Grease in Electric Motors

Grease is the most widely used lubricant in electric motors.  Grease is used in motors with ball and roller bearings. 
The function of grease is
  • to minimize friction and wear
  • To prevent corrosion and
  • to prevent the entry of foreign objects which can contaminate the bearing.

Grease, thus, has a sealing effect.  Grease is a semi-solid lubricant.  It is composed of a base oil, additives and a thickener.  The base oil can be synthetic or natural.  Synthetic oils are used in applications with high temperatures and longer regreasing intervals. 

The function of the thickener is to prevent the base oil from leaking.  Thickeners are usually metallic soaps.  Additives include oxidation and corrosion inhibitors, anti-wear agents.

The grease in motors will have to be replaced over time.  The regreasing intervals are based on the bearing manufacturers' recommendations.