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Bearings - 2017-01-12

NSK’s ceramic-coated bearings for inverter-controlled motors overcomes the issue of electric corrosion

Applicable for use in all general industrial machinery applications, NSK has developed a new range of ceramic-coated bearings. These insulated bearings have been designed to help support the growing adoption of inverter-controlled motors, which are becoming increasingly popular as plants look to reduce electricity bills.

All common machinery parts, including pumps, compressors and fans, are set to benefit from this new development.

Although the use of motors with inverter speed control is expanding, there has been an increase in reports that bearings used for such applications are prone to a specific type of damage called electric corrosion. 

When an electrical current passes along the contact point of bearing races and rolling elements during bearing rotation, sparks are generated in the thin lubricant film, causing the surface to be fused locally into an irregular shape.

One way to prevent electric corrosion is to use non-conductive ceramic balls in the bearings. However, this can have a negative effect on productivity. Another option is to deploy an insulated housing in the motor, but this requires special parts and assembly processes. To overcome these problems, NSK has developed a new ceramic-coated bearing that is insulating, highly productive and compatible with all standard inverter-controlled motors.

An aluminum ceramic material is used to coat the exterior surface of the outer ring, and by combining optimised additives, insulation performance is improved typically by a factor of around 10. In addition, the coating provides excellent heat dissipation, while durability is also improved as a result of a three-fold improvement in film impact resistance due to enhanced bearing elements.

NSK is offering ceramic-coated variants in both deep groove ball bearing and cylindrical roller bearing ranges, encompassing bearing bore diameters from 50 to 110 mm.

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