Design Strategies for an AC Loss Minimized Winding for a Fully Superconducting Wind Generator

As part of the German SupraGenSys project, a fully superconducting generator for wind energy conversion systems was investigated, which will be built and demonstrated as part of SupraGenSys 2. Therefore, this paper summarizes the main challenges and outlines the design strategy to achieve a design with low investment cost and high efficiency. The field winding and the armature winding consist of HTS tapes. The armature winding in particular has high alternating current losses due to the alternating magnetic field. These alternating current losses heat up the coils and must be compensated for by the cryocooler with high energy consumption. A highly efficient generator design can therefore still lead to a low overall efficiency of the system. Or a design with low AC losses can be achieved by using a large amount of HTS tapes, which increases the investment cost of the system significantly. In this paper, design strategies are published to achieve a generator design with low AC losses by identifying the factors that influences of AC losses and developing methods to reduce the losses. For this purpose, the tangential component of the flux density is investigated and the AC losses are determined using the TA formulation [Kim et al. (1962)]. Compared to the methods published in [2], this work focuses more on the overall design of the generator and its stator and rotor windings. The design is iron-based, which allows the use of the iron geometry to influence the AC losses and protect the stator winding from the rotor field. As a result, the AC losses are dominated by the intrinsic field of the coils, which can be influenced by the coil geometry. This enables a design with very low AC losses, high efficiency and modest use of HTS tapes.