Time: Tuesday, Dec 27, 2011, 01:30 pm ??03:00 pm
Venue: Xiang-Xian Auditorium, Dept. of Mechanical Engineering, National Cheng Kung University (Tzu-Chiang Campus)
Speaker: Dr. Tim Coombs, Senior Lecturer, Engineering Department
University of Cambridge, UK
Biography:
Dr. Tim Coombs is currently a senior lecturer in the Electrical Power Engineering and Energy Conversion group at Cambridge University?? Engineering Department. He researches into applications of superconductivity especially High Temperature Superconductors and specifically YBCO. He has a large and active group who are currently working on motors, generators, energy storage, dipole magnets, AC losses and the analysis of critical currents. His research covers both wires and tapes and also bulk superconductivity and of especial interest is the magnetisation of bulk YBCO which when magnetised can sustain a magnetic field an order of magnitude greater than that of conventional magnetic materials.
Abstract:
The Electrical Power and Energy Conversion (EPEC) superconductivity group at Cambridge University has been working on the application of superconductivity to large scale devices. This work is taking place over a range of areas which cover FCLs, motors and generators, SMES, accelerator magnets and MRI. The research is underpinned by advanced modelling techniques using both pure Critical State models and E-J models to analyse the behaviour of the superconductors. As part of the device design we are concentrating on the analysis of AC losses in complicated geometries such as are found in motor windings and the magnetisation of bulk superconductors to enable their full potential to be realised. We are interested in the full range of high temperature superconductors and have measured and predicted the performance of YBCO, MgB2 and BSCCO at a range of temperatures and in wire, tape and bulk forms. We are especially interested in large scale machines such as wind turbines or marine drives.This paper concentrates on recent work which in addition to the machines work includes: modelling of coils using formulations based on H and the vector potential A, crossed field effects in bulk superconductors; a magnetic model together with experimental results which explain and describe the method of flux pumping whereby a bulk superconductor can be magnetised to a high flux density using a repeatedly applied field of low flux density and finally a new configuration for MRI magnets.
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