Magnetic bearings use an electromagnet to provide non-contacting, friction-free motion in rotary applications.  They are constructed of a rotating and a stationary part (rotor and stator, respectively) separated by an air gap.  Magnetic bearings operate by applying an electric current to ferromagnetic materials used in both the rotor and stator, creating a magnetic flux path that includes the rotor, stator, and air gap.  Magnetic bearings do not require lubrication, and are virtually maintenance-free.  They are available in two different functional types: active (AMB) and passive (PMB).