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AUBEARING Electrically Insulated Bearings
Electrically insulated bearings use a special spraying process to coat the outer ring surface with a high-quality film (insulating coating). The film has a strong bond with the substrate and good insulation performance, which can avoid the electro-corrosion of the bearing by the induced current, prevent the damage of the current to the grease, rolling elements and raceways, and increase the service life of the bearing. AUBEARING continues to improve this process. In the insulating bearing, there is a coating with a thickness of 100μm on the surface of the outer or inner ring, which can withstand a voltage of 500-3000V DC. The special spraying process can form a coating with uniform thickness and strong adhesion, which can be protected from moisture and humidity after further treatment.
Electrically insulated bearings avoid damage caused by electrical corrosion, which can cause corrosion pits, weld marks, electrical scratches, discoloration, wear and damage to the raceway and rolling element surfaces. Therefore, compared with ordinary bearings, they can be used in motors to ensure reliable operation. Compared with other insulation methods such as shaft insulation, housing insulation, ceramic bearings and hybrid ceramic bearings, it is cost-effective and reliable. The overall dimensions and basic technical characteristics of insulated bearings are the same as non-insulated bearings, so they can be cross-interchangeable. Suitable for motors and generators, especially variable frequency motors bearing.
Electrically insulated bearing coating materials
AUBEARING is a Chinese bearing manufacturer with than 10 years of experience in the design and research of electrically insulated bearings, relying on rich experience in special spraying processes. The outer surface of the inner or outer ring of the bearing adopts advanced plasma spraying process to obtain excellent surface quality. Compared with other insulation methods, the insulating aluminum oxide coating solution is cost-effective.
Some other typical insulating bearing materials include ceramic, polytetrafluoroethylene (PTFE), etc. Ceramics are widely used in the bearing industry because they are as hard as diamond, as wear-resistant as gold and have outstanding insulation properties. PTFE is widely used due to its excellent corrosion resistance and strong insulation. According to actual needs, designers and engineers can also choose other special materials to construct insulating bearings. For example, in high temperature, high pressure or harsh environment, expensive but highly corrosion-resistant metals such as stainless steel or titanium can be selected as the first choice.
Regardless of the environment, the material selection of insulating bearings plays a key role in determining their performance and life. In addition to fully considering the purpose of the bearing, AUBEARING’s designers and engineers must also comprehensively weigh the environmental conditions and various material properties to provide you with the best solution.
Electrical insulation bearing grade
The good corrosion resistance of electrical insulation bearings ensures that they can be applied to various industrial equipment such as compressors, water pumps, crushers, mines, machinery industry, petrochemical industry, generators and other harsh environments with corrosive media; through high resistance, they can effectively avoid current damage to bearings and meet the insulation requirements of bearings in various power equipment. The insulation grade of motor bearings mainly includes three categories:
1. General insulation: suitable for ordinary equipment and environment, with insulation resistance greater than 50MΩ.
2. High resistance insulation: suitable for high-demand equipment and environment, such as humidity, high temperature, high pressure, etc., with insulation resistance greater than 500MΩ.
3. Ultra-high resistance insulation: suitable for special environments, such as chemical industry, nuclear power, etc., with insulation resistance greater than 1000MΩ.
Selecting the appropriate insulation grade of motor bearings can improve the safety and stability of equipment, reduce the failure rate, extend the life of equipment, and also help protect the safety of staff.
Electrically insulated bearing types
AUBEARING can supply 500-3000V DC coated insulated bearings according to customer requirements. The most common suffix codes for insulated bearings internationally are: VL0241, VL2071, VA3091, J20A, J20AA, J20B, J20C, SQ77, SQ77E, etc. Among them, VL0241, VA3091, J20AA, J20A, J20B, SQ77, V3031A are outer ring insulated bearings, and VL2071, J20C, SQ77E, V3031B are inner ring insulated bearings.
VL0241 and VA3091 indicate SKF (INSOCOAT) outer ring bearings with insulating coating. J20AA, J20A, J20B indicate FAG brand outer ring bearings with insulating coating. SQ77 indicates NKE outer ring bearings with insulating coating.
Deep groove ball bearings
Compared with other types of the same specifications and dimensions, deep groove ball electrically insulated bearings have a small friction coefficient, a higher limit speed, and good insulation performance. They can avoid the electro-corrosion of the induced current on the shaft, prevent the current from damaging the grease, rolling elements, and raceways, and increase the service life of the bearings.
Cylindrical roller bearings
The rollers and raceways of cylindrical roller insulating bearings are in line contact or repaired line contact, with large radial load capacity, suitable for bearing heavy loads and impact loads. This type of bearing has good insulation performance and prevents the occurrence of current corrosion in the motor shaft.
Spherical roller bearings
Spherical roller electrically insulated bearings have two rows of rollers, which mainly bear radial loads, and can also bear axial loads in any direction. They have high radial load capacity and are particularly suitable for working under heavy loads or vibration loads, but cannot bear pure axial loads and have good impact resistance.
Tapered roller bearings
The ability of a single-row tapered roller bearing to bear axial loads depends on the contact angle, that is, the angle of the outer ring raceway. The larger the angle, the greater the axial load capacity. Widely used in automobile, rolling mill, mining, plastic machinery and other industries.
Angular contact bearings
Angular contact ball bearings mainly bear large unidirectional axial loads. The larger the contact angle, the greater the load bearing capacity. The contact angle is generally divided into 15°, 30°, and 40°.
Hybrid ceramic bearings
Hybrid ceramic bearing configuration: inner and outer ring bearing steel/stainless steel + ceramic ball + PA66/stainless steel cage + 2RS/2Z. It has the characteristics of high temperature resistance. The temperature of ordinary bearings is about 160 degrees. Ceramic balls can reach than 220 degrees. The speed is high, it has the characteristics of oil-free self-lubrication, small friction coefficient, and can be used in conductive environments.
FAQ
Q: What is the difference between insulated bearings and ordinary bearings?
A: The biggest difference between insulated bearings and ordinary bearings is insulation. In addition to basic technical features and dimensions, insulated bearings and ordinary bearings are very different in appearance and usage characteristics. The appearance of ordinary bearings is the metallic color of bearing steel. The inner ring or outer ring of insulated bearings is coated with an insulating coating on the surface, so the color is different from that of ordinary bearings. Generally, the inner ring or outer ring is black, white or gray.
Q: Under what circumstances should insulated bearings be used?
A: Normal power grid power supply has no high-frequency voltage and current components, and insulated bearings are generally not used. Only high-voltage motors and large motors such as those with specifications above 400 are used. However, now they are all powered by variable frequency power supplies. Since the power quality contains many high-frequency components, the motor shaft current increases. Therefore, this issue should be considered for specifications above 400, and even for specifications smaller than this, insulated bearings are considered to be installed according to the usage conditions. For example, the main motors used in electric vehicles and electric rail locomotives are generally around 100KW, and insulated bearings must be used (or other insulating structures are used to ensure that the shaft current does not flow).
Q: How to indicate the insulation of bearings?
A: The indication method of insulated bearing models is the same as that of ordinary bearings, with only some additional suffixes, refer to the international bearing code. SKF outer ring insulated bearing code: VL0241, VA3091. SKF inner ring insulated bearing code: VL2071. FAG outer ring insulated bearing code: J20AA, J20A, J20AB, J20B. FAG inner ring insulated bearing code: J20C. AUBEARING outer ring insulated bearing code: V3031A, AUBEARING inner ring insulated bearing code: V3031B.
Q: Why do insulated bearings of motors lock?
A: 1) Improper assembly; improper matching of the outer ring of the bearing and the bearing seat hole or the inner ring of the bearing and the shaft during assembly, improper bearing heating temperature control during assembly, or improper bearing clearance adjustment during assembly will increase the bearing temperature, causing the bearing to wear and damage, thus causing locking.
2) Oil seal problem; If there is a problem with the quality of the oil seal, it will cause the oil seal to be damaged by dry friction, causing the bearing to heat up too high in a short time. At this time, it is necessary to replace the oil seal and then test run to solve this problem.
3) Clearance problem; During the use of the equipment, due to the failure of the transmission device used, in order not to affect production, the short shaft parts need to be replaced. However, sometimes the temperature of the short shaft bearing rises sharply within less than 10 minutes of operation, and the short shaft is locked.
Q: What are the main factors to consider when selecting the type of insulating bearing?
A: When selecting insulating bearings, the bearing type, load, clearance, installation, disassembly, and size are generally considered. importantly, the design life of the bearing and the blocking voltage of the bearing insulation coating and the endurance life of the current. When selecting bearings, the grease life, wear, noise, etc. caused by grease aging also need to be fully studied. Further, according to different uses, it is necessary to select requirements for accuracy, cage structure, insulation coating material, grease, etc.