Active magnetic bearing

An active magnetic bearing supports a rotating shaft on a controlled magnetic field instead of an oil film or rolling elements, so there is no mechanical contact and no lubricant. Position sensors feed a digital controller that drives radial and axial electromagnets thousands of times per second to hold the rotor centered in its gap, typically 0.5 to 1 mm. Marine use is mainly in high-speed turbomachinery: turbo-compressors, some turbo-expanders, and certain high-speed motors. Benefits are zero friction loss, no oil contamination, and active rotordynamic control. A backup touchdown bearing catches the rotor on power loss.