Induction Motor Bearing Currents - Causes and Damages

Bearing damages make the biggest proportion of faults affecting AC electrical motors. There are various subdivisions of the bearing faults but one of them is the induced bearing and shaft currents in the machines. These currents cannot be fully avoided, yet with the development of power electronic control of the machines, the number of machines affected by potentially more dangerous and damaging frequency converter induced bearing and shaft currents is growing rapidly. This paper is opening the background of the nature and types of bearing currents, lists the damages inflicted by these currents and addresses problem as well as stresses the necessity of taking those currents into account for ensuring more efficient and longer lifespan of industrial electrical machines.