HTS Axial Flux Permanent Magnets Electrical Machine Prototype: Design and Test Results

A prototype of high-temperature superconductors (HTS) Axial Flux Permanent Magnets, Synchronous Machine in a single-side configuration is presented. The stator and the rotor disc have the same outer diameter Dout of 316 mm and its air gap is set at 5 mm. HTS coils placed on the stator disc and permanent magnets placed on the rotor disc have been used to assemble the Y-connected ironless armature concentrated winding and the field winding, respectively. Each phase of the armature winding is composed by two coils connected in series, although the ac power loss is the key problem: this might be less important for wind turbine applications interested by low armature frequency. Preliminary tests at the liquid nitrogen temperature on the prototype in generator and motor mode at different load conditions have been conducted in our laboratories: the characteristic curves (power, torque, efficiency, etc.) at different rotational speed are reported. A proper response at 77 K has been provided by the prototype so that HTS coils can be used to assemble armature windings for low-frequency applications. The test results show that the HTS permanent magnet machines in the axial flux configuration are more compact, efficient, and light weight than their conventional counterpart.