Papers by Keyword: HTS

Abstract: The AC loss calculation is crucial for the thermal analysis of the High Temperature Superconducting (HTS) magnet. Generally, the critical state model is used to calculate the AC loss value of the HTS conductor with Finite Element Method (FEM). The mesh of the model have a large impact both on the convergence and the accuracy in calculation processes. In this paper, we investigate the effect of different meshes on the AC loss calculation of HTS conductors using a second generation tape model. Both triangular and quadrangle element with fix number of elements and predefined distribution type meshes have been used. The results illustrates that quadrangle with geometric sequence is the best choice when calculating the AC loss in HTS tape.

Abstract: This paper presents the design of a wide-stopband HTS bandpass filter (BPF). The 9-pole wide-stopband BPF has a center frequency 2.21GHz and bandwidth 100 MHz. Based on the step impedance resonator,this filter increase the harmonic frequency to more than 3 times of fundamental frequency. Optimization simulation results shows that insertion loss is less than 0.3 dB in the passband,and stopband suppression is greater than 80 dB within 0~f0-BW and greater than 60 db within the f0 + BW ~ 3 f0. Within the passband, dB (S (2, 1)) < -20. This design not only achieved a good wide stopband and solved the interference problem but also had a simple structure which is easy to implement.

Abstract: Due to the high current density in 77K, the high temperature superconducting facilities are expected to improve the efficient in power transmission. Superconducting facilities electromagnetic design is highly dependent on the characteristic of the superconducting tape. As a result, the comparison of the effect of different tape in electromagnetic design should be studied. In this paper, several facilities model are used as example to analyze the effect of different tape utilization. The result shows in different application conditions, or, specific benefits are considered, there is a specific tape will be the best choice.

Abstract: In high temperature superconducting (HTS) magnet design, it well known that the critical current (I_c) is sensitive to the direction of the local magnetic field. The perpendicular magnetic field component to the face of tape have a larger effect on the I_c of a HTS tape than the parallel component. Thus in HTS magnet design, the magnetic field distribution is the first considering factor. This work presents a HTS magnet design using genetic algorithm to obtain the object. When the length of the tape is certain, the results show that the process gives the optimal number of the double pancake and the inner radius of the magnet.

Abstract: Chip to Chip bonding technology using Cu bumps with solder capping layer has been widely investigated for 3D chip stacking applications. We studied the reliability of the Cu joints. Cu bumps capped with Sn-Ag solder layer were joined to bare Cu pads or Au/Ni electroplated Cu pads at 300°C for 10 sec after dispensing non-conductive paste (NCP). After joining, there were no failed joints and the contact resistance of the joints was very low in all specimens. High temperature storage (HTS) test (120°C, up to 2000 hrs) results demonstrated that the reliability was good in all specimens, while thermal cycling test (-55°C /+125°C, up to 2500 cycles) results showed that the contact resistance of the joints increased quickly after 2000 cycles which was attributed the crack formation in the joint interfaces.

Abstract: Superconducting YBa2Cu3O7-δ
(YBCO) films were grown on MgO single crystalline substrates using a BaZrO3 (BZO) buffer layer deposited by a pulsed laser deposition (PLD). Deposition condition has been optimized to obtain good epitaxial BZO film followed by deposition of YBCO superconducting films. The crystallinity and microstructure of epitaxial YBCO/ BZO/ MgO (00l) films were investigated by a two-dimensional x-ray diffraction and a field emission scanning electron microscope. The in-plane (φ-scan) measurements for the BZO films (200 ~ 500 nm thick) grown on MgO substrates revealed a narrow full width half maximum (0φ = 2o). The XRD results exhibited that YBCO films with a BZO buffer layer were well oriented in the [00l] direction perpendicular to the substrate surface. The BZO films also showed homogeneous and dense surface morphologies. By the deposition of a subsequent BZO buffer layer, YBCO was grown epitaxially on MgO with results showing a critical current density (Jc) of ~ 3.3 × 106 A/cm2 and a critical temperature (Tc) of 86 K.

Abstract: Up to now most of the efforts for developing HTS technology have been directed to devices for grid applications. However, HTS synchronous machines as motors and generators become more and more interesting within the world-wide development programs. Replacing the copper winding of the rotor by an HTS one and introducing an iron-less aircore stator winding the very compact HTS machine has less than half the weight and volume, higher efficiency and an excellent operational behavior when compared to the conventional devices. These features make HTS rotating machines very attractive for e.g. ship drives and industrial applications for the processing industry and power generation in power plants and wind parks. World-wide, HTS machines have already demonstrated their advantages and technical feasibility. The prototypes are ranging from the 5 MW low-speed high-torque propulsion motor to the high-speed 3600 rpm 4 MVA HTS generator. Feasibility studies clearly show the financial benefits when introducing high-efficient HTS wire based rotors into a large scale power generator systems. At present, most of the industry driven activities take place in the United States, Germany, Japan and Korea and are mainly directed towards applications aboard ships. Further potential applications as well as the technical and economic benefits will be discussed.