of the bearing and converts them into models, The mechanical model for the bearing contac t area establishes an allowable bearing current density, which is used to estimate the electrical life of a mechanical bearing, The electric al model for the bearing provides a significant advancement, aids bear ing design, and the analysis of electrically induced bearing damage, F inally, the paper presents quantitative results for one solution to th e shaft voltage and bearing current problem.