Modelling and analysis of a superconducting magnetic coupler used for cryogenic pump

It is difficult to achieve low heat leakage and leak-free rotary sealing for conventional small- and medium-sized cryogenic liquid pumps (CLPs). This is because the motor in a room-temperature environment is connected to the pump impeller (in a cryogenic environment) via a long transmission shaft. An axial flux-concentration superconducting magnetic coupler (AFCSMC) is proposed for CLP to eliminate the transmission shaft. Firstly, the structure and the operation mechanism of AFCSMC are described. Then, a 2D electromagnetic modelling method for AFCSMC is established based on the H-φ formulation and also validated experimentally in terms of the prediction on the levitation force and the guidance force. Thus, the 2D numerical simulations of AFCSMC are performed in an equivalent static system instead of the actual double rotor motion system in which the moving mesh is quite complicated. It is investigated that dependences of the transmission torque on the key electromagnetic structural parameters, such as permanent magnet arrangement, number of pole-pairs, ferromagnetic yoke, operating slip, and so on. The results indicate that the average transmitting torque is less affected by the operating slip, and AFCSMC can start asynchronously and operate in steady state with a synchronous speed. With the advantages of low loss, risk-free of desynchronising, and overload protection, the proposed AFCSMC can provide a competitive candidate for mechanical power transmission technologies in cryogenic engineering.