Magneticbearing

A magnetic bearing is a type of air bearing that uses magnetic forces to support a rotating shaft without physical contact. It operates by creating a magnetic field that attracts a ferromagnetic or magnetized surface of the bearing, holding the shaft in a precise position while eliminating friction.

The concept dates back to the early 20th century, but practical magnetic bearings were developed during World War II for high-speed turbine applications. Modern research has expanded their use to precision instruments, industrial robots, and aerospace technology. Modern designs typically employ a rotating magnet mounted on the rotating shaft and a stationary magnet or magnetic circuit on the bearing housing. The magnetic attraction is carefully balanced to provide radial, axial, or hybrid support.

Key advantages include virtually zero wear, extremely low vibration, and very high rotational speeds that can exceed 100,000 rpm. Disadvantages are the need for precise control of magnetic flux, sensitivity to temperature variation, and a requirement for close tolerances in the fabrication of the magnetic components. Sensors and electronic feedback systems are usually incorporated to maintain centering and stability.

Typical applications are found in high‑speed milling machines, semiconductor lithography tools, superconducting maglev test rigs, and precision goniometers. Researchers are exploring liquid‑metal lubricated magnetic bearings as a way to combine the low friction of magnetic bearings with the temperature‑resistant properties of liquid metals. Hybrid magnetic gear systems that combine an electromagnetic torque generator with a magnetic bearing are also under development for use in robotics and space propulsion.