06/28/2022
These next following pictures are deep groove ball bearing, self-aligning roller bearing, conical roller bearing, linear electrically-insulated bearing, and cylindrical roller bearing.
To ensure smooth, trouble-free operation, it is necessary to prevent the bearing from the electric current passage. The contact areas between housing, outer ring, rolling elements, inner ring, and shaft can act as electric contacts. The resulting arcs – characterized by very high temperatures like that produced by melting and welding processes – will damage rolling elements as well as raceways of bearing rings.
The passage of electric current through rolling bearings can lead to damage in a relatively short period. Small craters caused by an electric current passage which have been tolerated occasionally in the past are no longer acceptable. As a consequence, some bearing leaders of the world developed their electric current insulating bearings products, which have special coated outer rings with a ceramic electrically-insulated coating for a breakdown voltage up to 1,000 V or even higher.
The technical process that overlays the ceramic electrically-insulated coating is called plasma spray, which fuses the ceramic powder with heat from the plasma arc and sprays the melting or softened ceramic particles onto the surface of bearing rings. Today, current insulating bearings have been substantially applied on some crucial industrial products like traction motors, wind turbine generators, etc., and exhibit a very good function effect. Recent reports, however, have shown that after years of application in the field, although the service life of the current insulating bearings is remarkably extended as compared to non-insulation coating bearings, still some random passage of electric current happens and leads to damage to bearings, even there is a ceramic coating on the bearing rings.
Beijing Langqiao Material Technology Co. (LQ) is committed to exploring the nature of ceramic coating’s failure. By combining the plasma spray specialists with bearing manufacturers, LQ did some in-depth research on the issue and came to the conclusion that three causes may result in such a failure:
1. The nature of porosity remained in the structure of plasma sprayed coating.
2. The copper in the ceramic coating which introduced during the thermal plasma spraying process from the copper electrode in the plasma torch.
3. Ceramic coating thickness matters
With the above understanding in mind, LQ improved its plasma spraying process by modifying the plasma spraying equipment and parameters recipes and marketed its new line of current insulating bearings SAT series.
LQ’s SAT series of electrical current insulating bearings are divided into ordinary models and special models according to insulation grade and insulation mode. The ordinary models are SAT-10, SAT-10N, and SAT-20. The special models are SAT-10T and SAT-05. If there are special requirements for insulation grade, insulation method (outer ring or inner ring insulation), retainer material, and structure, we can customize it on demand.
