Suspension and guidance performance of a new superconducting EDS system using the 8-shaped ground coils with non-equal turns

The electrodynamic suspension (EDS) system composed of superconducting magnets (SCM) and 8-shaped ground coils (GC) has the characteristics of large suspension gap, high lift-to-drag ratio and self-stabilization, etc. It has been applied and developed in high-speed maglev transportation and electromagnetic launch. When the EDS system runs at low speed, the suspension force is insufficient, and the mechanical assistant equipment is needed to provide the supporting force. The minimum lifting speed of the system is generally higher than 100km/h. In order to reduce the lifting speed, this paper proposes a non-equal turns ground coil (NET-GC) scheme in which the number of the upper loop (u-loop) turns of the 8-shaped ground coil is less than that of the lower loop (l-loop) without changing the structure and parameters of SCM. This scheme theoretically increases the magnetic flux difference between the upper and lower loops, which can improve the suspensibility of the EDS system. Subsequently, the three-dimensional magnetic force numerical calculation model of superconducting EDS system is established. The change of SCM suspension force, guiding force and drag force with the turns difference coefficient (k) of NET-GC scheme is obtained, and the suggested value of k is given. Finally, taking the value of k as 0,3/24 and 5/24 as examples, the magnetic characteristics and minimum lifting speed of EDS system under various working conditions are analyzed. The calculation results show that compared with the S-GC scheme, NET-GC improves the suspension and guidance capability. Under the same load conditions, the minimum lifting speed of the EDS system is significantly reduced, and the amount of ground coil material is saved. However, the NET-GC scheme also causes the magnetic force high frequency harmonic amplitude and the mean value of drag force to increase, but it is still far less than the aerodynamic drag force of high-speed operation.