Time：2021.08.12 Source：Roller Bearings Suppliers
Insulated bearing refers to the general name that can block the current through and the bearing itself has insulating performance.Its insulation performance is usually a special process in the bearing outer ring or inner ring coated with a layer of insulating material, or its rolling body is made of ceramic to ensure.The name of electrical insulation bearing is international bearing code.Outer ring insulated bearing code VL0241, inner ring insulated bearing code VL2071.
The insulating bearing adopts special spraying process, and the outer surface of the bearing is coated with high quality film. The film has strong bonding force with the matrix and good insulation performance. It can avoid the electroerosion effect of induced current on the bearing, prevent the damage caused by current to grease, rolling body and raceway, and improve the service life of the bearing.The process has been continuously improved to insulatingbearings with a 100μm thick coating on the outer or inner ring surfaces to withstand voltages up to 1000 V DC.Special spraying process can form a layer of uniform thickness, strong and uniform adhesion coating, after further treatment to make it can not be affected by moisture and humidity.
Insulated bearings can avoid the damage caused by corrosion, so compared with ordinary bearings in the motor can guarantee more reliable operation.It is more cost-effective and reliable than other insulation methods such as shaft or housing insulation.The external dimensions and basic technical characteristics of insulated bearings are the same as those of non-insulated bearings, so they can be 100 percent interchangeable.Suitable for motor, generator, especially frequency conversion motor is more widely used.Need WSBC 22226 E,click here to learn more.
This type of bearing adopts ceramic rolling body (ball or roller) of Si3N4 material;It has excellent insulating performance, its capacitive capacity is basically 40PF, and its insulating performance is better than that of coated bearings.The dc impedance can reach the range of G ohm at high temperature, and the insulation performance is good.Ceramic rolling body has excellent wear resistance, low requirements for lubrication, especially suitable for high speed, low friction and low temperature operation occasions;Good operating condition under dry friction condition;For small size rolling bearings, ceramic rolling body insulation bearings have good economic performance.
The main categories of electrically insulated bearing products are: electrically insulated deep groove ball bearings, electrically insulated angular contact ball bearings, electrically insulated cylindrical roller bearings, inner or outer ring insulated bearings with oxide coating and mixed bearings with electrically insulated ceramic rollers.
Because of the motor in the process of manufacturing even very strictly control the production is difficult to completely avoid the armature and rotor magnetic asymmetry, on this asymmetry between the stator voltage, it will produce after bearing current, especially more serious in ac motor, the current in the bearing raceway and rolling body surface corrosion pits, weld mark, electric erosion cut, color, wear and damage.Of course, the use of inverter and frequency conversion technology on the motor will also produce this phenomenon.In order to block the current flowing through the bearing, it is necessary to cut off its loop, so that insulated bearings and insulated bearing chambers emerge.The insulating bearing chamber is made of certain hardness insulating material in the bearing chamber hole and end face.
In order to ensure the insulation performance, it is necessary to measure the insulation condition of the insulated bearing, including the insulation resistance, shaft voltage and shaft current of the bearing.The purpose of measuring the motor shaft voltage is to understand the size of the motor shaft current;The purpose of measuring the motor shaft current is to directly get the value of the current flowing through the motor bearing.
Because the shaft current damage mainly occurs in the frame size of 280 and above inverter power supply motor and ordinary large and medium-sized high voltage motor.Therefore, this check is generally only for these types of motor in the first trial production or individual because of the use of the shaft current found to have a serious impact on the bearing of the motor in the improvement of the design.
When measuring, the bearing can be carried out separately, but it is best to install the bearing on the rotating shaft.The general selection of 250V specification insulation resistance meter.The E end of the instrument is connected with the rotating shaft;The insulating part of the bearing (such as the outer ring) is covered with aluminum foil, and the aluminum foil is fixed with bare copper wire binding, and then connected with the L end of the instrument;Or put the insulating bearing into the bearing chamber of the bearing block or the motor end cover, and measure the insulation resistance between the rotating shaft and the bearing block or the motor end cover when there is no electrical path between the bearing block or the motor end cover and the rotating shaft where the insulating bearing is installed.The measuring operation is exactly the same as that of measuring the insulation resistance of the motor and windings to ground.
In order to avoid shaft current burn damage to bearings, effective measures should be taken to isolate shaft current.Click here to learn more about WSBC 22310 E.
For large motors with independent bearing housings at both ends, isolation gaskets made of insulating material can be placed between the bearing housings and the metal base.For ordinary bearing and housing assembly into one motor, it is generally in one end (often arranged in the non-spindle extension end) use insulated bearings, for high requirements of the occasion, both ends are installed with insulated bearings.The insulation bearing used is usually attached (usually coated) insulation layer on the outer ring, and in some cases, both the inner and outer rings are attached with insulation layer.
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