Transposed-Cable Coil & Saddle Coils of HTS for Rotating Machines: Test Results at 30 K

We have manufactured and tested new HTS coil configurations in order to extend the range of rotating machines to which HTS tapes can be applied. The rotors of large utility generators require operating currents of several kA, which can be achieved by connecting several HTS tapes in parallel in a transposed cable. Design of a generator poses questions on winding technique for the coils, cooling technique at the required operating temperatures around 30 K, and V-I relation and stability of such coils. These questions were addressed by winding a test coil using 31 m of transposed cable comprising 500 m of BSCCO tape and testing it at 30 K. Smaller generators coupled to gas turbines have to work at many thousands of rpm. The high g-forces and need for compactness make it necessary to place the rotor coils as close as possible to the shaft, which requires coils with 3D-bent heads, like in accelerator dipoles. We have produced this type of coils with BSCCO tapes for the first time. After developing a winding technique using simple tooling, 700 m of BSCCO tapes were used to manufacture two 3D demonstrator coils, which were tested at 30 K as well. We describe winding methods, cooling technique and test results for both types of coils.