A 100 percent passive magnetic bearing flywheel rig was designed, constructed and tested without using any active control components. The suspension of the rotor was provided by two sets of radial permanent magnetic bearings operating in the repulsive mode. The axial support was provided by jewel bearings on both ends of the rotor. The rig was successfully operated to speeds of 5500 rpm, which was above the first critical speed of 3336 rpm. It was not continued beyond this point because of the excessive noise generated by the air impeller and because of inadequate containment. Radial and axial stiffnesses of the permanent magnetic bearings were experimentally measured and then compared to finite element results. The natural damping of the rotor was measured and a damping coefficient was calculated.
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