Damper Screen Design in HTS Medium Speed Wind Generators Considering Stator Current Harmonics

High-temperature superconducting field windings have the potential to increase the torque and power density of synchronous wind generators by more than a factor of two, compared to the state-of-the-art permanent magnet excitation. The required amount of superconducting material is comparably small, if used in geared, compact medium speed generators
$(n\approx 400\ldots 600 \text{rpm})$
. For this concept, avoiding losses in the cryogenic rotor section is mandatory to limit the required cooling power and the cost of the cooling system. As preliminary work for the intended build-up of a full-size demonstrator with 13 MW power rating, the eddy current loss in the cryostat wall and the cold rotor iron is studied for different stator feeding variants. The use of a warm copper damper screen is identified as effective measure to limit the harmful additional losses due to stator current harmonics.