Basic knowledge of insulated bearings

Insulated Bearings Introduction The most effective solution to bearing galvanic corrosion problems is the use of insulated bearings. Common insulated bearings are roughly divided into three types: surface-coated ceramic, surface-coated resin, and ceramic rolling elements. Surface-coated ceramics are the most versatile. What material is the insulating layer of an insulated bearing? One of the main features of the insulated bearing is that there is a layer of 50-200μm thick ceramic coating on the surface, which is responsible for the electrical insulation function and can resist the electrical flashover generated under 1000V voltage, and the thicker coating can resist more than 1000V of high voltage discharge. Jiuxing Bearing Technology Co., Ltd. has advanced bearing production equipment and technology. Relying on domestic technical experts, it is the first to produce high-performance and cost-effective insulating bearings in China. All technical indicators have reached the international advanced level and have been well received by users. Classification of Insulated Bearings Deep Groove Ball Insulated Bearings Angular Contact Ball Insulated Bearings Cylindrical Roller Insulated Bearings Tapered Roller Insulated Bearings Thrust Insulated Bearings, etc. Product Features The process has been continuously improved. In insulated bearings, there is a layer on the surface of the outer ring or inner ring. 100μm thick coating, can withstand voltages up to 1000V DC. A special spraying process creates a coating of uniform thickness and extremely strong adhesion, which is further treated to make it impervious to moisture and humidity. •Usage •Suitable for motors, generators, especially variable frequency motors are more widely used.

The principle of bearing insulation • Select insulated bearings • Insulated bearings: Insulated bearings are outer ring coating, inner ring coating and ceramic material rolling elements. The first two coatings are to coat the ceramic material on the bearing surface by plasma spraying, and this coating still maintains its insulating properties in a humid environment; the ceramic material rolling element insulating bearing, that is, the rolling element is made of ceramic material, has excellent performance. current resistance capability. Generally, the size of the motor is insulated with bearings. This needs to be determined according to the power state of the motor. The normal grid power supply has no high-frequency voltage and current components. Generally, insulating bearings are not used. Only high-voltage motors and large motors such as 400 and above are used. Even without it. But now the frequency conversion power supply, because the quality of the power supply contains a lot of high-frequency components, resulting in an increase in the motor shaft current, so this problem should be considered for normalization above 400, and even the smallest specification should be installed according to the usage conditions. Bearings, such as the main motors used in electric vehicles, electric rail locomotives, etc. are generally about 100KW, and insulating bearings must be used (or other insulating structures are used to ensure that the shaft current does not flow).

•Size range of insulated bearings•Electrically insulated deep groove ball bearings•Inner diameter dimension range: 40mm～140mm•Outer diameter dimension range: 80mm～300mm•Width dimension range: 18mm～62mm•Electrically insulated angular contact ball bearings•Inner diameter dimension range: 40mm～140mm•Outer diameter dimension range: 80mm～300mm•Width dimension range: 18mm～62mm•Electrically insulating cylindrical roller bearing•Inner diameter dimension range: 45mm～140mm•Outer diameter dimension range: 100mm～300mm•Width dimension range: 25mm ～62mm Insulated Bearing Application Fields Electric Power Industry: Cylindrical Roller Insulated Bearings for Generators: Wind Turbines, Hydrogenerators, Thermal Power Generators Railway Industry: Cylindrical Roller Insulated Bearings for Traction Motors of Diesel Locomotives: Used in Locomotives, etc. •Mechanical and metallurgical industry: insulating bearings for high-power variable frequency motors: used in cranes, textile machines, printing presses, iron-making equipment, steel-making equipment, steel rolling equipment, cutting equipment, coking equipment, smelting equipment, etc. Mining machinery industry: Insulated bearings for high-power and high-voltage motors are used in mining machines, coal preparation machines, coal washing machines, crushers, ball mills, grinders, and sand mills. •Petrochemical industry: insulating bearings for high-power explosion-proof motors: used in compressors, etc. •High-voltage motors can be used to drive various machinery. Such as compressors, pumps, crushers, cutting machine tools, transportation machinery and other equipment, for mining, machinery industry, petrochemical industry, generators and other industries as prime movers.

Motors used to drive blowers, coal mills, rolling mills, and hoists should indicate their use and technical requirements when ordering, and adopt special designs to ensure reliable operation. The outer surface is sprayed with high-quality coating, the coating has strong bonding force with the substrate, and has good insulation performance, which can avoid the galvanic corrosion of the bearing by the induced current, prevent the current damage to the grease, rolling elements and raceways, and improve the bearing performance. service life. Technical parameters The dimensions and technical characteristics of insulated bearings are the same as those of conventional bearings, so they can be completely interchanged. Insulation resistance should be at least greater than 100MΩ measured at 500VDC.

At least greater than 50MΩ at 1000VDC. PROCESS CHARACTERISTICS • The process is constantly being improved. This plan includes, for example, further improvements in mechanical stability and breakdown voltage limits. In insulated bearings, there is a 100μm thick coating on the outer or inner ring surface, which can withstand voltages up to 1000 V DC. A special spray process results in a coating of uniform thickness and extremely strong adhesion, which is then further treated to make it impervious to moisture and humidity. • Electrically insulated bearings have a longer service life than other standard non-insulated bearings. Because they are completely immune to damage caused by overcurrent, they have a very high operational reliability. Insulated bearings and non-insulated bearings have the same size and load capacity, and are completely interchangeable. Advantages of Insulated Bearings • Electrically insulated bearings can avoid damage caused by electrical corrosion, so compared with ordinary bearings, they can be used in motors to ensure more reliable operation. It is more cost effective and reliable than other insulation methods such as shaft or housing insulation. The outer dimensions and basic technical characteristics of insulated bearings are the same as those of non-insulated bearings, so they are 100% interchangeable.

How does the electrical insulating bearing achieve the insulating function 1. Even if the motor is very strict in the manufacturing process, it is difficult to completely avoid the magnetic asymmetry between the armature and the rotor. This asymmetry will generate a voltage between the stators. The current passing through this time will be generated, especially in the AC motor. The current will cause corrosion pits, melting marks, electrical corrosion, discoloration, wear and other damage on the bearing raceway and rolling element surface. Of course, motors that use inverter and frequency conversion technology will also produce this phenomenon. In order to block this current from flowing through the bearing, it is necessary to cut off its circuit, so the insulated bearing and the insulated bearing chamber came into being. The insulating bearing chamber is made of insulating material with a certain hardness in the bore and end face of the bearing chamber. 2. With the development of high-speed railway and underground rail transit, more and more new technologies are applied to this efficient vehicle , For example, the development of electrically insulated bearings is a new type of bearing product produced in order to adapt to the development of high-speed railways and other environments. The idea of ​​making insulated bearings has long been studied as an important scientific and technological subject.


• When the high-speed railway and underground rail transit are in operation, it is inevitable to adopt the design of electrical connection from above, and the damage caused by current corrosion to the bearing greatly affects the life of the bearing. How to solve the problem of electrical corrosion on the bearing destruction is an important issue facing. The idea of ​​insulated bearings is also applied. There are three common styles of insulated bearings so far: bearings with an insulating layer on the inner ring and an insulating layer on the outer ring and hybrid ceramic ball bearings. Installation method of insulated bearing 1. Use special tools for bearing installation and disassembly. Advanced installation tools can avoid bearing damage caused by improper tools and operation during installation. For example, when installing the bearing, the staff used the copper rod knocking method, which is easy to cause uneven axial force on the bearing, causing deformation of the cage, damage to the rolling elements, and large clearance. The copper powder flies into the bearing cage, which is easy to cause bearing failure.

2. Do a good job of bearing inspection before installation. For old bearings, it is necessary to check whether there are burrs, scratches and cracks on the surface of the ball (column). Whether the radial clearance and axial clearance of the old bearing are qualified, generally only the radial clearance is measured. For new bearings, first check that the bearing type is correct. Refer to Table 1 for the radial clearance standards of rolling bearings. For example: Model 6318 deep groove ball bearing, the inner diameter of the bearing is 90mm, the radial clearance range is 0.016~0.046mm, and the maximum wear amount of the bearing can also be found to be 0.25mm.

3. Check the matching size of the bearing and the rotor shaft When the motor is assembled, it is also necessary to carefully check the matching size of the bearing and the rotor shaft when the bearing is installed (Table 2), and the matching size of the bearing outer ring and the end cover hole. Fourth, control the amount of oil in the bearing and the bearing room. Excessive oil in the bearing and the box will cause the bearing rolling element to slip, causing the rolling element to change from rolling friction to sliding friction, and damage the bearing rolling element. The free space in the box is small, the operating temperature of the bearing will rise, the degree of lubricating grease will decrease, the lubricating oil film of the rolling element will become thinner, and the lubrication conditions will be poor, which will easily cause abnormal noise of the bearing, slip on the surface, and shorten the life of the bearing.


Generally, there is a bearing oil chamber on the side of the motor end cover (except for motors designed with double-sealed bearings). According to the speed of the motor, the amount of oil that can be filled in the bearing chamber can be implemented according to the following standards: when the motor speed is less than 1500r/min, the amount of oil added to the bearing is the same as that of the bearing. 2/3 of the chamber volume. When the speed is between 1500~3000r/min, it is 1/2 of the bearing chamber volume. When the speed is >3000r/min, it should be less than or equal to 1/3 of the bearing volume. In the actual working process, for the bearings running at high temperature and high speed, the bearings with sealing surfaces should be used as little as possible, the oil storage capacity of the motor oil cap should be increased, and the oil nozzles should be installed to improve the operating life of the motor bearings.

5. Pay attention to ensure the insulation is intact. For bearings with an insulating design on the outer ring, care should be taken to ensure that the insulation is intact. If the bearing insulation is damaged during installation, the very thin bearing oil film will be broken down by the shaft voltage. After the oil film is broken down, not only the lubrication conditions of the rolling elements will be bad, but also the electric sparks generated will cause electrical corrosion to the rolling elements of the bearing, causing rolling elements. The surface is not smooth, which accelerates the wear of the bearing. SKF, FAG insulated bearing suffix code and data parameters • SKF process insulated bearing: insulated bearings with a coated outer ring usually have the outer diameter surface and end face of the outer ring with an alumina coating. This bearing suffix is ​​represented by VL0241; with coating Insulated bearing with inner ring bore and end face This type suffix VL0271 indicates that this bearing can improve the protection against high frequency current.

•FAG insulated bearings provide four types, which can supply deep groove ball bearings and cylindrical roller bearings respectively: •J20B suffix: up to 500V voltage, outer ring coating <100μm, can provide products in the range of 70-1400mm; '•J20A Suffix: withstand voltage up to 1000V, outer ring coating> 200μm, provide products in the range of 70-1400mm; J20AA suffix: withstand 1000V voltage, outer ring coating ≈ 200μm, provide products in the range of 70-500mm; J20C suffix: Can withstand 1000V voltage, inner ring coating ≈ 200μm, provide bearing products in the range of 70-340mm Prefix HC: Hybrid ceramic bearing, rolling elements are made of ceramic materials. When ordering FAG process insulated bearing products, it is necessary to specify the bearing products to be ordered. Models, such as 6220-2RSR-J20AA-C3, indicate deep groove ball bearings with seals.


Bearing products with C3 clearance and insulating coating on the outer ring; NU214-E-M1-F1-J20B-C4: cylindrical roller bearing with brass cage, C4 clearance, electrically insulating bearing with thin coating; • 6330-J20C: Open deep groove ball bearing with coated inner ring. Precautions for the use of insulated bearings•Compared with general mechanical parts, the precision of rolling bearings is higher, so be careful when using them. • 1. Keep the bearing and its surroundings clean. • 2. Be careful and careful when using it. It will cause damage to the bearing, such as scars, indentations, and fractures. • 3. Use suitable tools • 4. Pay attention to the rust prevention of the bearing. • Avoid using it in a humid place, so as not to make the sweat stick, you should wear gloves.

• 5. Users should be familiar with bearings • 6. Operational specifications for formulating policies and use • Bearing storage Cleaning of bearings and surrounding areas • Inspection of the dimensions and processing quality of installation parts • Installation operations • Post-installation inspections • Dismantling operations • Maintenance Maintenance (periodic inspection) • Lubricant replenishment