Motors are devices that convert electrical energy into mechanical energy. It's windings and magnets are situated around and on central shift, which is usually supported by various rolling-element bearings. These bearings are the lubricationpoints, that usually are virtually lubricated with grease. However, in some cases, small- and fractional-horsepower motors use bolted bearings, without making any lubrication supply to external bearings. Motor lubrication, if balanced, not overloaded, and aligned, has long life.
On the other hand, if big motors that are, at times, subjected to more load, requires larger bearings and better lubrication. External grease fittings are set up on motors looking at their design and manufacture. As motors become more heavy and powerful, the bearings point require grease replenishment at much more frequency than the light motors.
If a motor is being operated at high efficacy, the space between cage, seals, balls and raceway require to be filled with 30 to 50 percent capacity of motor lubrication. The reason for that is the bearings are installed behind end plates, and they are more likely to be overfilled, specifically in the case of manual greasing. If it happens, the windings lead to premature failure, which reduces the efficiency ofmotor. To avoid such situations, heavy motors are manufactured with a screw or drain-plug, which when opened allows excess lubricators to flow via bearings, thus completing the motor lubrication process effectively. So, don't keep it close while lubricating the motors as excessive grease can find its way into the winding, hence damaging your motors.
However, nowadays, there are various equipment available that uses single-point auto lube setup like Grease-guns. They uses a small amount of grease on a frequent basis for motor lubrication, depending on the size of the motors.