Views:1 Author:Site Editor Publish Time: 2020-06-22 Origin:Site
Insulated bearings refer to the general name of the bearings that can block the passage of electric current and have insulating properties. Its insulation performance is usually ensured by coating a layer of insulating material on the outer ring or inner ring of the bearing using a special process and its rolling elements are made of ceramics.
1. Coating on the Inner or Outer Ring
Special spraying process is adopted for insulated bearing. The outer surface of the bearing is coated with high-quality film, which has strong binding force with the substrate and good insulation performance. It can avoid the electric erosion of the bearing caused by the induced current, prevent the damage caused by the current to the grease, rolling body and raceway, and improve the service life of the bearing. This process is constantly being improved. In insulated bearings, there is a 100 μm thick coating on the outer or inner ring surface, which can withstand a voltage of up to 1000 V DC. The special spraying process can form a layer with uniform thickness and strong adhesion. After further treatment, it can be free from the influence of moisture and humidity.
2. Avoid Damage
Insulated bearings can avoid damage caused by electrical corrosion. Compared with ordinary bearings used in motors can ensure more reliable operation. Compared with other insulation methods, such as shaft or shell insulation, it is more cost-effective and reliable. The dimensions and basic technical characteristics of insulated bearings are the same as those of non-insulated bearings, so they can be interchanged 100%. It is suitable for motors and generators, especially frequency conversion motors.
3. Ceramic Rolling Element
Insulated bearing uses ceramic rolling elements of Si3N4 material. It has excellent insulation performance, its capacitance is basically 40pf, and insulation performance is better than coated bearings. Ceramic rolling elements have excellent wear resistance and low requirements for lubrication, especially suitable for high-speed, low-friction and low-temperature operation. For small size rolling bearings, the use of ceramic rolling element insulated bearings has good economic performance.
The main categories of electrical insulation bearings are: electrical insulation deep groove ball bearings, electrical insulation spherical plain bearings, electrical insulation cylindrical roller bearings, inner or outer ring insulated bearings with oxide coating, hybrid bearing with electric insulated ceramic rolling element.
In the manufacturing process of the motor, even if the production is strictly controlled, it is difficult to completely avoid the magnetic asymmetry between the armature and the rotor. For this kind of asymmetry, the voltage will be generated between the stator, which will generate the current passing through the bearing. The current will produce pits, melting marks, electric erosion file lines, discoloration, wear and other damages on the surfaces of the bearing raceways and rolling elements. In order to block the current 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 certain hardness at the bore and end face of the bearing chamber.
Insulating bearings fundamentally eliminate the shaft current of the motor by blocking the path of the shaft current through the bearing, avoiding damage to the bearing caused by the shaft current under normal operating conditions and causing more serious mechanical failures.