Authors:
Xiaobao Shi;Qingyun Mao;Bo Zhang;Jun Jiang;Linjie Li;Lifeng Zhao;Yong Zhang;Yong Zhao;
Pages: 1 - 5 Abstract: The effects of temperature on the dynamic characteristics of a high-Tc superconductor (HTS) and permanent magnet (PM) system at different field cooled (FC) gaps and different masses are studied theoretically and experimentally. Results indicate that the resonant frequency of the HTS–PM system decreases with increasing FC gap or mass at different temperatures. Although decreasing temperature augments stiffness of the interaction force between the HTS and the PM. The effect of decreasing temperature on stiffness and resonance frequency is more significant at a smaller FC gap. It means that the enhancement of lowering temperature on stiffness and resonant frequency also depends on the magnetic field gradient. PubDate:
Jan. 2022
Issue No:Vol. 32, No. 1 (2022)

Authors:
Jing Shi;Wangwang Yang;Zhaofang Song;Xiao Zhou;Meng Liao;Zexu Chen;Zitong Zhang;Dengquan Lin;
Pages: 1 - 11 Abstract: Aiming at the problem of high-frequency pulsewidth modulation pulse voltage suffered by superconducting magnetic energy storage (SMES) magnets and the uneven distribution of voltage in the windings of the magnet, this article analyzes the influence of SMES magnet parameters on its voltage distribution characteristic. Taking solenoid magnet and toroidal magnet as research objects, the key parameters are selected to analyze the voltage distribution of different magnet schemes, and the influence rules are deduced. Then, an optimal design of SMES magnet considering voltage distribution characteristic is proposed. The influence rules can be set as the weight of key parameters in the electromagnetic optimization design of the magnet. Finally, to evaluate the effectiveness of the proposed design method, a 3.8 MJ SMES magnet design considering voltage distribution characteristic is carried out. PubDate:
Jan. 2022
Issue No:Vol. 32, No. 1 (2022)

Authors:
Natsumi Endo;Yoh Nagasaki;Daisuke Miyagi;Makoto Tsuda;
Pages: 1 - 6 Abstract: We have investigated the effectiveness of the insertion of a low thermal conductive layer (LTCL) in a triaxial high temperature superconducting (HTS) cable to realize a long-length triaxial HTS cable. This article analyzed the relationship among intrusion heat from outside of the cable, ac loss, temperature distribution, and the maximum temperature within a triaxial HTS cable with the LTCL to clarify the suitable insertion position and thickness of the LTCL for a long-length triaxial HTS cable. Analysis results showed that inserting the LTCL inside the HTS layers was effective for the long-length triaxial HTS cable. In addition, there was a tradeoff relationship between the effects of suppressing the thermal conduction from the outer refrigerant to the inner refrigerant and increasing the intrusion heat from outside of the cable by inserting the LTCL. The suitable thickness of the LTCL can be obtained by considering this tradeoff relationship. PubDate:
Jan. 2022
Issue No:Vol. 32, No. 1 (2022)

Authors:
Jakub Glowacki;Yueming Sun;James G. Storey;Taotao Huang;Rodney Badcock;Zhenan Jiang;
Pages: 1 - 8 Abstract: AC homopolar motors with high-temperature superconductors (HTSs) are considered to be a promising technology for high-power applications. With superconducting components being placed exclusively in nonrotating parts, a motor can reach high rotational speeds. However, the dynamic behavior of the system creates a nonnegligible magnetic ripple field, which generates heat and makes thermal management of the cryogenic system more challenging. In this article, we present a case study for the thermal behavior of a conduction-cooled high-temperature superconducting field coil assembly in a 500-kW asynchronous homopolar motor. The analysis focuses on the investigation of the magnetic ripple field and its impact on heat generation due to ac loss in the HTS field coil and eddy current loss in copper parts present in the assembly. Using electromagnetic and thermal finite-element models, we construct a detailed description of the thermal bus design, which considers different cooling scenarios and sizing of the conductive elements. Depending on the geometry of the thermal bus, we observe heat loads from ac losses of up to 0.4 W and eddy current losses in the copper elements of up to 1 W. These heat loads translate to temperature increases as high as 10 K. Techniques to reduce the temperature rise based on thermal bus redesign are presented, along with recommendations for the most promising cooling scenarios and optimal thermal bus geometry. PubDate:
Jan. 2022
Issue No:Vol. 32, No. 1 (2022)

Authors:
Anabela G. Pronto;Filipe Vale;Nuno Vilhena;João Murta-Pina;
Pages: 1 - 5 Abstract: In transmission and distribution grids, electrical currents in rated conditions can reach hundreds of amps. Under fault conditions, these currents can reach ten times or more their rated value. In power devices, particularly in superconducting fault current limiters (SFCLs), this current rise leads to the development of electromechanical forces that can damage the superconducting tape, so should be properly analyzed, for the sake of equipment integrity. Additionally, when asymmetric faults occur in the grid, the desired circumstance is that a fault in one phase does not affect the other ones, to minimize damages and disturbances in the grid and protection devices. In this article, core- and a shell-type inductive SFCLs are tested under several fault conditions. The main objectives are to measure and analyze the electromechanical forces developed in each superconducting winding, to evaluate their integrity after faults, and to compare the performance of both types of limiters under the same fault conditions. Electromechanical forces measurements in the three phases are made simultaneously, using a device based on strain gauges, calibrated to operate at 77 K. This article contributes to evaluating the robustness and best geometry of this inductive limiter of transformer type. PubDate:
Jan. 2022
Issue No:Vol. 32, No. 1 (2022)