Flux measurement and conditioning system for heteropolar active magnetic bearing using Kapton-foil Hall sensors

This paper addresses the problem of measuring the electromagnetic flux in the air gap of the active magnetic bearing (AMB) without mechanical structure modifications. The designed and fabricated flux measurement and conditioning system based on the ultra-thin flexible Kapton-foil Hall sensors (developed by IFW Dresden Institute for Integrative Nanosciences) and signal amplifiers are presented. The flexible sensors are directly mounted on the curved surfaces of stator poles of the AMB and measure flux density in the AMB air gap. Then, the measurement itself and the conditioning system are verified in different measuring conditions of the heteropolar radial AMB with the air gap width of 0.4 mm. The measurement results were used in identifying crucial rotor flux-AMB system parameters. The proposed direct flux measurement system is successfully verified in the designed test rig in the presence of rotor position disturbances or coil current oscillation. The advantages and drawbacks of the presented measurement setup are discussed.