Whether in traction motors in rail technology, in wind energy or in drive technology: electric motors or generators with frequency inverters are increasingly being used. This trend always carries the risk – with regard to rolling bearings – of voltage occurring between the inner and outer ring. The passage of current can cause serious damage to both the lubricating grease and the rolling elements and raceways, resulting in premature bearing failure. It therefore makes sense to take preventive measures as early as the planning stage to avoid such damage and failures. The Franconian drive specialist Schaeffler now offers improved current-insulating bearings of the J20G series for this purpose.

The new J20G series bearings from Schaeffler have an optimized Insutect A coating. This makes it even easier to avoid the risk of current passage. “Wherever electricity can flow through bearings, good insulation must be provided. Otherwise, parasitic currents can cause significant damage and wear to rolling bearings and lubricants, resulting in unplanned downtime and high maintenance costs,” explains Manuela Bärthlein from Schaeffler's global product management team for current-insulated bearings. ”Our customers benefit from our many years of experience in the field of electrical insulation. With the new bearings, they can significantly increase the reliability of their systems even further.”

The outer sides of the outer and inner rings are coated with Insutect A, an insulating aluminum oxide coating that is applied by means of plasma spraying. To achieve even more reliable protection against current passage, Schaeffler has significantly improved the coating process for the bearings – this ensures even more efficient insulation protection even under demanding operating conditions, such as high humidity. The result is reduced maintenance costs, higher machine availability and operational reliability, as well as an increased service life of the lubricating greases used.

The bearings can withstand DC voltages of at least 3,000 volts and have a higher impedance and an ohmic resistance of at least 250 megohms. The aluminum oxide layer is very hard, wear-resistant and a good heat conductor. In order to meet different requirements, the bearings are available as standard in the variants J20GA, J20GB and J20GI. The J20GB coating thickness offers better protection for higher electrical currents, such as those found in the rail sector, for example. The highest protection is achieved here by bearings with a coated inner ring (J20GI). Further variants are available on request.

The external dimensions of the bearings correspond to the dimensions according to DIN 616, so they have the same dimensions and tolerances as standard bearings and are fully interchangeable. Deep groove ball bearings and cylindrical roller bearings are most commonly used with aluminum oxide coating, but other designs can also be supplied with the coating on request. Bearings with Insutect A coating from Schaeffler fulfill all requirements in terms of operating life, maintenance intervals, operational security and cost-effectiveness.

In addition to bearings with coated rings, Schaeffler also offers hybrid bearings with ceramic rolling elements that provide the highest resistance to current passage. For applications with more demanding requirements or an outside diameter of less than 120 millimeters, the experts at Schaeffler recommend the use of hybrid bearings. Thanks to the comprehensive portfolio, Schaeffler customers can find the right solution for every application.

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