Thermal Analysis of a Toroidal Field Model Magnet with HTS Wires (original) (raw)
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Reduction of the Hot Spot Temperature in HTS Coils
IEEE Transactions on Applied Superconductivity, 2014
A potential future Muon Collider requires high field solenoids (>30 T) for the final cooling stage; the Magnet Division at Brookhaven National Laboratory (BNL) is undertaking the task of demonstrating feasibility using High Temperature Superconductors (HTS). The aim is to construct an all HTS dual-coil system capable of delivering more than 20 T. Recently a new record for an all HTS solenoid has been established with a field of 15 T on-axis. In coil tests it was noticed that during a fast energy extraction the current in the solenoids decays faster in comparison to the expected exponential decay. This paper describes the effect and shows how it can be simulated using commercial finite element code. The faster current decay helps to lower the integral current density squared with time by about 10% and is therefore beneficial for quench protection.
A Study of Thermal Behaviour of HTS Devices at Alternating Current
International Journal of Electrical and Computer Engineering (IJECE), 2018
The paper presents a study on thermal behavior of a coil made of a high-temperature supercon-ducting tape representing operation of a superconducting device (for example, a transformer). Based on the results of a physical experiment, a mathematical model of superconducting coil operation under short circuit conditions at the load side was developed. Regimes of overheating by variable short circuit currents were investigated. In this case, short circuit current amplitudes exceeded a critical current of a superconductor, and coil parameters (e.g. an average nonlinearity parameter of a current-voltage characteristic, a superconductor length, and others) were varied. Permissible overheating for a coil with the possibility of its return into the superconducting state after emergency conditions in a dead-time period of automatic reclosing was considered. A criterion for return of a superconducting device into the superconducting state within a dead-time period of automatic reclosing has been obtained.
Thermal quench study in HTSC pancake coil
Cryogenics, 2000
In spite of rather high general stability of high temperature superconducting (HTSC) Bi-based magnets, catastrophic thermal quench (TQ) may appear in them under certain circumstances. It happens because of non-linearity of voltage±current characteristics in HTSC superconductors. Starting with small samples in our previous works, we continue to study the TQ with large samples. We prepared a highly instrumented HTSC pancake coil. It is wound using the Bi-2223-based tape. We attached many potential taps to the tape and installed in the winding 10 cryogenic thermocouples (TC) and two heaters. Quench development in the coil was measured under dierent temperatures, dierent magnetic ®elds and dierent cooling conditions. In this paper, the experimental details and the results obtained are presented. The results are discussed from the point of view of scaling theory for quenching in HTSC devices. Ó
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.
Parametric study for the cooling of high temperature superconductor (HTS) current leads
Cryogenics, 2013
The analysis of cooling of a binary HTS 20 kA current lead (CL) operating between 4.5 and 300 K has been carried out. Assuming that the HTS module is conduction-cooled, two cooling options for the copper heat exchanger (HEX) part of the CL have been considered, i.e. (1) cooling with a single flow of gaseous helium and (2) cooling with two flows of gaseous helium. The ideal refrigerator power required to cool the whole HTS CL has been calculated for both cooling scenarios and different values of input parameters and the thermodynamic optimization has been performed for both cooling options. The obtained results indicate that the cooling Option 2 cannot provide significant savings of the refrigerator power, as compared to the Option 1. However, it has been observed that at the same helium inlet temperature the temperature at the warm end of the HTS part, and the resulting number of HTS tapes, can be reduced in the Option 2 with respect to the Option 1.
—A conduction-cooled high-temperature supercon-ducting magnet using 2nd generation HTS wire, which has a room-temperature bore 102 mm in diameter, has been developed and tested up to 3 T with the operating temperature of 20 K. The magnet consists of 22 double pancake coils (DPCs) with an inner diameter of 140 mm and outer diameter of 182 mm. Twenty-two double pancake coils were tested separately at 77 K for checking the IV-curve. Selected DPCs were resistively connected by HTS tape (Splice joint), and an assembled magnet coil with the size of 182.5 mm diameter and 242 mm in height was conduction cooled by a two-stage Gifford–McMahon cryo-cooler to 20 K. Current, voltage, and field strength were measured as a function of time with various ramping up and down conditions. The resulting performance data of the assembled magnet agreed well with the expectation from FEM simulation. The aimed field homogeneity of 0.1% in 10 mm diameter sphere volume was proved when operating current was 141.6 A at 20 K with central magnetic field intensity of 2.9975 T by hall sensor. The magnetic flux density at center showed nonlinear dependence with ramping current within the range of 0.05 A/sec ∼ 0.15 A/sec because of charging delay. However, saturated magnetic flux density showed the same value of 2.9975 T regardless of ramping rate. Index Terms—Conduction cooled magnet, cryogen free, double pancake coil (DPC), quench, stability, 2nd generation (2G) HTS wire.
Thermal Analysis of a Cooling System for a High-Temperature Superconducting Magnet System
Various cooling systems for high-temperature superconducting (HTS) magnet applications were analyzed and discussed before. Among these systems, solid nitrogen (SN2) hybrid-type cooling system is one of a reliable, inexpensive, compact and stable one. The motivation of the study is to develop the thermal characteristic of hybrid-type cooling system for HTS magnet applications – it includes the design of an assembly of stacked second generation high temperature superconductor 2G HTS double pancake coils, each of which is wound without turn-to-turn insulation. Then, heat-transfer analysis of the 2G HTS magnet is carried out using 3D finite-element analysis (FEA) tool.
Effect of thermal contact between winding pack and casing on thermal behavior of SST1 TF coil
Fusion Engineering and Design, 2006
Active cooling of the casing, which houses the winding pack of the large size superconducting magnet used for magnetic confinement of plasma under a steady state configuration, has been one of the points for debate. Toroidal field (TF) coils of SST-1 consists of six double pancakes of Nb-Ti based cable-in-conduit conductor (CICC), duly impregnated and encased in a tight fit stainless steel casing. In order to validate the cooling configuration of the SST-1 TF magnet system, an experiment has been done on one of the full scale TF coil without having cooling channels for the casing. The experimental results show a distributed temperature profile on the casing ranging from the lowest temperature of 17 K to the highest temperature of 29 K. The data obtained has been analyzed on the basis of thermal contact and thermal resistance. The paper will describe the experimental setup, thermohydraulic behavior of the CICC in winding condition and the comparison of experimental results with an empirical analysis.
Parametric Analyses of JT-60SA TF Coils in the Cold Test Facility With SuperMagnet Code
IEEE Transactions on Applied Superconductivity, 2018
The toroidal field (TF) system of JT-60SA tokamak comprises 18 NbTi superconducting coils. In each TF coil, 6 cablein-conduit conductor (CICC) lengths are wound into 6 doublepancakes and carry a nominal current of 25.7 kA at a temperature of 4.7 K. Each coil is tested in the cold test facility (CEA Saclay), up to quench. A SuperMagnet (CryoSoft) model has been developed, each of the 12 pancakes being modeled with THEA and cryogenic circuit being modeled with FLOWER. The experiments showed that helium inlet temperature increases until quench triggering at about 7.5 K on C11 and C13, with quench starting on a lateral and on a central pancake, respectively. Each test has been simulated, applying (or not) a realistic heat load from casing to winding pack that was estimated from experimental measurements. A parametric analysis has been performed, considering realistic or null heat flux deposition, variation of friction factor (in fabrication quality range), and CICC critical current density (in strand J c performance range). This last parameter was found to have the largest impact on the localization of the first quenched pancake (central or lateral).