Electric motors, generators and associated equipment are at risk when an electric current passes through a bearing. This can damage the contact surfaces of rolling elements and raceways in the bearing (electrical erosion) and rapidly degrade the grease. An additional risk in electric motors and generators comes from high frequency currents due to the inherent stray capacitance. The risk of damage increases if the application uses a frequency converter.
INSOCOAT bearings (fig. 1) are designed to prevent current from passing through the bearing. The bearings are a very cost-effective solution compared with other insulation methods. By integrating the insulating properties into the bearing, INSOCOAT bearings can improve reliability and increase machine uptime by virtually eliminating the problem of electrical erosion.
An INSOCOAT bearing is a standard bearing that has the external surfaces of its inner or outer ring plasma-sprayed with an aluminium oxide to form a coating. The coating is sealed with a resin to protect against the conductive effects of water and moisture.
The basic coating can withstand voltages up to 1 000 V DC. However, coatings to withstand voltages up to 2 000, or even 3 000 V DC, can be supplied on request.
INSOCOAT bearings with a coated outer ring
INSOCOAT bearings typically have the external surfaces of the outer ring coated with aluminium oxide. These bearings are identified by the designation suffix VL0241.
INSOCOAT bearings with a coated inner ring
INSOCOAT bearings that have the external surfaces of the inner ring coated are identified by the designation suffix VL2071. These bearings provide enhanced protection against high frequency electric currents due to the smaller coated surface area of the inner ring compared to the outer ring.
The standard assortment of INSOCOAT bearings listed here constitutes the most commonly used sizes and variants of:
- single row deep groove ball bearings
- single row cylindrical roller bearings
For bearing types and sizes not listed in the product tables, contact the SKF application engineering service.
For applications where smaller bearings than those listed are needed, SKF recommends using SKF Hybrid bearings.