As the global warming gets worse, interest in renewable energy is increasing. Wind power is one of the main sources of the renewable energy. The capacity of wind generators has continued to increase. As the capacity of the wind turbine increases, the volume and weight of the head of the wind turbine also increase. Because of that, the capacity increase is limited. As a solution to this, studies are being conducted to increase the capacity of the generator and reduce the size and weight by using the characteristics of a superconductor having a high current density within the same volume. Most of them are partial superconducting generators that use superconducting wire only for field coils. If a superconducting wire is used for both the field coil and the armature coil, the advantages can be further maximized. Due to the nature of the superconducting wire having little resistance, there is little ohmic loss in the fully superconducting generator. However, the superconductor has a perfect diamagnetism, so it has a magnetic hysteresis and hysteresis loss due to AC magnetic fields. We have to consider the AC loss that has not been considered in the existing synchronous machine. AS the need for a wind generator with a larger capacity is growing, the conventional synchronous generator with copper armature coils cannot handle the weight of itself. Fully superconducting generators can be a solution if the AC loss is not so large. In this paper, the structure that can reduce AC loss was studied to increase the potential of the fully superconducting synchronous machine.
First, the concept of dual field windings was suggested. The magnetic field from the conventional superconducting field windings (single field windings) has a strong perpendicular field on the superconducting tape in the armature windings. Dual field windings decrease the perpendicular component.
A new concept for the structure of superconducting armature windings was also suggested. The superconducting coils in cryostats couldn’t be bent or twisted. So, the conventional structure for copper armature coils cannot be accepted. The new concept is that the 3 phase windings are installed in 4 poles span, so called 3 phase 4 pole winding. It makes a little more AC loss but can be realized.
Finally, a 10 MVA fully superconducting generator was designed. The amount of AC losses was affected by the gap in dual field windings and the size of the cross-section of the superconducting armature coils. The gap in dual fields was decided as 225 mm and the cross-section of the armature was decided by 16 mm × 64.8 mm.