What is Electrical Discharge Machining (EDM)?
EDM or fluting, as it is more commonly referred to, is the passage of electrical current through the bearing. This fault is also referred to as frosting, electrical pitting, and electric arc damage. Even though this paper focuses on bearing damage resulting from fluting, please note gears, couplings, seals, etc. can also be damaged. The following two conditions must exist for current to flow: 1) there must a voltage potential and 2) there must be a path to ground. Current takes the path with the least resistance and in most cases this is through the motor bearings. However, it also is possible for the path to be through the bearings of a connected component such as a gearbox or a tachometer (see Figures 1, 2, 3 and 4). On motors with a tachometer directly connected, the tachometer bearings typically are damaged first since the smaller bearings offer the path of least resistance to ground [3]. The bearing’s lubrication plays an important role in determining the path of current flow. The
