Department of Engineering / Profiles / Dr Tim Coombs

Department of Engineering

Dr Tim Coombs

tac1000

Tim Coombs

Senior Lecturer

Academic Division: Electrical Engineering

Research group: Electronics, Power and Energy Conversion

Telephone: +44 1223 7 48315

Email: tac1000@eng.cam.ac.uk

Publications


Research interests

Over the last 20 years, the EPEC (Electronics, Power and Energy Conversion) superconductivity group, which I head, has built up an outstanding international reputation in several areas of superconductivity research, ranging from novel theoretical tools for the understanding of  superconducting properties up to real breakthroughs in the design of cutting-edge technologies. The group is now one of the strongest groups in the world with an extensive portfolio of experimental techniques and mathematical analysis tools. I have an internationally leading publication record which extends to more than 100 papers released in high impact scientific journals.

The group has been responsible for a number of notable firsts.  For instance, the EPEC group has been the world’s first group to:

  • Levitate a 40Kg flywheel on a superconducting bearing.
  • Propose and use the H-formulation for solving the critical state (a technique which is now very widely used).
  • Build and test the world's first all superconducting motor.
  • Test the feasibility of using an HTS insert in a superconducting magnet with a view to creating a 25 Tesla field.

Furthermore, it was one of the first groups to work on fault current limiters and is unique in having done so in three separate materials and with various geometries.  We have had several successful programs including one supported by EPSRC (EP/C512545/1) on the use of YBCO tape and another DTI sponsored effort in collaboration with Rolls Royce on the use of MgB2 wire in fault current limiters. These together with successful programs such as the LINK one with VA Technology have lead to sophisticated modelling and measurement facilities. We are using YBCO pucks as permanent magnets and YBCO tapes in the stator of a three phase synchronous motor. A further program in collaboration with Manchester, EADS and Rolls Royce is looking at the use of MgB2 in a wound stator together with a bulk YBCO based rotor is underway.

Another area of expertise is in superconducting magnetic levitation and the dynamics of different superconducting bearing systems. Aside from superconductivity, the group is active at looking at electrical distribution problems.  This encompasses studying partial discharge in switchgear, seasonal power factor variations and transformer design.

The Modelling effort that supports this work and other areas of investigation involves creating solutions to the critical state model and the E-J power law and has been going on for more than fifteen years. Using commercial finite element modelling software we obtained results on magnetic field, current distribution, magnetization decay, energy loss and quench of different superconducting objects including bulks, tapes, wires, coils, motors, etc. The models include AC/DC external magnetic field and transport currents. This work is internationally leading and includes:

  • One of the first algorithms capable of calculating the critical state in 2 dimensions
  • The first modelling environment which could describe the propagation of heat and the losses in a fault current limiting thin film
  • The first use of the H-formulation which is now the standard method used by most researchers

We are the world leaders in magnetisation of bulk superconductors using flux pumping techniques and I hold three ground breaking patents which cover both the flux pumping techniques and methods of patterning and arranging the magnets to enable high power density machines such as motors and generators (particularly wind turbines), as well as high-value machines such as accelerator magnets, MRI and MHD.

We have strong links with industry and have had collaborative projects sponsored by BMW, Rolls Royce, Areva, EDF Energy, VA Tech, Applied Superconductor, etc.  Equally, we have many links with colleagues in other universities and are currently collaborating with Manchester on the development and use of MgB2. As well as UK universities, we have strong links with other European (Liege, Jena and Barcelona) and American (Los Alamos, Argonne, Boeing) groups. We participated in an exchange program with Tshinghua University sponsored by the Royal Society and regularly accept visitors from Europe and America.

The group’s influence is also evident in its ability to consistently attract high profile and highly respected academic visitors together with a succession of highly motivated and extremely capable students who, almost without exception, have won scholarships and prizes of their own.

I have also been responsible for organising a series of workshops, on "the modelling and analysis of superconductors" and a summer school on "sustainable energy".

Finally, in addition to my university-based experience I spent a further ten years in industry, and have authored more than ten patents.

Strategic themes

Energy, transport and urban infrastructure

Ship Propulsion

Other positions

Director of Magnifye Ltd