New Three-Pole Combined Radial-Axial Magnetic Bearing for Industrial Bearingless Motor Systems

This article investigates combined radial-axial magneticbearing (CRAMB) technology as an enabling component for shafted bearingless motor systems. The unique requirements of high-speed bearingless motors designed for significant power levels are used to guide a literature review on CRAMB designs. Fundamental bearing topology aspects are identified and compared. Based on the outcome of this review, a new CRAMB topology is proposed and developed to meet the needs of a bearingless motor. Key features of the proposed design include a three-pole radial force stage (driven by a three-phase motor drive) and utilization of an optimal bias flux that improves radial force density by approximately 15% (improved rotor dynamics). A full design procedure for the new bearing topology is developed and it is shown that compared to a conventional four-pole side-by-side CRAMB, this topology decreases the bearing shaft length and requires two fewer power electronic switches (6 instead of 8). The new bearing is validated via finite-element analysis and experimental test results.

Automated summary

This study investigates the use of combined radial-axial magnetic bearing technology as a key component for shafted bearingless motor systems, proposing a new CRAMB topology to meet the needs of high-power bearingless motors. The new design features higher radial force density and a more compact structure compared to conventional designs.