Fabrication and test of an axial-field HTS rotating machine with integrated magnetic coupling

Abstract

High Temperature Superconducting (HTS) electrical machines have high torque density with a very high efficiency. Torque tubes are usually used to transmit the torque from the cold to the warm environment which results in thermal losses and mechanical problems. To overcome these difficulties, we propose to transmit the torque of the HTS machine through an integrated HTS magnetic coupling. A prototype has been constructed and tested showing the effectiveness of the proposed solution. The machine and the coupling share the same HTS rotor while the torque produced by the machine is transmitted to the load via a permanent magnets rotor. This solution allows the reduction of the thermal losses and a natural protection against overload during fault. The electromagnetic design is carried out using 3D finite elements. The HTS material electrical behavior is described using a power law so it was possible to determine the operating current of the HTS coils of the device. Many test results such as curves of the HTS coils, static torques, back-EMF and on-load characteristics are presented and checked by the FE computations.

Thermal conductivity and stability of commercial MgB2conductors

“…This difference is due to the use of SS instead of nickel in sample B, since this leads to a larger c Av . NZPV L values obtained in this work are of the same order of magnitude than those measured experimentally or determined numerically for other MgB 2 technical conductors[26][27][28][29]31].Our simultaneous study of the longitudinal and transverse thermal conductivities has given us the possibility…”

“…) have been measured in MgB 2 samples with much larger Cu/non-Cu ratios with respect to the tapes investigated in this work [29]. However, it is worth noting that MQE of the order of 10 mJ is at least two order of magnitudes higher than typical values of low-T c superconductors [8,26].…”

A quench detection method for parallel co-wound HTS coils based on current redistribution

“…In order to prove the accuracy of the analysis results, experimental results are compared with the theoretical derivation proposed in section 2 at 3.0 A s −1 rate charging to 50 A operation, shown in figure 10. In the theoretical derivation, the value of L 1 = 272.12 µH, L 2 = 273.17 µH and M = 271.29 µH are given by finite element analysis, and the quench resistance is given by cubic polynomial fitting of current and voltage from data of the quench experiment, and the fitting result is given by equation (17). The joint resistances between parallel windings and metallic current joints is specified as 1200 nΩ and the solder resistances is specified as 100 nΩ respectively, whereas R a and R b are both 48 nΩ.…”

“…High-temperature superconducting (HTS) coated conductors (CCs), which have high engineering current densities, critical magnetic fields, operating temperatures and mechanical properties, have been widely used for superconducting magnet applications [1][2][3]. HTS magnets wound from CCs coils have been developed for various applications, such as high field magnets [4][5][6][7][8][9], nuclear fusion [10,11], nuclear magnetic resonance (NMR/MRI) [12][13][14][15][16], HTS rotating machines [17][18][19][20], * Authors to whom any correspondence should be addressed.…”

Superconducting cryo-magnets processed by spark plasma sintering and texturing

“…Since the discovery of high temperature superconductivity (HTS) [1], intensive research has been devoted to discovering new materials [2][3][4][5][6][7][8][9], in order to improve the superconducting properties [10][11][12][13][14][15][16] and/or develop different devices such as permanent magnets, motors, and flywheel energy storage for potential applications [17][18][19][20][21][22][23][24].…”