Construction and Test of a Flux Modulation Superconducting Machine for Aircraft

International audienceThe increasing of drives towards More Electric Aircraft (MEA) or the development of electric propulsion aircraft calls for MW-class electrical machines with more compact and power dense designs. One way is to explore the use of superconducting materials to create a high magnetic field in order to reduce the mass of ferromagnetic components. This paper presents the construction and the test of a brushless axial flux superconducting machine. The brushless topology satisfies the aeronautics industry requirements in terms of maintenance, while the axial configuration ensures an optimal use of the anisotropic HTS tapes. The machine is classed as partially superconducting, only the inductor is made with superconducting materials. A special design concerning the use of a stationary cryostat is presented. This improvement reduces significantly the electromagnetic air-gap length. A 50kW prototype is manufactured with a minimal mass objective. The prototype constitutes a first step to a scale-up MW-class machine design

The mechanical properties of Y-Ba-Cu-O and Gd-Ba-Cu-O/Ag bulk superconductor magnets

Single-grain RE-Ba-Cu-O bulk high temperature superconductors [or (RE)BCO, where RE = rare earth element or yttrium] have demonstrated significant potential for practical applications due to their ability to trap magnetic fields in excess of 17 T, which is an order of magnitude greater than what can be achieved with conventional iron-based permanent magnets. One of the major obstacles to the use of (RE)BCO trapped field magnets is their poor mechanical properties, as bulk samples typically contain a large number of defects, such as pores and micro-cracks. Furthermore, significant electromagnetic stresses develop in bulk superconductors during magnetisation as a result of the Lorentz force, leading frequently to sample failure above around 10 T. Therefore, it is clear that the mechanical properties of bulk (RE)BCO need to be studied comprehensively and improved upon to realise the full potential of this technologically important material. This study first investigated the mechanical strength of YBCO single grains at room temperature by utilising three-point bend and Brazilian tests. This was followed by measurement of the mechanical deformation of GdBCO/Ag single grains in situ, i.e. during high-field magnetisation, to determine the strains and stresses experienced by the samples as a trapped field was established inside them at 64 K. Two techniques for improving the mechanical reliability of (RE)BCO bulk superconductors were subsequently developed. Firstly, samples of YBCO were melt-processed with artificial holes to reduce the defect population and to improve the intrinsic strength of the resultant single grains. As a result, the YBCO sample with artificial holes was able to survive significantly higher magnetisation fields and achieved a surface trapped field of 8.8 T at 30 K without any external reinforcement, which was not possible with the standard YBCO sample. Secondly, a composite structure was proposed, which involved reinforcing GdBCO/Ag single grains with stainless-steel sheets and shrink-fit stainless-steel rings. This preparation technique is also expected to improve the thermal stability of the overall structure. The first composite stack achieved 16.8 T and 17.6 T at 26 K and 22.5 K, respectively, in sequential magnetisation cycles, demonstrating the effectiveness of this reinforcement approach

Development of HTS trapped field magnet using 2G HTS coated conductors

Compact High-Temperature Superconducting (HTS) trapped field magnets stand at the frontier of breakthroughs for advanced industrial equipment, medical devices, and transportation electrification, offering capabilities that conventional permanent magnets and electromagnets cannot achieve. While superconductors capitalize on zero resistance to uphold high currents, thus generating substantial fields, traditional HTS bulks and stacks have been limited by constraints such as geometry size and mechanical robustness. As second-generation (2G) commercial HTS coated conductors advance, there's a growing emphasis on utilizing these tapes to attain expansive and stable trapped field profiles. This thesis explores the innovative magnetization mechanisms and design optimizations of HTS trapped field magnets fabricated with 2G HTS tapes through a comprehensive analysis of HTS-stacked ring magnets, hybrid HTS-stacked ring design, their mechanical stress responses, and trapped field closed-loop HTS coil under field cooling magnetization. The research primarily investigated a novel hybrid HTS trapped field magnet, integrating HTS-stacked ring magnets with HTS bulks to surpass traditional size limitations and achieve a significant trapped field of 7.35 T. It further predicted their capability to generate a trapped field exceeding the applied field due to unique induced current distributions and flux redistribution. Additionally, the study addressed the mechanical challenges posed by Lorentz forces during magnetization, presenting 3D numerical models to analyze stress and strain in HTS-stacked ring magnets. A 90 % stress reduction was seen by proper impregnation and fixation methods. Lastly, a novel closed-loop HTS coil approach was introduced, achieving a compact high-field superconducting magnet that trapped a central field 4.59 T which was higher than the 4.5 T applied field, showcasing potential for diverse high-field applications. Above the inner edge of the HTS coil, the trapped field exceeded the applied field by 1.5 T. This thesis combines experimental findings and numerical modelling to advance the understanding of HTS magnetization processes, offering insights into designing more efficient and durable compact and portable HTS magnets for applications in nuclear magnetic resonance, Maglev transportation, and HTS machineryCompact High-Temperature Superconducting (HTS) trapped field magnets stand at the frontier of breakthroughs for advanced industrial equipment, medical devices, and transportation electrification, offering capabilities that conventional permanent magnets and electromagnets cannot achieve. While superconductors capitalize on zero resistance to uphold high currents, thus generating substantial fields, traditional HTS bulks and stacks have been limited by constraints such as geometry size and mechanical robustness. As second-generation (2G) commercial HTS coated conductors advance, there's a growing emphasis on utilizing these tapes to attain expansive and stable trapped field profiles. This thesis explores the innovative magnetization mechanisms and design optimizations of HTS trapped field magnets fabricated with 2G HTS tapes through a comprehensive analysis of HTS-stacked ring magnets, hybrid HTS-stacked ring design, their mechanical stress responses, and trapped field closed-loop HTS coil under field cooling magnetization. The research primarily investigated a novel hybrid HTS trapped field magnet, integrating HTS-stacked ring magnets with HTS bulks to surpass traditional size limitations and achieve a significant trapped field of 7.35 T. It further predicted their capability to generate a trapped field exceeding the applied field due to unique induced current distributions and flux redistribution. Additionally, the study addressed the mechanical challenges posed by Lorentz forces during magnetization, presenting 3D numerical models to analyze stress and strain in HTS-stacked ring magnets. A 90 % stress reduction was seen by proper impregnation and fixation methods. Lastly, a novel closed-loop HTS coil approach was introduced, achieving a compact high-field superconducting magnet that trapped a central field 4.59 T which was higher than the 4.5 T applied field, showcasing potential for diverse high-field applications. Above the inner edge of the HTS coil, the trapped field exceeded the applied field by 1.5 T. This thesis combines experimental findings and numerical modelling to advance the understanding of HTS magnetization processes, offering insights into designing more efficient and durable compact and portable HTS magnets for applications in nuclear magnetic resonance, Maglev transportation, and HTS machiner

High-temperature superconducting ring magnet

Many electrical engineering applications such as motors and generators use permanent magnets which approximately account for 45% of their electricity consumption. The conventional magnets in use have a maximum field of around 1.5-2 T. High performance superconducting materials such as REBCO have facilitated the development of superconducting magnets. Superconducting bulk magnets and stacks of tapes have already demonstrated the extraordinary potential to trap magnetic fields of very high order with very compact sizes. This has significantly increased the efficiency of rotating machines and improved power/torque density, while having low synchronous reactance with large overloading capacity, high transient stability with low noise and harmonic content with the additional cost of cooling. This thesis focuses on a new type of superconducting magnet which uses superconducting tape as the field source. The most significant limiting factor for superconducting magnets is their size.;This new superconducting magnet has made possible the development of HTS magnets with flexible sizes by splitting the 2G HTS tapes to form the persistent current rings. By stacking HTS closed loop rings into a compact magnet, our HTS ring magnet has been proven to generate a trapped magnetic field higher than 5 T. The main advantage of the new magnet compared to existing trapped field HTS magnets is that the magnetic field lies parallel to the ab plane of the HTS, leading to higher critical currents in the same magnetic field. This thesis reports our key findings so far. Two different stacking configuration magnet samples were tested using the field cooling magnetization at 25 K and 4.2 K, with magnet diameter 90 mm and 150 mm, respectively. Over 4.6 T of the trapped field has been reported by using Super Power tapes with a field cooling process at 25 K, which is the highest field trapped in the ring magnets for first configuration. A new stacking design was proposed to improve magnetic field distribution within the magnet and has the potential to trap more magnetic field with the estimated trap field of 9.4 T at 4.2 K. A three dimensional model was developed to simulate the performance of the ring magnets, and good agreements between experiment and simulation have been achieved. The new HTS permanent magnet with improved field homogenisation and large diameter is promising for medical imaging applications, as well as propulsion applications.Many electrical engineering applications such as motors and generators use permanent magnets which approximately account for 45% of their electricity consumption. The conventional magnets in use have a maximum field of around 1.5-2 T. High performance superconducting materials such as REBCO have facilitated the development of superconducting magnets. Superconducting bulk magnets and stacks of tapes have already demonstrated the extraordinary potential to trap magnetic fields of very high order with very compact sizes. This has significantly increased the efficiency of rotating machines and improved power/torque density, while having low synchronous reactance with large overloading capacity, high transient stability with low noise and harmonic content with the additional cost of cooling. This thesis focuses on a new type of superconducting magnet which uses superconducting tape as the field source. The most significant limiting factor for superconducting magnets is their size.;This new superconducting magnet has made possible the development of HTS magnets with flexible sizes by splitting the 2G HTS tapes to form the persistent current rings. By stacking HTS closed loop rings into a compact magnet, our HTS ring magnet has been proven to generate a trapped magnetic field higher than 5 T. The main advantage of the new magnet compared to existing trapped field HTS magnets is that the magnetic field lies parallel to the ab plane of the HTS, leading to higher critical currents in the same magnetic field. This thesis reports our key findings so far. Two different stacking configuration magnet samples were tested using the field cooling magnetization at 25 K and 4.2 K, with magnet diameter 90 mm and 150 mm, respectively. Over 4.6 T of the trapped field has been reported by using Super Power tapes with a field cooling process at 25 K, which is the highest field trapped in the ring magnets for first configuration. A new stacking design was proposed to improve magnetic field distribution within the magnet and has the potential to trap more magnetic field with the estimated trap field of 9.4 T at 4.2 K. A three dimensional model was developed to simulate the performance of the ring magnets, and good agreements between experiment and simulation have been achieved. The new HTS permanent magnet with improved field homogenisation and large diameter is promising for medical imaging applications, as well as propulsion applications

DTT - Divertor Tokamak Test facility - Interim Design Report

The “Divertor Tokamak Test facility, DTT” is a milestone along the international program aimed at demonstrating – in the second half of this century – the feasibility of obtaining to commercial electricity from controlled thermonuclear fusion. DTT is a Tokamak conceived and designed in Italy with a broad international vision. The construction will be carried out in the ENEA Frascati site, mainly supported by national funds, complemented by EUROfusion and European incentive schemes for innovative investments. The project team includes more than 180 high-standard researchers from ENEA, CREATE, CNR, INFN, RFX and various universities. The volume, entitled DTT Interim Design Report (“Green Book” from the colour of the cover), briefly describes the status of the project, the planning of the design future activities and its organizational structure. The publication of the Green Book also provides an occasion for thorough discussions in the fusion community and a broad international collaboration on the DTT challenge

Tailoring Superconductor and SOFC Structures for Power Applications

High temperature superconductors (HTS) and solid oxide fuel cells (SOFCs) both offer the possibility for dramatic improvements in efficiency in power applications such as generation, transmission and use of electrical energy. However, production costs and energy losses prohibit widespread adoption of these technologies. This thesis investigates low-cost methods to tailor the structures of HTS wires and SOFCs to reduce these energy losses. Section I focusses on methods to produce filamentary HTS coated conductors that show reduced AC losses. This includes spark-discharge striation to pattern existing HTS tapes and inkjet printing of different filamentary architectures. The printed structures are directly deposited filaments and ‘inverse’ printed tracks where an initially deposited barrier material separates superconducting regions. Furthermore, the concept and first stages of a more complex ‘Rutherford’ cable architecture are presented. Additionally, Section I investigates how waste material produced during the manufacture of an alternative low-AC loss cable design, the Roebel cable, can be used to make trapped field magnets that produce a uniform magnetic field profile over a large area. This trapped field magnet work is extended to study self-supporting soldered stacks of HTS tape that demonstrate unprecedented magnetic field uniformity. Section II looks at how nanostructuring porous SOFC electrodes via solution infiltration of precursors can improve long-term stability and low temperature performance. Inkjet printing is utilised as a scalable, low-cost technique to infiltrate lab-scale and commercial samples. Anode infiltration via inkjet printing is demonstrated and methods to increase nanoparticle loading beyond ~1 wt% are presented. Symmetric cells with infiltrated cathodes are shown to have improved performance and stability during high temperature aging. Additionally, the sequence of solution infiltration is found to be important for samples dual-infiltrated with two different nanoparticle precursors.EPSR

AMSAHTS 1990: Advances in Materials Science and Applications of High Temperature Superconductors

This publication is comprised of abstracts for oral and poster presentations scheduled for AMSAHTS '90. The conference focused on understanding high temperature superconductivity with special emphasis on materials issues and applications. AMSAHTS 90, highlighted the state of the art in fundamental understanding of the nature of high-Tc superconductivity (HTSC) as well as the chemistry, structure, properties, processing and stability of HTSC oxides. As a special feature of the conference, space applications of HTSC were discussed by NASA and Navy specialists

Proceedings of the 4th International Conference and Exhibition: World Congress on Superconductivity, volume 1

The papers presented at the 4th International Conference Exhibition: World Congress on Superconductivity held at the Marriott Orlando World Center, Orlando, Florida, are contained in this document and encompass the research, technology, applications, funding, political, and social aspects of superconductivity. Specifically, the areas covered included: high-temperature materials; thin films; C-60 based superconductors; persistent magnetic fields and shielding; fabrication methodology; space applications; physical applications; performance characterization; device applications; weak link effects and flux motion; accelerator technology; superconductivity energy; storage; future research and development directions; medical applications; granular superconductors; wire fabrication technology; computer applications; technical and commercial challenges, and power and energy applications

Fourth International Symposium on Magnetic Suspension Technology

In order to examine the state of technology of all areas of magnetic suspension and to review recent developments in sensors, controls, superconducting magnet technology, and design/implementation practices, the Fourth International Symposium on Magnetic Suspension Technology was held at The Nagaragawa Convention Center in Gifu, Japan, on October 30 - November 1, 1997. The symposium included 13 sessions in which a total of 35 papers were presented. The technical sessions covered the areas of maglev, controls, high critical temperature (T(sub c)) superconductivity, bearings, magnetic suspension and balance systems (MSBS), levitation, modeling, and applications. A list of attendees is included in the document

Nuclear Fusion Programme: Annual Report of the Association Karlsruhe Institute of Technology/EURATOM ; January 2013 - December 2013 (KIT Scientific Reports ; 7671)

The Karlsruhe Institute of Technology (KIT) is working in the framework of the European Fusion Programme on key technologies in the areas of superconducting magnets, microwave heating systems (Electron-Cyclotron-Resonance-Heating, ECRH), the deuterium-tritium fuel cycle, He-cooled breeding blankets, a He-cooled divertor and structural materials, as well as refractory metals for high heat flux applications including a major participation in the preparation of the international IFMIF project