Bi-2223 Field-Poles Without Iron Core for an Axial Type of HTS Propulsion Motor

We have conducted both electrical and cryomechanical designs of a superconducting propulsion motor based on field-poles made of twinned double-pancake-coils (DPC) with Bi-2223 superconducting wire. Neither field-poles nor armature coils have an iron core; that way the magnetic flux increases with increasing applied current in the HTS wire. Special attention has been paid to reducing heat from the coils upon excitation. We have fixed a final design with a low energy loss up to 0.25 W maximum excitation of 1.5 T, corresponding to a current of 200 A at 30 K. In the present study, we have assembled these 8 twinned DPCs into the HTS axial-gap type motor. The dimensions of the motor are 850 mm in diameter for 507 mm in length and the weight is 1044 kg for 100 kW at 230 rpm. The HTS field-pole coils were cooled by thermal conduction by using a circulation of condensed neon with a thermal siphon using a GM cryocooler. We report cryomechanical and technical issues. The successful excitation of the HTS rotor made of 8 twinned DPCs and the rotation test under low frequency are described.