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Insulating bearings for electric motors
2018-06-13
The impetus for the development of current-insulating bearings was the presence of parasitic stray currents in electric motors, electric generators and associated equipment. A normal bearing is a good conductor of electric current, and stray currents passing through it contribute to erosion on the rolling bodies and raceways. They also cause changes in the properties of lubricants. All these factors combine to accelerate wear and early failure of the bearing or bearing unit. The use of frequency converters in electric motors, which improve the smoothness and efficiency of the electric motor, significantly increases the amount of stray currents flowing through the bearing.
Initially, they tried to combat this problem by electrical isolation of the shaft and housing of electrical equipment. But this is a very expensive process. And the leading bearing companies have been able to offer solutions to this problem.
The first and most common solution is to apply a ceramic coating to the inner and outer surfaces of the bearing and to the seal. The application of an insulating coating on the bearing rings prevents the direct passage of currents through the bearing, while the application of a coating on the sealing elements prevents the passage of currents through the condensates. As the thickness of the applied ceramic layer increases, the electrical insulation properties of the bearings increase. This method of bearing insulation is the cheapest and most common and can be applied to any type of bearing. But since radial ball bearings and radial roller bearings with cylindrical rollers are mainly used in electric motors and electric generators, electrically insulated bearings of these types are mostly offered. All of the world's leading manufacturers have their own range of these bearings.
Hybrid bearings with ceramic rollers and all-ceramic bearings in which silicon nitride is used as a ceramic with excellent insulating properties are also current-insulating bearings.
Many leading companies in the bearing industry are further developing new technologies in the field of bearing current isolation in order to improve it and make it cheaper.
