Electromagnetic Bearing

Abstract

A shaft is supported by means of a laminated rotor which is magnetically suspended inside a four pole laminated stator. The diameter of the rotor is 1¾ in. and the radial clearance is 0.002 in. The position of the shaft is sensed with the aid of four quadrant electrodes which surround the shaft with a small radial clearance. Each electrode provides part of the tuning capacity of an rf tuned circuit which is tuned to one side of its resonance peak with respect to an rf generator. The rf signal is detected and amplified to provide the control current in the corresponding winding on the stator. The bearing was found to run smoothly up to 23 000 rpm. With further development, a reliable and useful bearing should result. The use of electromagnetic bearings would appear to be justified in special applications where conventional bearings cannot be employed. They would appear to be useful at cryogenic temperatures, in vacuums, and in applications where contamination with lubricants must be avoided. Since there is no wear the life should be indefinite.