Whether in traction motors for rail transport, wind energy systems, or drive technology, the use of electric motors or generators with frequency converters is increasingly becoming the norm. However, this trend also entails the risk of electrical voltage developing between the inner and outer rings of roller bearings. Current passage can significantly damage lubricants, rolling elements, and raceways, leading to premature bearing failure. As a result, implementing measures to prevent such damage and failures at the early planning stage is advisable. A key element here: current-insulating bearings.

“Wherever current can flow through bearings, robust insulation is essential. Without it, parasitic currents can cause significant damage and wear to roller bearings and lubricants, resulting in unplanned downtime and high maintenance costs,” explains Manuela Baerthlein from Global Product Management for current-insulated bearings at Schaeffler.

3,000 volts – doesn’t matter!

The outer surfaces of the outer and inner rings of these special Schaeffler bearings are coated with Insutect A, an insulating aluminum oxide coating applied using plasma spraying. Schaeffler has refined the bearing coating process for enhanced reliable protection against current passage to provide a more efficient insulation protection, even under challenging operating conditions such as high humidity. The result is reduced maintenance costs, increased machine availability and operational safety, and an extended grease service life.

The bearings can withstand direct voltages of at least 3,000 volts and exhibit a higher impedance and an ohmic resistance of at least 250 megaohms. The aluminum oxide coating is extremely hard, resistant to wear, and a good conductor of heat. In addition to bearings with coated rings, Schaeffler offers hybrid bearings with ceramic rolling elements, which offer the highest resistance to current passage.

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