NSK bearings with ceramic coating benefit VSD users

Energy-efficient VSDs are becoming increasingly popular in a host of industrial machines, systems and equipment. The use of VSDs is particularly economical when different power levels are required in response to variable demand. However, frequency regulation calls for bearings that fit a different set of requirements, largely because there is always the risk of parasitic current reaching the driven components via the motor shaft and bearings. This current can cause damage to the bearings from phenomena such as ripple formation and the melting of running surfaces. The function and service life of driven components can also be impaired by the passage of current.

Design engineers are able to counteract these relatively common problems by using deep groove ball bearings with a ceramic coating on the outer ring. The insulating effect of the coating stops current transfer and, subsequently, prevents bearing damage.

Based on an extensive series of tests, NSK has enhanced the ceramic coating used until now, a move that has resulted in two prime advantages. Firstly, the insulating effect of the coating is up to 10 times greater. Secondly, the impact resistance of the normally very brittle ceramic is now more than three times that of ceramic coatings found on conventional bearings. The bearings thus achieve significantly longer service life.

A further benefit is that the optimised ceramic coating provides better dissipation of the heat generated in the bearing as rotation occurs, again contributing to extended service life.

NSK’s range of ceramic-coated deep groove ball bearings is described in a new catalogue entitled ‘Bearings for Electric Motors’, which is available in print or as a PDF download at: http://www.nsk-literature.com/en/industrial-motor-bearings/