Basic study on active magnetic bearing working in liquid nitrogen and its application to cryogenic pump

This paper discusses an active magnetic bearing (AMB) able to work in liquid nitrogen, which is composed of a stator with four electromagnets (EMs), a rotor, displacement sensors, a permanent magnet (PM) motor, etc. In this paper, two types of AMBs are discussed. One AMB is made to study basic characteristics of the AMB in liquid nitrogen. The other one is made to study basic characteristics of a pump able to work in liquid nitrogen. The rotor is levitated in the center of the stator with a pivot bearing at the rotor bottom. The pump performances using the AMB are studied by measuring the displacement of spinning rotor at extremely low temperature 77 K.