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Detailed explanation of the application of insulated bearings in motors

Update:15-12-2020
Summary:   Electrically insulated bearings can prevent damage caused by electrical corrosion, so compared with ordinary bearings...
  Electrically insulated bearings can prevent damage caused by electrical corrosion, so compared with ordinary bearings, they can be used in motors to ensure more reliable operation. Compared with other insulation methods, such as shaft or housing insulation, it is more cost-effective and reliable. The outer dimensions and basic technical characteristics of insulated bearings are the same as non-insulated bearings, so they can be 100% interchanged. It is suitable for motors and generators, especially variable frequency motors.
The application of insulated bearings in motors, the reasons and hazards of the composition of motor shaft voltage and bearing currents. During motor operation, any imbalance in the stator and rotor magnetic circuits or the phase currents of the coiled shaft can produce the flux linkage of the rotating system . When the shaft rotates, these magnetic links can generate a potential difference across the shaft. This potential difference is called the shaft voltage. The shaft voltage can encourage circulating current in the loop (closed circuit) formed by the shaft and the casing through the bearings at both ends. This current is called the shaft current.
Shaft current Shaft current In addition, there is more residual magnetism in the dead center of the rotor. Regarding the wound rotor motor, if two or more winding points are caused to the rotor dead center or short circuit to the shaft, shaft voltage and shaft current will also be generated. The size of the bearing current is different from that of the motor. The structure, the power of the motor, the amplitude of the driving voltage, the pulse rise time, the length of the cable and other factors are related.
  The greater the power of the motor, the higher the drive voltage, the steeper the rising edge of the drive voltage, and the shorter the cable, the greater the bearing current. Measures to block the shaft current-using insulated bearings In order to prevent the shaft current from damaging the bearing, effective measures should be taken to isolate the shaft current. For large motors with independent bearing housings at both ends, insulation can be placed between the bearing housing and the metal base Isolation gasket made of data.
  As for motors with ordinary bearings and housings assembling into one, insulated bearings are generally used at one end (often arranged at the non-spindle extension end). For places with higher requirements, insulated bearings are installed at both ends. The insulated bearings used are usually the outer ring with an additional (usually coated) insulation layer, and some places will also use the inner and outer ring with an additional insulation layer.