Guidance Force and Its Hysteresis of YBCO Bulks Under a Low-Pressure Environment

High temperature superconducting (HTS) maglev train running in the evacuated tube is a new kind of transportation with great potential. The HTS bulks are core component of the HTS maglev train, and its guidance performance is crucial to the ability of curve-passing. Therefore, it is necessary to study the guidance force of YBCO bulks under a low-pressure environment. Based on the test system of magnetic levitation characteristics under low-pressure environments, the super-cooling state of liquid nitrogen is realized by the method of evacuation. The guidance force of YBCO bulks moving laterally above a Halbach permanent magnetic guideway was measured under different pressure values (100, 60, 40, 20 kPa). Results show that decreasing pressure is beneficial to improve the guidance performance of YBCO bulks. When the field cooling height (FCH) is under 35 mm, the guidance force increases with the decrease of the pressure. However, when the FCH is more than 35 mm, the guidance force decreases with the decrease of the pressure. Furthermore, decreasing FCH and pressure value can decrease hysteresis of guidance force and enhance the lateral stability of the HTS maglev system.