Experimental investigation on stiffness and damping characteristics of hybrid foil magnetic bearings

Abstract

Hybrid Foil Magnetic Bearings (HFMBs) are a promising bearing technology for high-speed, oil-free turbomachinery that structurally embeds a gas foil bearing (GFB) into the inner diameter of an active magnetic bearing (AMB). The flexible foil structure provides sufficient support stiffness for the rotor, while closed-loop control allows real-time adjustment of the dynamic performance of the bearing. In this paper, the static and dynamic performance of the HFMB is measured experimentally. The effect of the control gain on the static and dynamic performance of the HFMB is highlighted. The proportional gain increases the stiffness but weakens the stability of the system, while the differential gain increases the damping but unexpectedly increases the stiffness. The static and dynamic performance of the HFMB is compared with that of the GFB. At low excitation frequencies, the stability of the GFB is higher than that of the HFMB, while as the excitation frequency is increased, the stability of the HFMB exceeds that of the GFB.