Motor End Plates

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The end plates house the bearings for the motor. The end plate and bearing call be seen in the picture of the rotor that is shown in Fig. 1b. If the motor is a fractional-horsepower motor, it will generally use sleeve-type bearings and if the motor is one of the larger types, it will use ball bearings. Some ball bearings on smaller motors will be permanently lubricated, while the larger motor bearings will require periodic lubrication. All sleeve bearings will require a few drops of lubricating oil periodically.

The end plates are mounted on the ends of the motor and held in place by long bolts inserted through the stator frame. When nuts are placed on the bolts and tightened, the end plates will be secured in place. If the motor is an open type, the end plates will have louvers to allow cooling air to circulate through the motor. An access plate may also be provided in the rear end plate to allow field wiring if one is not provided in the stator frame.

If the motor is not permanently lubricated, the end plate will provide an oiler tube or grease fitting for lubrication. It's important that the end plates are mounted on the motor so that the oiler tube or grease fitting is above the shaft so that gravity will allow lubrication to reach the shaft. If the end plate is rotated so that the lubrication point is mounted below the shaft, gravity will pull all of the lubrication away from the shaft and the bearings will wear out prematurely. If one needs to remove the end plates for any reason, they should be marked so that they will be replaced in the exact position from which where they were removed. This also helps to align the holes in the end plate with the holes in the stator so that the end Plates can be reassembled easily.

Rotor Operation of an AC Induction Motor Home