Influence of bearing currents on the bearing lifetime for converter driven machines

The possibility to calculate motor bearing currents from motor geometry and the mechanisms that lead to these currents are known today [1], [2]. The precise mechanical and electrical procedures which lead to the well known corrugated patterns, a "mountain/valley" structure in the bearing raceway, which reduces the bearing lifetime, are still unknown. But, this paper will present research results that can clarify, which operating conditions will lead to these corrugated patterns. As a result, one can estimate the endangerment of a drive system with a wide speed range and different temperatures.