Dynamic resistance measurement in a four-tape YBCO stack with various applied field orientation

The dynamic resistance which occurs when a superconductor carrying DC current is exposed to alternating magnetic field plays an important role in HTS applications such as flux pumps and rotating machines. We report experimental results on dynamic resistance in a four-tape coated conductor stack when exposed to AC magnetic fields with different magnetic field angles (the angles between the magnetic field and normal vector component of the tape surface, θ) at 77 K. The conductors for the stack are 4-mm-wide SuperPower SC4050 wires. The field angle was varied from 0° to 120° at a resolution of 15° to study the field angle dependence of dynamic resistance on field angle as well as wire Ic (B, θ). We also varied the field frequency, the magnetic field amplitude, and the DC current level to study the dependence of dynamic resistance on these parameters. Finally, we compared the measured dynamic resistance results at perpendicular magnetic field with the analytical models for single wires. Our results show that the dynamic resistance of the stack was mainly, but not solely, determined by the perpendicular magnetic component. Ic (B, θ) influences dynamic resistance in the stack due to tilting of the crystal lattice of the superconductor layer with regard to buffer layers. © 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works

Dynamic Resistance Measurement of a Four-tape YBCO Stack in a Perpendicular Magnetic Field

Dynamic resistance occurs when HTS (high-temperature superconductor) coated conductors carry dc current under ac magnetic field. This dissipative effect can play a critical role in many HTS applications. Here, we report on dynamic resistance measurements of a four-tape YBCO stack comprising 4-mm-wide coated conductors, which experience an applied ac perpendicular magnetic field with an amplitude of up to 100 mT. Each tape within the stack carries the same dc current. The magnetic field amplitude, the frequency of the magnetic field, and the dc current magnitude are varied to investigate the influence of these parameters on the dynamic resistance. We find that the threshold field of the stack is significantly larger than that of a single tape when dc current is small, which we attribute to coherent shielding effects from circulating currents present in each wire in the stack. © 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works

Research data supporting "Origin of the DC output voltage from a high-Tc superconducting dynamo"

Research data supporting [Origin of the DC output voltage from a high-Tc superconducting dynamo]. Please see the README file for a description of the dataset

A Superconducting Induction Motor with a High Temperature Superconducting Armature: Electromagnetic Theory, Design and Analysis

Large electric superconducting machines are being sought to solve emissions challenges in aircraft and provide a solution to >12 MW wind turbine electricity generation. Superconducting motors with only high temperature superconducting (HTS) armatures can offer advantages of high reliability, high power density, and high efficiency compared with conventional superconducting motors. In this paper, a novel HTS squirrel-cage induction motor is proposed for high speed operation, which adopts the structure of HTS windings with a certain inclination angle in the stator slots. Due to the limitation of curvature radius of superconducting tapes, the pitch of HTS windings can be only set to 1 and adopt the short pitch arrangement structure, which such design details of the HTS motor would ensure the superconducting coils can undertake larger current and reduce AC losses. In order to keep the HTS windings in superconducting state and larger current density, a special fixed cryogenic cooling system below 70 K with the method of gas extraction and decompression, which is made of aramid fiber, has been fabricated and the whole structure of the stator is placed in liquid nitrogen. According to the motor control principles and electromagnetic field theory, the electrical performances of the novel designed stator-HTS motor, which driven by the variable-voltage variable-frequency (VVVF) inverter, are analyzed including the flux density distributions, the torque, the induced electromotive force, losses and efficiency by using the finite element method. Finally, the components of HTS squirrel-cage induction motor have been manufactured according to the designed parameters. Next step, the motor will be assembled and tested

Research data supporting "Modeling stator versus magnet width effects in high-Tc superconducting dynamos"

Research data supporting [Modelling and measurements of stator vs magnet width effects in high-Tc superconducting dynamos]. AMSC_Jc_B_theta_T.txt: J_c(B, theta) data used in the H-formulation model, calculated by normalising experimental I_c(B, theta) by the cross-section of the modelled wire. Data was measured at 35, 53 and 83 K in magnetic fields up to 0.7 T from a short sample of AMSC 46 mm wide superconducting wire. The four columns in the data file relate to temperature [units of kelvin], magnitude of magnetic field B [units of tesla], magnetic field angle [units of degrees] and I_c/w [units of A/cm]

Modelling of various rectifier flux pump topologies enabled by JcB switches

International audienceA Flux pump (FP) is a high current generating device for powering superconducting magnets. Based on their operating mechanism, they can be broadly classified into two types: dynamo FP and rectifier FP. In this paper we built the circuit models of various rectifier FP topologies, which uses DC field controlled HTS switches for the rectification purpose. The topologies are listed as: (i) half-wave retifier FP with a series resistance, (ii) half-wave rectifier FP with two switches, (iii) full- wave rectifier FP with four switches and (iv) full-wave rectifier FP with two switches. All these topologies are built within the MATLAB/Simscape platform using the predefined Ic(B) look up tables. The results show the flux pumping phenomena for various topologies using the input sinusoidal current controlled source. The modelling results from the half-wave rectifier FP model with two switches are verified against the experimental results. A feedback controlled switching methodology of the applied field switch for maximised operating efficiency is proposed for the first time in this paper. The maximum efficiency values achieved for various topologies are tabulated for comparison purpose. This models presented in this paper helps to understand the rectifier FP operating mechanism and also to optimise the FP design for the appropriate load characteristic

Modelling of various rectifier flux pump topologies enabled by JcB switches

International audienceA Flux pump (FP) is a high current generating device for powering superconducting magnets. Based on their operating mechanism, they can be broadly classified into two types: dynamo FP and rectifier FP. In this paper we built the circuit models of various rectifier FP topologies, which uses DC field controlled HTS switches for the rectification purpose. The topologies are listed as: (i) half-wave retifier FP with a series resistance, (ii) half-wave rectifier FP with two switches, (iii) full- wave rectifier FP with four switches and (iv) full-wave rectifier FP with two switches. All these topologies are built within the MATLAB/Simscape platform using the predefined Ic(B) look up tables. The results show the flux pumping phenomena for various topologies using the input sinusoidal current controlled source. The modelling results from the half-wave rectifier FP model with two switches are verified against the experimental results. A feedback controlled switching methodology of the applied field switch for maximised operating efficiency is proposed for the first time in this paper. The maximum efficiency values achieved for various topologies are tabulated for comparison purpose. This models presented in this paper helps to understand the rectifier FP operating mechanism and also to optimise the FP design for the appropriate load characteristic

AC Loss Simulation in HTS Armature Windings of A 100 kW All-HTS Motor

International audienceAn all-HTS motor is a promising device that can provide more compact size and higher performance than conventional motors. However, high AC loss in the HTS armature windings requires large cryogenic system which makes all-HTS motors impractical. This work numerically studied AC loss behaviours of the HTS armature windings in a 100 kW, 1500 rpm HTS motor. The model is based on COMSOL Multiphysics and T-A formulation. In order to investigate the real time electromagnetic behaviours, the moving mesh and rotating machinery interface are applied in this model. Preliminary results on magnetic flux distribution in the whole motor, current density in the HTS armature windings as well the AC loss are presented

AC Loss Simulation in HTS Armature Windings of A 100 kW All-HTS Motor

International audienceAn all-HTS motor is a promising device that can provide more compact size and higher performance than conventional motors. However, high AC loss in the HTS armature windings requires large cryogenic system which makes all-HTS motors impractical. This work numerically studied AC loss behaviours of the HTS armature windings in a 100 kW, 1500 rpm HTS motor. The model is based on COMSOL Multiphysics and T-A formulation. In order to investigate the real time electromagnetic behaviours, the moving mesh and rotating machinery interface are applied in this model. Preliminary results on magnetic flux distribution in the whole motor, current density in the HTS armature windings as well the AC loss are presented