Gyro-effect and Earnshaw's Theorem Stable and Unstable Equilibrium for Rotary and Stationary Permanent Magnetic Levitators

摘要

Earnshaw's theorem(1839) stated that no stationary object made of magnets in a fixed configuration can be held in stable equilibrium by any combination of static magnetic or gravitational forces. What happens by a moving body like a rotating passive magnetic levitator? Nobody has given an answer until now. The author applied a self-made passive magnetic bearing to radial pump and turbine machine, and found that if the rotating speed could be higher than a critical value, 3250rpm by a pump and 1800rpm by a turbine, the rotors would be disaffiliated from stators and keep the rotation stable. It seems that the fast rotating levitator has a so-called 'Gyro-effect' which makes the passive maglev rotator stable. These results have extended Earnshaw's theorem from static to dynamic equilibrium: In stationary state or by a speed lower than critical value, the permanent maglev rotator cannot keep rotation stable; if the rotating speed is higher than critical speed, the permanent maglev rotator will have Gyro-effect which stabilizes unstable levitator.