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 that 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.

Type of bearings are used in electric motors

Bearings are a critical component in electric motors, as they enable the smooth and efficient rotation of the shaft within the motor. The choice of bearing type in an electric motor depends on the specific motor design, load conditions, operating environment, and other factors. Electric motor engineers carefully consider these factors to select the appropriate bearing type that ensures optimal performance, longevity, and efficiency for the given application.

Thrust Bearings: Thrust bearings are designed to accommodate axial (thrust) loads, allowing components like motor shafts to withstand forces along their axis. These are crucial in electric motors where there are axial loads, especially in high-speed and heavy-duty applications.

Usage: Thrust bearings are employed in electric motors that experience significant axial loads, as seen in applications like automotive transmissions.

Tapered Roller Bearings: Tapered roller bearings are capable of handling both radial and axial loads. They are often used in electric motor applications where there is a combination of heavy radial and thrust loads, such as in automotive wheel hubs or industrial gearboxes.
Usage: Tapered roller bearings are found in electric motors that handle combined radial and axial loads, like those used in industrial gearboxes.

Single Row Radial Ball Bearings: These are one of the most common types of bearings used in electric motors. They consist of an inner and outer ring with a set of steel balls in between. Single row radial ball bearings are designed to handle radial loads, which are forces acting perpendicular to the motor’s shaft. They are suitable for applications where the load primarily comes from the weight of the motor components and any external forces acting perpendicular to the shaft.
Usage: These bearings are commonly used in electric motors for small appliances, fans, and other low to moderately loaded applications. They support the motor’s rotor and enable it to rotate smoothly.

Deep Groove Ball Bearings: Deep groove ball bearings are a subtype of radial ball bearings designed for applications with high-speed requirements. They have a more extensive contact area between the balls and raceways, making them suitable for electric motors operating at high speeds, such as those found in small appliances and fans.

Angular Contact Ball Bearings: Electric motors often require bearings that can handle both radial and axial loads simultaneously. Angular contact ball bearings are designed for this purpose. They have raceways that allow them to accommodate both types of loads and are commonly used in applications where the motor’s shaft experiences axial as well as radial forces. This is particularly useful in applications such as thrust loads or when precise positioning is required.
Usage: Electric motors requiring both radial and axial load support, like those found in machine tools and robotics, often utilize angular contact ball bearings.

Self-Aligning Ball Bearings: Self-aligning ball bearings can accommodate misalignment between the shaft and housing, making them suitable for electric motors that may experience shaft misalignment due to assembly variations or operational conditions. They help reduce friction and wear caused by misalignment.

Spherical Roller Bearings: Spherical roller bearings are designed to handle heavy radial and axial loads and are commonly used in electric motors for large industrial applications where there may be significant misalignment or heavy loads, such as in conveyors and crushers.

Needle Roller Bearings: Needle roller bearings are characterized by their cylindrical rollers with a high length-to-diameter ratio. They are used in compact electric motor designs and applications where space is limited and high radial load capacity is required, such as in small appliances, power tools, and automotive starter motors.

Deep Groove Ball Bearings, Self-Aligning Ball Bearings, Spherical Roller Bearings, and Needle Roller Bearings bearing types serve specific purposes within electric motors, such as accommodating high-speed rotation, misalignment, heavy loads, and space constraints, depending on the motor’s design and application.

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. Go to [email protected] or visit www.pibsales.com