Metal-insulation (MI) REBCO high-temperature superconducting (HTS) magnet has the advantages of short charging delay, low contact losses, and self-protection abilities, which shows important application prospects in many fields. Recently, Institute of Electrical Engineering, Chinese Academy of Sciences developed a prototype on-board MI HTS coil used for electrodynamic suspension (EDS) system working with an acceleration of beyond 8 g. To design a reliable engineering on-board magnet, specific I_c angle dependence data of short sample under different fields were fully considered to estimate the operating margin and losses accurately of the on-board magnet. A semi-analytical method, combination of the dynamic circuit method and finite element method, was used to analyze the dynamic electromagnetic force distribution inside the on-board magnet under motion state, in which the effect of the propulsion coils and the figure-eight-shaped coils were taken into considerations. Finally, a full-size MI double pancake racetrack coil was fabricated and tested in a liquid nitrogen bath. The test results meet the design requirements and verify the feasibility of the design, which provides an important reference for the experiment of on-board EDS with high acceleration in the future.

The technology of superconducting electrodynamic suspension (EDS), which has the characteristics of strong suspension ability and good self-stability, is a candidate technology for ultra-high-speed maglev transportation and electromagnetic launch systems in the future. This paper focuses on the modeling method of null-flux coil-type superconducting EDS for narrow gauge based on dynamic circuit theory (DCT) and its characteristic analysis. Methods of self-inductance of coils and mutual inductance between coils are introduced, which have characteristics of rapidity, accuracy and simplicity. On this basis, the modeling methods of null-flux coil-type EDS systems including cross-connected type and non-cross-connected type are proposed, which can be applied to narrow-gauge situations. Then, two program implementation methods based on spatial uniform discretization and time uniform discretization are discussed. To verify the effectiveness of the proposed analytical model, the finite element method (FEM) and the measured data in the Yamanashi line are adopted. Using the program based on spatial uniform discretization, the effects of velocity, heave, sway, and track gauge on the steady-state electromagnetic force characteristics of coil-type EDS systems are studied. Using the program based on time uniform discretization, the suspension process and vibration characteristics of the EDS system are preliminarily analyzed. The established analytical model can provide guidance for the design of EDS tracks.

In this paper, the factors affecting the evaluation of the equivalent contact resistance of the magnet were investigated by sudden discharge tests in a large-bore conduction-cooled metal-as-insulation (MI) high-temperature superconducting (HTS) magnet with an inner diameter exceeding 450 mm and consisting of ninety double pancake coils. It was found that the evaluation results of the contact resistance of the magnet are influenced by the current, temperature, measurement position, and evaluation method. Subsequently, a power law relationship was used to describe the relationship of contact resistance with current and temperature, and the relationship of contact resistance with current showed an opposite trend to that expected, while the relationship with temperature was as expected. We compared the experimental results of other teams to try to provide a reasonable explanation for the above phenomenon. Additionally, we found a significant difference between the delay of the central and end magnetic fields and a difference in the evaluation results between the method of using the field to decay to 1/e of the initial value and the curve-fitting method. We analyze the reasons for these phenomena and give our explanations. Finally, based on our experimental results, a measurement method for the equivalent contact resistance of NI/MI HTS magnets was summarized to improve the evaluation accuracy. This paper is both the first systematic experimental study on the contact resistance of a large-scale object such as MI HTS magnets and a review of previous studies. The findings are hoped to provide guidance for evaluating equivalent contact resistance for NI/MI HTS magnets in future engineering applications.

Superconducting dynamic synchronous condensers (SDSCs) exhibit significant potential for replacing traditional dynamic synchronous condensers (DSCs) due to their powerful reactive power output capability and low thermal losses, which are attributed to their large short-circuit capacity, high air-gap magnetic density, and low synchronous reactance. This study comprehensively reviews the development trajectory and current research status of SDSC, both domestically and internationally, and conducts an in-depth analysis of their advantages. Based on this, this paper highlights three typical cases of SDSC and summarizes the key technologies of SDSC from the perspectives of the excitation winding, stator structure, rotor magnet, and cooling system. Finally, it proposes that cooling and insulation technology, quench issues of AC windings under magnetic fields, and torque tube transmission technology will be the key technical challenges for future research and resolution in SDSC.