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Large Industrial Electric Motor Specialists

Different Types of Electric Motor Bearings

Table of Contents

When selecting a bearing for a large industrial motor, you’ll need to consider several factors to ensure you choose the right product for your application. The bearing type impacts performance, maintenance needs, and longevity of your motor. This guide covers the major classes of bearings to help simplify the selection process.

Rolling Element Bearings

Rolling element bearings, or roller bearings, use small spherical elements like balls or rollers between inner and outer races. They excel in applications with high speeds or light loads.

Common options are deep groove ball bearings, angular contact ball bearings, spherical roller bearings and cylindrical roller bearings.

Generally the longest lasting design with proper lubrication and maintenance. Most offer at least 20,000 operating hours before needing replacement.

Rolling element bearings require periodic lubrication and cleaning. Occasional adjustments may be needed as internal clearances increase over time.

Ball Bearings

Ball bearings are a common subtype of rolling element bearing used in industrial motors. They use spherical balls to maintain separation between the inner and outer races. Other rolling element bearings may utilize cylindrical rollers, tapered rollers or needles. Compared to these alternatives, ball bearings excel in applications with high speeds or light loads.

The rolling motion of the balls within a ball bearing creates lower friction than sliding contact in sleeve bearings. This allows them to operate at higher rotational speeds. Proper internal geometry and precise ball sphericity also contribute to their smooth low friction rotation.

Ball bearings are produced in single row or multi-row configurations to support radial, axial or combined loading scenarios.

Journal Bearings (Plain Bearings)

Journal bearings, or plain bearings, use a shaft rotating against a lubricated metal sleeve. Best for heavy radial or combined loads in low to moderate speed applications.

Plain bearings, fluid film bearings or metal-backed bearings are common choices for this type of an electric motor bearing.

With proper mounting and lubrication, these bearings can operate reliably for over a decade before rebuild or replacement. That’s quite a long time in this industry.

As far as maintenance, journal bearings will require oil, grease or process fluid for lubrication. Periodic inspections of clearance and mounting integrity is highly recommended.

These have a lower initial cost than rolling element bearings. The long lifespan offsets rebuild or replacement costs.

Sleeve Bearings

Sleeve bearings, also known as plain bearings, are one of the most common choices for heavy load industrial motor applications. These bearings use a shaft rotating against a replaceable metal sleeve rather than rolling elements. The lubricated sleeve contacts the journal of the shaft, providing free rotation.

Sleeve bearings are best suited for applications with heavy radial loads or combined radial and axial loads. They perform well under shock loading conditions too. Compared to rolling element bearings, sleeve bearings can handle higher levels of contaminants in the lubricant as well.

Their optimal speed range depends on the bearing design and lubrication method, but often tops out between 1,000 to 3,600 RPM in industrial motors.

Magnetic Bearings

Magnetic bearings levitate the shaft using electromagnetic suspension. Benefits include no contact, no lubrication and high speeds.

There are both active and passive magnetic bearings which can help provide design flexibility. You can also integrate different sensors for active control.

Magnetic bearings are often the longest lasting choice, with exceptional examples operating over 30 years without issue!

These will require control electronics and sensors, with minimal other upkeep needs throughout the lifespan of the bearing.

There is a rather high initial cost when it comes to magnetic bearings, though you may save long-term expenses from lack of friction, lubricant and wear issues that are common in other types of bearings.

By understanding the strengths of each major bearing group, you can select the optimal design for your motor’s speed, load capacity and maintenance considerations. Consulting bearing manufacturers is also advised during the selection process.

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