Magnetic bearings position sensors

In a radial active magnetic bearing, the rotor is held in position by electromagnets located on the stator (Figure 6-3). The rotor-to-stator position is constantly monitored by sensors that communicate with the electronic control system. If the rotor deviates from its position, the control system adjusts the current flow to the electromagnets to return the rotor back to its proper position. 

An active magnetic axial bearing consists of two stators and a rotor disk (Figure 6-4). A sensor located at the end of the shaft monitors and maintains the rotor position between the two stators. The principle of operation is the same for both axial and radial bearings any deviation from the normal position of the rotor is communicated to the electronic control system, which adjusts the electric current going to the electromagnets to correct the rotor position. 

When oil film breakdown has occured at the rolling surface during bearing operation, the ceramic balls are electrically Insulated. Therefore, electrical current flows only when oil film breakdown has occurred between the steel ball and the raceway surface. A magnet sensor is installed at the inner ring and retainer, and this is used to ascertain the circumferential angular position when oil film breakdown has occurred. 

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