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Guide to Electrically Insulated Bearing Types
Electrically insulated bearings are a special type of bearing designed to prevent current from passing through the bearing, which can cause bearing damage and equipment failure. In electrified equipment, rail transit, wind turbines and other high-voltage environments, current passing through the bearing may cause risks such as electrical erosion, arc damage, and lubricant decomposition. In order to solve this problem, insulated bearings are widely used. This article will introduce several major types of insulated bearings, their advantages and disadvantages, application scenarios, and how to choose the right electrically insulated bearings. Electrically insulated bearings mainly have the following forms.
Ceramic coated insulated bearings are coated with a layer of ceramic material on the outer or inner ring of the bearing to achieve an insulation effect. The coating generally uses ceramic materials such as aluminum oxide or zirconia because of its excellent insulation properties and wear resistance.
Coating process: Using advanced processes such as plasma spraying, the ceramic coating is evenly coated on the outer or inner ring surface of the bearing. The coating thickness is generally between 0.2mm~0.4mm to ensure sufficient insulation strength and wear resistance.
Performance features: Ceramic coating can significantly improve the electrical insulation performance of the bearing and prevent damage caused by current passing through the bearing. At the same time, the ceramic coating also has good chemical stability and anti-aging properties, which can ensure the long-term stable operation of the bearing.
Advantage
Ceramic coating has excellent electrical insulation properties and wear resistance, which can significantly increase the service life of bearings.
The coating thickness is controllable and can be adjusted according to specific needs to meet different insulation requirements.
The coating process is mature, the quality is stable and reliable, and it is suitable for large-scale production.
Application
Ceramic-coated insulated bearings are commonly used in motors and generators, especially in high-power motors. Such bearings can effectively reduce damage to equipment caused by shaft currents. They are also widely used in railway locomotives, wind turbines and other equipment involving the transmission of electrical current.
Shortcoming
Ceramic coatings have high adhesion requirements on the substrate and need to ensure a tight bond between the coating and the substrate.
Special PPS coated insulated bearings
PPS (polyphenylene sulfide) is a polymer material with excellent insulation properties. Special PPS coating improves the formula and process of PPS material to make it have higher insulation resistance and breakdown voltage. Special PPS coating can be coated on the outer or inner ring surface of the bearing to form a dense insulating layer. Special PPS coating has excellent insulation performance and wear resistance, and can maintain stable electrical insulation performance in harsh environments.
Advantages
PPS coating has good insulation performance and chemical stability, and can maintain stable electrical insulation performance in harsh environments.
The coating process is relatively simple and easy to achieve large-scale production.
The coating cost is relatively low and has certain economy.
Disadvantages
The wear resistance of PPS coating may not be as good as that of ceramic coating, and attention should be paid to maintenance during use.
Hybrid ceramic bearings are bearings that use ceramic materials in the rolling element part and traditional steel in the inner and outer rings. This type of bearing achieves electrical insulation by using ceramic balls. Silicon nitride is usually used as the ceramic ball material because it has the characteristics of high strength and low density. Since the resistivity of the ceramic rolling element is much higher than that of the bearing steel, it is difficult for the current to pass through the rolling element, thus achieving electrical insulation of the bearing.
Advantages
Hybrid ceramic bearings combine the advantages of ceramic rolling elements and metal inner and outer rings, with high strength, high wear resistance and good electrical insulation properties.
Suitable for motors and other equipment in harsh environments such as high speed, high temperature and high humidity.
The rolling elements are made of ceramic materials, which have lower friction coefficients and higher speed performance.
Disadvantages
The cost of hybrid ceramic bearings is relatively high and may not be suitable for all application scenarios.
The manufacturing and processing of ceramic rolling elements is difficult, requiring high-precision equipment and processes.
Applications
Hybrid ceramic insulated bearings are widely used in high-speed motors, variable frequency drive motors and precision machinery, especially in equipment with high speed and high efficiency requirements.
Built-in insulation coating bearings
Insulated bearings with built-in insulation are bearings with an insulation layer embedded in the inner or outer ring, usually made of special polymers or composite materials. This insulation prevents the current from passing through the bearing and protects the bearing from the effects of the current. The built-in insulation layer can maintain stable insulation performance under various operating conditions. Such bearings can maintain insulation in high humidity and oily environments. The insulation layer is designed to withstand large mechanical and electrical stresses, thereby extending the service life of the bearing.
Application
Insulated bearings are commonly used in high-power motors, inverter drive systems, and electrified railway locomotives. These bearings are particularly suitable for equipment that needs to operate for a long time in harsh environments.
Selection of insulated bearings
When selecting insulated bearings, it is necessary to comprehensively consider factors such as the current characteristics of the equipment, operating speed, load, environmental conditions, and cost. Ceramic coated bearings are suitable for most motor applications, hybrid ceramic bearings are suitable for high-speed and precision machinery, PPS insulated bearings are suitable for low-load and lightweight equipment, and built-in insulation and insulated ceramic ball bearings are professional solutions for high-performance equipment in extreme environments. By understanding and comparing different types of insulated bearings, engineers and equipment designers can better select appropriate bearings to extend equipment life, improve overall reliability, and reduce maintenance costs.