Types of Bearings Used in Electric Motor

Electric Motor Bearings, also known as EMQ bearings, are manufactured for electric motors. However, many manufacturers have created an EMQ standard which applies to all bearings they manufacture. For example, JEM bearings manufactured by SKF are manufactured with J steel retainers and designated as “EM” for electric motor quality. Electric motor quality means each manufacturer has a noise specification, usually a C-3 internal clearance and grease specified for use in electric motors. SKF has a noise specification designation of QE6 and denotes GJN as specifying high quality polyurea-thickened grease Mobil Polyrex EM.

Whenever a bearing is designated EMQ or EM it indicates the manufacturer is stating that the bearing is manufactured meeting certain standards for use in electric motors. Unlike other bearing standards such as AFBMA, ABEC, and others, EMQ is not a universal standard. Bearing manufacturers like NTN, SKF, TPI, and FAG may all have EMQ bearings but each of them may have a different type of grease, radial play, and slightly different noise specifications.

Single Row Radial Ball Bearings

Single Row Radial Ball Bearings are used in general purpose motors, severe duty motors, explosion proof motors, farm duty motors, and pump motors to name a few. As with many applications, numerous factors determine the final bearing design. As a rule of thumb, if a bearing is used in an electric motor application you can start by selecting an EMQ bearing and then go from there. Environment, ambient temperatures, loads and speeds, starting and stopping, and other factors may change some of the specifications to come to the best solution for bearing’s final specifications.

Cylindrical Roller Bearings

Cylindrical Roller Bearings are ideally used in electric motors especially for applications where thermal expansion of the main shaft is possible. Due to the rings being free to move in the axial direction and having a high load capacity, the cylindrical roller bearing is often used in larger electric motors.

Insulated Ball Bearings

Insulated Ball Bearings are a helpful solution for electrical pitting for electrical power generators and motors. As a result of electrical leakage, an electrical current can pass through a bearing where the current arcs between the rolling surface and the rolling elements. The arc will heat up the temperature of the steel, changing its structure. The changes caused by the arcing will cause the bearing to ultimately fail. Electrical pitting of bearings can be prevented using ceramic hybrid bearings or a coated bearing.

Many manufactures such as FAG, SKF, and NTN offer insulated bearings that have been designed to specifically combat electrical pitting known as Coated Bearings. The coating is a resin applied to the outer ring of the bearing, providing a barrier. The coating can resist a minimum of 100 Mega ohms and up to 2000 Mega ohms at 500VDC. This prevents currents from passing through the bearing thus extending its life.

Resin coated bearings are often used on Wind Turbine generators, traction motors, variable speed motors, and motors used in wastewater treatment facilities. Any application where potential stray electrical current is present should use coated bearings.

Ceramic hybrid bearings

Ceramic Hybrid bearings are steel rings and ceramic balls thus termed “Hybrid.” The use of silicon nitride rolling elements provides excellent electrical insulation and improves heat dissipation. The use of hybrid bearings means no lubrication, less rotating mass, less maintenance, and longer life. Applications for ceramic hybrid bearings include generator motors used in wind energy, reducing difficult to access maintenance.

With more than 40 years of expertise in ball bearings, Pacific International Bearing offers one of the industry’s widest array of products to meet your requirements. Our offering of ball bearing manufacturers includes SKF, NTN, TPI, FAG, NMB, IKO, and Kaydon and are available as off-the-shelf. PIB offers sizes ranging from 10 mm to 320 mm outside diameters. With a large inventory and access to worldwide stock, there is no reason to go anywhere else for your ball bearing needs.

Please contact PIB for further information.