Research projects:
Grand Challenge 2.2
For more information on this project, please contact Dr Steve Forrest
Manufacturing high performance coils and ultimate control
Manufacturing high performance coils and ultimate control
Led by The University of Sheffield
Led by The University of Sheffield
This Grand Challenge is concerned with manufacturing high performance electrical machine coils, with precision placement of conductors in the coil geometry, managed layer transitions and minimised end winding projections. The research is focussed on solid bar section bar conductors and hollow bar conductors, typically with a square crosssection or rectangular cross section with a small aspect ratio. An image of the solid bar conductor is shown (see right). A small duct through the centre of the hollow conductor allows for direct heat transfer, from the conductor to a fluid in the duct. Thus, a more robust insulation system can be employed which meets the electrical and mechanical requirements, since the dependency on heat transfer across the coil and the coil - stator core interface, through layers of electrical insulation, is removed. A hollow conductor thermal model and associated thermal test rig were established in Phase 1 of this Grand Challenge, along with an investigation of minimum bend radii, for both hollow and solid bar conductors. Further details can be found in the previous annual reports. Bar conductors enable greater utilisation of the stator slot area, which provides scope to increase the coil current density and hence the power density or torque density of the electrical machine. However, a typical electric machine for an automotive traction application can operate at speeds up to 12,000rpm, which equates to a fundamental frequency in the region of 1kHz. Future generation machines for automotive and aerospace applications may require even greater operating speeds. The AC losses in the winding, resulting from Eddy current and proximity effects, can be significant and require thorough consideration. The ongoing activities within Phase 2 of this Grand Challenge, are Multiple layer bar windings and high frequency characteristics of machines, focusing on AC loss modelling in bar windings in the first instance.