Development of binary superconducting current leads with a gas cooled normal part (original) (raw)
Related papers
Design of superconducting current leads
Cryogenics, 1994
The thermal behaviour of superconducting current leads operating between 4.2 and 293 K has been studied. For operating current densities above 10 000A cm -2, textured Bi-2223/Ag tapes are an alternative to Bi-2212 bulk material. Results for these two cases will be compared. The room temperature refrigerator power required to cool a superconducting current lead has been calculated for different cooling concepts, taking into consideration the normal conducting copper part. Use of high Tc superconductors has the potential to reduce the required room temperature refrigerator power to onefifth of that consumed by a conventional current lead. The effects of complete coolant loss have been simulated numerically. To avoid burn-out the current has to be switched off, i.e. the supplied superconducting magnet has to be discharged. The maximum possible operating current densities in the superconducting part of the current lead have been calculated assuming an exponential decay of the current with a time constant ~= 10s and allowing a maximum peak temperature of 400K in the current lead~ The operating current density should not exceed 500Acm -2 for the Bi-2212 bulk material, whereas values above 10 000 A cm -z are possible for Bi-2223/Ag tapes. In both cases it has been assumed that the current starts to decay when a voltage of 0.1 V has been developed across the superconducting part of the current lead.
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.
70 kA High Temperature Superconductor Current Lead Operation at 80 K
IEEE Transactions on Applied Superconductivity, 2006
For the superconducting magnet system of the International Thermonuclear Experimental Reactor, ITER, 60 current leads for a total current of more than 2500 kA are needed. To reduce the resultant large refrigerator load at 4.5 K, High Temperature Superconductor current leads (HTS-CL) could be used. Therefore, EFDA CSU Garching had launched a development program for a 70 kA HTS-CL demonstrator. The Forschungszentrum Karlsruhe and CRPP developed and built this CL optimized for 50 K Helium operation. In 2004, the CL was successfully tested in the TOSKA facility at the Forschungszentrum Karlsruhe. The very encouraging results lead to testing this CL with 80 K Helium because ITER provides a large 80 K Helium cooling capacity for the thermal shields. At the end of last year, the test could be successfully performed demonstrating that high current capacity current leads can be stably operated at about 80-85 K. Recently, the CL was retested using liquid nitrogen which would be an interesting alternative option.
High temperature superconducting current leads for the large hadron collider
IEEE Transactions on Appiled Superconductivity, 1999
The Large Hadron Collider (LHC) will be equipped with about 8000 superconducting magnets. Some 3380 leads will feed the currents ranging from 60 to 13000 A. To reduce the heat inleak into the liquid helium, CERN aims to use High Temperature Superconducting material for leads having current ratings between 600 and 13000 A. Specifications have been written for 13000 A current leads, incorporating a High Temperature Superconducting section, for the main magnets of the LHC, and contracts have been placed with several firms for the supply of prototypes for comparative testing. The leads used for feeding locally the 60 and 120 A dipole orbit correctors will be conventional conduction cooled resistive leads. An optimized lead of variable cross section has been tested, and an integral design has been initiated. This report describes the design status of the current leads for the LHC, emphasizing, for the different solutions, the principle of optimization and the choice of the cooling methods.
IEEE Transactions on Applied Superconductivity, 2017
There is a high potential to use high-temperature superconductors instead of conventional busbars in high direct current industrial applications. Since current leads are typically the major source of losses in these applications, we introduce and investigate the concept of a multistage cooled current lead for an operating current of 20 kA to minimize current lead losses. The design is based on the idea to realize an efficient and at the same time economic current lead that consists of components which are market proven and reliable. The current lead is down to 77 K and is cooled with two intermediate cooling stages at 240 K and 150 K. One key component is the joint between the resistive copper part and the YBCO high-temperature superconductor tapes, which is manufactured by a new soldering process. Moreover, electromagnetic Finite Element Analyses of a high-temperature superconductor stack design have been done to optimize the current carrying capacity of the current lead. As a result, the multistage cooled current lead is designed to cryogenic losses of 22.4 W/kA at 77 K.
Potential of High-Temperature Super Conductor Current Leads for LHC Cryogenics
1996
The reference design for the Large Hadron Collider (LHC) at the European laboratory for particle physics, CERN is based on the generalised use of HighTemperature Superconductor (HTS) current leads. This paper discusses the envisaged cooling methods for these HTS leads and lists the possible gains and drawbacks for the cryogenic system linked to these different solutions. The aspects considered for this comparison are the design of interfaces, the adaptability to load changes, the design of the heat exchangers for the lead cooling and the exergetic costs of refrigeration within the already well defined cryogenic infrastructure for the LHC machine.
Practical Design and Manufacturing of Cryogenic High Current Leads
High current leads are required in many large superconducting magnet facilities and will be required for high-temperature superconductor power applications. Several important factors must be selected in order to design high current leads that include the choice of conductor properties and lead geometry (length, cross section, cooling surface area). The application of a mathematical model and optimization for a 13-kA lead design between liquid helium and room temperatures are discussed. A design and manufacturing technology for current leads with specific heat leak near 1 W/kA in forced-cooled mode are also described. The principles of selection of the current-carrying element material, geometric sizes, and their influence on the heat leak from the current leads are explained. Measurements of the typical copper residual resistivity ratio found at different locations of welded samples taken from prototype current leads are presented. These measurements provide direction in choice of material properties used in modeling a current lead design. Different modes of cooling the current leads, such as vapor cooled and forced-flow cooled, are considered. A comparison between some existing current lead designs is discussed.
High Temperature Superconductor Current Leads for WENDELSTEIN 7-X and JT-60SA
IEEE Transactions on Applied Superconductivity, 2000
In the ITER superconducting magnet system, operation currents up to 68 kA are required that have to be transferred from room temperature (RT) to 4.5 K by specially designed current leads (CL). The ohmic losses and the thermal conduction of conventional CL cause high heat loads to the refrigeration system. This load can be reduced drastically by the use of High Temperature Superconductor (HTS) current leads because the superconducting HTS part of this CL causes no ohmic losses and very poor thermal conduction. The Forschungszentrum Karlsruhe and the CRPP Villigen have designed and built a 70 kA current lead using Bi-2223 HTS superconductor in the frame of the European Fusion Technology Programme. This HTS CL was installed and tested in the TOSKA facility of the Forschungszentrum Karlsruhe showing that the current of 68 kA can be carried by the CL even when the highest temperature in the HTS part is 85 K. The CL shows a large safety margin in case of a loss of coolant and even cooling with LN2 has been demonstrated. The option that all ohmic losses in the temperature range between 4.5 K and approx. 80 K can be eliminated using HTS CL is very attractive for ITER because savings in investment and operation costs are possible by removing this load from the cryogenic system. The consequences with respect to investment and operation costs are discussed comparing the ITER design with and without HTS CL which demonstrates that HTS current leads are very attractive and should be used for ITER.
The 100 kA current leads for a superconducting transmission line magnet
A pair of current leads to power a transmission line magnet cooled at liquid helium temperature has been designed and developed at Fermilab. The leads designed to carry 100 kA dc current. Each lead consists of a warm end, heat exchange section and a cold end. The warm end is a half moon plate and cylinder brazed together. The heat exchange section is made of 202 copper rods arranged in a staggered pattern. Each rod is 6.35 mm in diameter and 1650 mm in length. The rods were soft-soldered into 12.7 mm deep holes at both warm and cold ends. The helium gas flow, guided by anodized aluminum baffles along the lead length, allows for a relatively high heat transfer coefficient between the current carrying rods and cooling helium gas. As a result the current leads were successfully tested with a ramping current of up to 104 kA. The current lead design, assembly work and the test results are presented.