What types of bearings are most frequently used in motors?
2015-11-16Anti-friction / rolling element bearings are most frequently used. These bearings are characterized by rolling elements which separate the stationary part from the rotating part. Specific types of these bearings include:
- Deep Groove Ball Bearings
- Double Row Angular Ball Bearings
- Cylindrical Roller Bearings
- Spherical Roller Radial Bearings
- Angular Contact Ball Bearings
- Spherical Roller Thrust Bearings
Following is a brief description of each bearing type listed:
Typical bearing manufacturing series numbers used range from 6200 to 6400.
Deep groove ball bearings are available in open type bearings, shielded bearings (single or double), and sealed bearings. Open type conrad bearings, which are supplied on explosion proof 180 frames and higher and ODP/TEFC 400 frames and higher, require bearing caps to contain grease in the housing. Shielded bearings, supplied on all 140 frames (ODP/TEFC through 360 frame and on all automotive duty), can be used on motors without bearing caps. Sealed bearings, which are “lubed for life”, possess a reduced speed limit due to seal friction. These sealed bearings are supplied for customer specials only.
Double Row Angular Ball Bearings
Deep groove ball bearings are the most common type of bearing for electrical motor use. These bearings are good for moderate radial and axial loads. They are used in vertical high thrust motors as a guide bearing for momentary upthrust.
Typical bearing manufacturing series numbers used range from 5200 to 5400.
Double row angular ball bearings are very similar to single row conrad bearings, with the addition of an extra row of balls. Because of this addition, these double row bearings can handle larger radial and axial loads than conrad bearings. Double row angular ball bearings, available open, shielded, or sealed, are provided on both horizontal and vertical close-coupled pumps, and on larger normal thrust motors as thrust bearings. Sizes larger than 5316 are not readily available.
Typical bearing manufacturing series numbers used are preceded by an “N”. For example: N2XX or NU2XX.
Cylindrical roller bearings are used on horizontal motors where high radial loads are present. Although equivalent in size to conrad ball bearings, cylindrical bearings have a lower speed limit and are only available as open type bearings. These bearings are not available for direct connected motors, and are provided upon special order only on motors with an overhung load.
Spherical Roller Radial Bearings
Typical bearing manufacturing series numbers used range from 22,000 to 24,500.
Spherical roller radial bearings are used on horizontal motors which possess an extremely high radial load, or on motors which require an extended bearing life. Typically, these bearings are wider than conrad ball bearings, thus. making special engineering more difficult. In addition, they have a lower speed limit than cylindrical roller bearings. Spherical roller radial bearings can not withstand axial loading.
Angular Contact Ball Bearings
Typical bearing manufacturing series numbers used range from 7200 to 7400.
Angular contact ball bearings are supplied on vertical motors only. High thrust vertical motors using single angular contact bearings are capable of continuous thrust in only one direction. Multiple angular contact ball bearings can be mounted either back-to-back for up/down thrust, or in tandem sets of two or more bearings for extra high thrust loading.
Spherical Roller Thrust Bearings
Typical bearing manufacturing series numbers used range from 29,300 to 29,400.
Spherical roller thrust bearings are supplied on vertical motors only. These bearings can support extremely high thrust loads (up to 300% of standard thrust capacity) and moderate radial loads. Preload springs are required to supply minimum downthrust to bearings at start up in order to prevent bearing skidding. In addition, the motor requires minimum downthrust at all times to compress preload springs and unload the lower guide bearing for maximum life. Water cooling is generally required.
