Rolling Element Bearings In Electric Motors

More v

Rolling-element bearings in electric motors support and locate the rotor, maintain a small and consistent air gap between the rotor and stator, and transfer loads from the shaft to the motor frame. The correct bearings for an application let a motor run efficiently across its design speed range, minimize friction and power loss, produce little noise, and have a long service life.On the other hand, bearings can be quickly ruined when a motor is used improperly. For example, the deep-groove ball bearings optimized for in-line couplers can overload if motors fitted with them drive a belt pulley. Likewise, motors containing roller bearings for heavy belt loads may prematurely fail when run with an in-line coupler because a minimum load is not maintained.Electric motors typically incorporate a locating and nonlocating bearing arrangement to support the rotor and locate it relative to the stator. Locating bearings position the shaft and support radial and axial loads, while nonlocating bearings handle radial loads and let shafts move axially to prevent overloading from thermal expansion.The most common setup for smaller motors in horizontal machines consists of a pair of deep-groove ball bearings mounted on a short shaft in a cross-locating arrangement. Medium and large electric motors typically use deep-groove ball bearings for locating. The nonlocating bearing may be a ball bearing, cylindrical-roller bearing, or toroidal-roller bearing, depending on the loads, speeds, and operating environment. Motors for vertical machines typically incorporate deep-groove ball bearings, angular-contact ball bearings, or spherical-roller thrust bearings.LOADS AND SPEEDSRegardless of type, bearings need a minimum load so rolling elements rotate and form a lubricant film rather than skid. Skidding raises operating temperatures and degrades lubricants. A general rule of thumb for roller bearings places a minimum load equal to about 0.02 times the dynamic radial-load rating. For ball bearings, that number is 0.01. Maintaining (at least) minimum loads is especially important when bearings see high accelerations and speeds that are roughly 75% of recommended ratings.In general, power output governs shaft size and bearing bore diameter. Of course, load magnitude and direction also determines bearing size and type. Designers sizing motor bearings should consider additional forces such as magnetic pull from unsymmetrical air gaps, out-of-balance forces, pitch errors in gears, and thrust loads.The calculation of loads on a single bearing models the bearing shaft as a beam resting on rigid, moment-free supports. Assuming the resulting load is constant in magnitude and direction, the equivalent dynamic bearing load comes from the general ABMA and ISO equation:

Best services for writing your paper according to Trustpilot

Premium Partner
From $18.00 per page
4,8 / 5
4,80
Writers Experience
4,80
Delivery
4,90
Support
4,70
Price
Recommended Service
From $13.90 per page
4,6 / 5
4,70
Writers Experience
4,70
Delivery
4,60
Support
4,60
Price
From $20.00 per page
4,5 / 5
4,80
Writers Experience
4,50
Delivery
4,40
Support
4,10
Price
* All Partners were chosen among 50+ writing services by our Customer Satisfaction Team
You Might Also Like