Influence of conical degree on the performance of radial and axial integrated auxiliary bearing for active magnetic bearing system

In this paper, a radial and axial integrated auxiliary bearing (RAIAB) device which can eliminate all radial and axial protective clearances after the rotor dropping is proposed to improve the reliability of the active magnetic bearing systems. In the proposed RAIAB, a strategy that the rotor end and the inner bushing are machined into conical surface is adopted so that the radial and axial clearances between the rotor and the inner bushing can be eliminated simultaneously when the inner bushing moves along the axial direction. In order to research the influence of the conical degree of the inner bushing on the performance of the RAIAB, the preliminary prototype experimental rig is developed and the cases of a 5 degree of freedom AMB rotor dropping on RAIABs at maximum speed of 30000 rpm are tested. The experimental results show that the RAIAB installed with a 30-conical degree inner bushing can successfully eliminate all protective clearances after the AMB rotor drops. However, the RAIAB installed with a 45-conical degree inner bushing is not able to eliminate clearance when the dropping speed of the rotor exceeds 18000 rpm.