Electric Arc Bearing Damage

Ball bearings in electric motors support and locate the rotor keep the air gap small and consistent and transfer loads from the shaft to the motor frame.

Electric arc bearing damage.

The problems isn t just the heat it is the current and the conditions in the bearing that would lead to an arc from ball or roller to the race what we are talking about is small arc strikes on the surface that become much harder than the race or bearing and as it rolls around it causes damage that then destroys the other parts. Burns created by improper electric grounding while bearing is stationary. Electric arc fluting fluting caused by electric current roller with electric arc burns adhesive wear on bearing inner ring roller flats adhesive and skidding wear on raceway surface roller end with adhesive wear cage pocket wear from excessive roller movement wear at small ends of cage pocket and on roller bridges scalloping marks in the cup. Once electric arc bearing damage has begun excessive vibrations increased heat increased noise levels and the reduced effectiveness of the lubricant will combine to shorten a bearing s service life.

But when noise occurs the damage has usually become substantial enough that failure is imminent. Either visible regular patterns flutting or. In such a case the pitting may look blackened because of oil deposits. The extent of damage to bearings depends upon the amount of energy and its duration.

Arcing can be useful but in some instances unwanted arcing causes damage to industrial structures like bearings. Improper fit damage electric current damage fluting. By some accounts electrical damage damage caused by electric discharge machining is the most common cause of failure for ac motors driven by vfds. W hen bearing fluting or other evidence of electrical damage was clear the cause was frequently believed to be due to some local condition relating to power supply grounding or to a specific vendor or product.

In extreme cases damage may occur very rapidly. This electric discharge can occur at very low voltages and may cause severe pitting of the bearing or shaft surfaces or both. There s no definitive way to predict whether or when bearing currents will occur. For instance electrical pitting may be present in the linings of bearings where there is insignificant arcing.

This has distracted many from the general and w idespread incidence of this class of bearing damage. The damage usually appears on the surface of rings and rolling elements and is similar to that produced by electric arc welding. Random electrical currents which come from multiple sources such as wiring insulation static electricity from operating equipment and so on will damage bearings.