Development of an HTS motor with Ho-123 superconducting field coils at liquid nitrogen temperature

A 22kW, 360RPM, 8-pole high temperature superconducting (HTS) synchronous motor with Holmium (Ho)-123 field coils at liquid nitrogen temperature was designed, manufactured and tested. This motor employs an axial gap rotating-armature construction and consists of one field assembly and two armature assemblies. The field employs eight single pancake coils which are wound with the world's first developed Ho-123 HTS wire. Ho-123 wire has potential high critical current density, which is expected to be as large as 100 times of BSCCO wire. Each coil is wound with 15m wire and the field can carry 75A current at liquid nitrogen temperature. We investigated coils AC behaviour and proposed a new way to minimize AC loss. A new method to suppress field current ripple is employed in this motor. A large variety of motor experiments were carried out and compared to the 3D model analysis that was conducted by Finite Element Method (FEM) showing the results met all its design goals. This paper provides the key designs of the motor, the analysis, tests of field coils and the motor.