This paper reviews the recent development of mobile nondestructive evaluation (NDE) systems using high-Tc superconducting quantum interference devices (SQUIDs) for conductive materials and structures. The contents of this paper include a noise cancellation scheme using active shielding, a novel high-Tc SQUID gradiometer with robustness in magnetic fields, mobile SQUID NDE systems and NDE of complex composite-metal structures. Using the novel high-Tc SQUID gradiometer, the superior capability of the mobile SQUID NDE system compared to conventional NDE techniques is demonstrated and discussed.
The development of superconducting rotating machines based on metallic superconductors achieved many excellent results, for example, in the Super-GM project. However, since the end of the 20th century, the focus of development has shifted to developing high-temperature superconducting (HTS) machines. The initial target application was industrial motors for pumps and fans, but this has now changed to low-speed large-torque motors for ship propulsion. Recently large-capacity wind turbine generators have been attracting attention. Furthermore, the development of fundamental technologies for HTS turbine generators in thermal and atomic power stations has started. Excellent features such as smaller size, lighter weight and higher efficiency, and also improvement of functions and characteristics are expected in superconducting rotating machines. However, cost reduction and system reliability verification are still key issues for practical application of the HTS machines. This article describes superconducting rotating machine technologies and technical trends in their development, the fundamental structure and characteristics of the rotating machines, the Super-GM project based on the liquid helium cooling and NbTi metallic superconductor, and the development status of HTS rotating machines.
Development and introduction of wind power generation have recently advanced in the R & D of renewable energies. Scaling-up of wind turbines is one of recent R & D trends because of the scale merits. In the wind farms in Europe, a significant number of 5 MW turbines are being installing. Further increase in the turbine size is expected. There are high expectations for a break-thought technology that will enable to develop light weight and compact wind turbine generators with large capacity of more than 10 MW. Applying high temperature superconducting (HTS) technology to the wind turbine generators can provide the light weight and compact design, since the magnetic field can be higher than that of conventional generators and the iron core can be considerably reduced. Therefore, it is considered that the application of the HTS technology to the wind turbine generator is one of the key issues to overcome the technical power limit of conventional wind turbine generators. This article reviews the recent technical trends of large capacity wind turbine generators and related R & D problems. In the article, the recent studies on the electromagnetic design of the HTS wind turbine generators are reviewed. The features of the design of HTS wind turbine generators are summarized.
An industry-academia research group, of which IHI Corporation is a representative, has performed trial manufacturing of several axial-gap synchronous motors with superconducting windings cooled by liquid nitrogen. In the development of these motors, we were faced with issues of AC loss and current imbalance among the coils connected in parallel due to the inductance difference, which are characteristic of AC applications of superconductors. We took measures for these issues and validated them in a newly constructed motor with a rated power of 400 kW. In this paper, the progress of our motors and a brief summary of the results of the load test for the latest motor are introduced.
Although the application of superconductivity technologies to rotating machines has been studied since the 1970s, it has not yet been made practicable. However, due to the recent rapid improvements in high-temperature superconductor performance, high-temperature superconducting motors for ship propulsion are approaching a level where they can be utilized. In this article, the current status of R&D on high-temperature superconducting motors for ship propulsion being developed by Kawasaki Heavy Industries Ltd. (KHI) and its cooperative research groups is reported. In particular, the aims, content and plans of two projects being led by KHI will be shown. The first one is the New Energy and Industrial Technology Development Organization (NEDO) energy-saving project, and the second one is the Japan Science and Technology Agency (JST) SInnovation project. Finally, a roadmap and further studies related to the practical application of high-temperature superconducting motors for ship propulsion are shown.
This paper reviews the current status of high-temperature superconducting induction/synchronous machine developments. The novel performance of the machine is explained through analysis and experiments. Furthermore, realizable uses of the machine in both large-capacity and intermediate-sized applications are discussed for industrial innovation. The development status of some applications in such machines as electric vehicles, electrified railway systems, generators and liquidhydrogen circulation systems, is summarized and discussed.
Since wind power generation systems operate at very low rotation speeds, synchronous generators that apply hightemperature superconductors (HTS) to the field windings provide merits such as significant reductions in size/weight and improved rating/partial load efficiency. In this study, a conceptual structure of the HTS generators with a salient-pole iron rotor and racetrack-shaped HTS field coils was proposed. The electrical designs of the large-scale salient-pole HTS generators were prepared using the design program developed. In the design, operating field current was determined from the allowable HTS coil heat loss, which was calculated using three-dimensional magnetic flux analysis. The influence of magnetic flux density in rotor iron cores and the number of poles on elements of main-generator performance such as generator weight, generator efficiency and the required HTS length were clarified. Furthermore, the suitable stator outer diameter for a given output power was studied in order to obtain satisfactory generator performance. Machine parameters were determined considering these results, and electrical designs of 5-10 MW HTS generators were created under an operating temperature of 77 K.