Parametric study for the cooling of high temperature superconductor (HTS) current leads (original) (raw)

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.

Development of binary superconducting current leads with a gas cooled normal part

Cryogenics, 1994

The design of a binary superconducting 1 kA current lead, operating between 300 K and 4.2 K, will be presented. The normal conducting part of the lead, will be cooled by high pressure helium gas of 60 K inlet temperature. The resulting warm end temperature of the conduction cooled high-temperature superconductor (HTSC) part is about 67 K and as a consequence a magnetic stray field of 0.2 T can be tolerated. A total heat load of 012 W at 4.2 K has been foreseen. The required room temperature power input of the refrigerator is reduced to about 25 % as compared to an optimised conventional current lead.

Conceptual design and analysis of a cryogenic system for a new test facility for high temperature superconductor current leads (HTS CLs)

Przeglad Elektrotechniczny

In view of the R&D program on HTS CL at EPFL-CRPP PSI Villigen it is foreseen to extend the capabilities of an existing facility (JORDI) in order to be able to perform tests of HTS CL in different conditions. The present work is focused on the conceptual design of the cryogenics needed for the facility upgrade considering the requirement of an as extended as possible range of operation. Two cooling options for the copper part of a CL are considered. The use of heat exchangers for the optimization of the cryogenic system is discussed and their size is assessed.

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.

Design of conduction cooling system for a high current HTS DC reactor

Journal of Physics: Conference Series, 2017

A DC reactor using a high temperature superconducting (HTS) magnet reduces the reactor's size, weight, flux leakage, and electrical losses. An HTS magnet needs cryogenic cooling to achieve and maintain its superconducting state. There are two methods for doing this: one is pool boiling and the other is conduction cooling. The conduction cooling method is more effective than the pool boiling method in terms of smaller size and lighter weight. This paper discusses a design of conduction cooling system for a high current, high temperature superconducting DC reactor. Dimensions of the conduction cooling system parts including HTS magnets, bobbin structures, current leads, support bars, and thermal exchangers were calculated and drawn using a 3D CAD program. A finite element method model was built for determining the optimal design parameters and analyzing the thermo-mechanical characteristics. The operating current and inductance of the reactor magnet were 1,500 A, 400 mH, respectively. The thermal load of the HTS DC reactor was analyzed for determining the cooling capacity of the cryo-cooler. The study results can be effectively utilized for the design and fabrication of a commercial HTS DC reactor.

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.

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.

Conceptual design of current lead for large scale high temperature superconducting rotating machine

T. D.Le, J. H. Kim, S. I. Park, and H. M. Kim, 2014

"High-temperature superconducting (HTS) rotating machines always require an electric current of from several hundreds to several thousand amperes to be led from outside into cold region of the field coil. Heat losses through the current leads then assume tremendous importance. Consequently, it is necessary to acquire optimal design for the leads which would achieve minimum heat loss during operation of machines for a given electrical current. In this paper, conduction cooled current lead type of 10 MW-Class HTS rotating machine will be chosen, a conceptual design will be discussed and performed relied on the least heat lost estimation between conventional metal lead and partially HTS lead. In addition, steady-state thermal characteristic of each one also is considered and illustrated."

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.

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.