Types of magnetic bearing systems

Magnetic bearings offer a non-contact rotor support system to replace conventional mechanical bearings that physically interface with the shaft and require some form of lubrication.  There are two basic types of magnetic bearing technologies in use today: Passive and Active.  The attractive or repulsive forces of fixed permanent magnets in Passive bearings cause the rotor to remain in the desired position. This type of bearing system is suited for lightly loaded systems, or ones with any significant load in only one axis. In Active magnetic bearing systems, non-contact position sensors monitor shaft position and feed this information to a control system, which regulates current to an actuator to adjust rotor position or provide damping.  While more complex than passive systems, active MBS provide much higher support stiffness and are tunable for optimizing system response.  Also, the existence of requisite position sensors, current sensors and speed sensor, provide a great deal of information for monitoring and diagnostics.