Improved current-insulated bearings from Schaeffler
Rolling bearings with optimized coating for improved protection against current passage
AS the use of electric motors or generators with frequency converters increasingly becomes the norm, this trend also introduces the risk of electrical voltage developing between the inner and outer rings of rolling bearings. Current passage can significantly damage lubricants, rolling elements, and raceways, leading to premature bearing failure. As a result, Schaeffler have now introduced improved current-insulated bearings from the J20G series to help mitigate this risk.
The new J20G series bearings have an optimized Insutect A coating, offering even greater protection against the risk of current passage. ‘Wherever current can flow through bearings, robust insulation is essential. Without it, parasitic currents can cause significant damage and wear to rolling bearings and lubricants, resulting in unplanned downtime and high maintenance costs,’ explained Manuela Baerthlein from global product management for current-insulated bearings at Schaeffler. ‘With these new bearings, our customers benefit from our long-standing experience in current insulation and can significantly enhance the reliability of their systems.’
The outer surfaces of the outer and inner rings are coated with Insutect A, an insulating aluminium oxide coating applied using plasma spraying. Schaeffler have 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 3,000V and exhibit a higher impedance and an ohmic resistance of at least 250 megaohms. The aluminium oxide coating is extremely hard, resistant to wear, and a good conductor of heat. The bearings are available as standard in the J20GA, J20GB, and J20GI variants to meet diverse requirements. The highest level of protection is achieved with bearings that feature a coated inner ring (J20GI). Other variants are available upon request.
The external dimensions of the bearings conform to the dimensions specified in DIN 616 standards, which means they have the same dimensions and tolerances as standard bearings and offer seamless interchangeability. Deep-groove ball bearings and cylindrical roller bearings are most commonly used with aluminium oxide coatings, although other bearing designs are also available with the coating by agreement. Schaeffler say Insutect A-coated bearings meet all requirements relating to service life, maintenance intervals, operational safety, and cost-efficiency.
