Modeling and Electrical Measurement of Transport AC Loss in HTS-Based Superconducting Coils for Electric Machines (original) (raw)
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IEEE Transactions on Applied Superconductivity, 2017
In this paper, the transport AC losses in a triangular, epoxy-impregnated high temperature superconducting (HTS) coil made from YBCO coated conductor, intended for use in a prototype axial flux HTS electric machine, are measured using two different electrical techniques at 77 K. The first set of AC loss measurements of the coil are carried out at the University of Cambridge using a technique based on a lock-in amplifier. The coil is then measured at the Center for Advanced Power Systems (CAPS), Florida State University, using a technique based on a high accuracy data acquisition (DAQ) measurement system. The two different methods show consistent results, validating the accuracy of these two techniques for transport AC loss measurements of superconducting coils. Multiple voltage taps are utilized within the coil to study the details and distribution of the AC loss in different sections of the coil. Losses are also measured with a flux diverter made of ferromagnetic material to analyze its effect on the AC losses. Index Terms-AC loss, critical current density (superconductivity), high-temperature superconductors, superconducting coils, transport ac loss.
AC Loss Modeling in Superconducting Coils and Motors With Parallel Tapes as Conductor
IEEE Transactions on Applied Superconductivity, 2019
Many superconducting power applications contain REBa2Cu3O7−x (or REBCO) coils, where RE stands for "rare earth". Superconducting motors are very interesting for mobile applications like aviation, thanks to their high power per unit weight. In order to reduce the inductance, multi-tape conductors are often used in windings but parallel tapes present coupling AC loss. In this article, we analyze the AC loss of single coils and a full stator of a motor made of windings of parallel tapes, taking several coupling situations into account. Our computer modeling method combines self-programmed and commercial finite-element methods to calculate the current density and AC loss. We found that isolating the tapes along the length provides almost the same AC loss reduction as that obtained by full transposition. This reveals that there are still many unexploited strategies to reduce the AC loss in multi-tape conductors.
Measurement of AC Losses in a Racetrack Superconducting Coil Made from YBCO Coated Conductor
Physics Procedia, 2012
We present the results of transport measurements of AC losses in a racetrack shaped superconducting coil made from coated conductor tape. The outer dimensions of the coil are approximately 24 cm × 12 cm and it has 57 turns. The coil is impregnated with epoxy resin and fiberglass tape is used to insulate the individual turns and to improve the mechanical properties of the epoxy when exposed to thermal cycling. The coil is manufactured as a part of the field winding of a small synchronous generator; therefore stainless steel frames are installed on the inner and outer side of the winding to reinforce it. The AC loss is measured versus the transport current I a with the coil immersed in liquid nitrogen. Measurements at frequencies 21 Hz, 36 Hz and 72 Hz are compared. The AC losses follow I 2 a dependence at low current amplitudes and I 3 a at high amplitudes. After cutting the inner steel frame the low amplitude losses are decreased, their frequency dependence is reduced but their dependence on the current remains unchanged.
Applied Physics …, 2012
A two-axis goniometer for low-temperature nuclear magnetic resonance measurements on single crystals Rev. Sci. Instrum. 83, 093901 (2012) Study of second generation, high-temperature superconducting coils: Determination of critical current J. Appl. Phys. 111, 083902 Manufacturing of a superconducting magnet system for 28 GHz electron cyclotron resonance ion source at KBSI Rev. Sci. Instrum. 83, 02A347 Characteristic and magnetic field analysis of a high temperature superconductor axial-flux coreless induction maglev motor J. Appl. Phys. 111, 07E707 Design and investigations of the superconducting magnet system for the multipurpose superconducting electron cyclotron resonance ion source Rev. Sci. Instrum. 83, 02A319 Additional information on Appl. Phys. Lett.
AC Loss Analysis of HTS Pancake Coil of Coated Superconductors with Ferromagnetic Substrate
The influence of the ferromagnetic substrate on the AC loss of an HTS coil is extensively investigated by the finite element method. The model assumes the utilization of the coated conductors with a ferromagnetic substrate to construct the coil windings consisting of several turns. The calculations for both the strong and weak ferromagnetic layers were accomplished. The calculation is presented how to change the current distribution inside a superconducting region by the ferromagnetic layer.
AC loss in a high-temperature superconducting coil
Physica C: Superconductivity, 1998
In a typical superconducting coil made of BSCCOrAg tape, both amplitude and direction of the magnetic field determine the critical current, resistive voltage and AC loss. The distribution of the magnetic field along and across the superconducting tape in a coil is rather complex. This gives rise to the question: how accurate can one predict the critical current, V-I characteristic and AC loss of the AC coil from results of short sample measurements? To answer this question, we have measured and compared the characteristics of a short sample and a small coil employing ; 14 m of the same tape at 77 K. The comparison is performed as follows. First, a short sample is characterised with regard to the field dependence of the critical current, V-I characteristic and the AC loss. Second, the distribution of the magnetic field along the tape in a coil is accurately calculated. From the data, the voltage along the tape and the loss of the tape in the coil are found. Finally, the resistive voltage and the AC loss of the complete coil are calculated and compared to measured AC losses in the frequency range of 0 to 160 Hz, typical for power applications.
HTS Superconducting Coils for Applications in Electrical Engineering
2016
The HTS superconducting coils that are components of the rotating electrical machines made in ICPE-CA, work at the liquid nitrogen temperature (77K). They are made of ceramic material, YBCO type, which has a critical current of 130A (SuperPower) and 100A respectively (AMSC). There are analyzed two different types of coil for two prototypes of electrical machines: an electric motor (P = 4 kW) and an electric generator (P = 4.5 kW). They were made from HTS tape, in the form of simple and double racetrack pancake. Within the paper the design parameters of these HTS coils are examined. Also, the generated magnetic field, the field numerical simulation and the optimal functioning conditions are analyzed.
High temperature superconducting (HTS) synchronous motors can offer significant weight and size reductions, as well as improved efficiency, over conventional copper-wound machines due to the higher current density of high temperature superconducting (HTS) materials. In order to optimise the design parameters and performance of such a machine, this paper proposes a basic physical model of an air-cored HTS synchronous motor with a copper armature winding and HTS field winding. An analytical method for the field analysis in the synchronous motor is then presented, followed by a numerical finite element analysis (FEA) model to verify the analytical solution. The model is utilised to study the influence of the geometry of the HTS coils on the magnetic field at the armature winding, and geometrical parameter optimisation is carried out using this theoretical model to obtain a more sinusoidal magnetic field at the armature, which has a major influence on the performance of the motor.