Study on Reducing the Maximum Perpendicular Magnetic Field of HTS Coils Used on Synchronous Generator Armatures

In this paper, a 30-kW permanent magnet superconducting synchronous generator is proposed for the marine application. The perpendicular magnetic field on the high temperature superconducting (HTS) coils will cause a large drop in critical current and create much more ac loss. The magnetic field consists of two parts, i.e., self-field created by the transport current and external field created by the rotor rotation. It can be reduced by decreasing the distance between the HTS coil and back iron, increasing the distance between the HTS coil and iron teeth or adding the slot wedges in the open slots. These are effective methods to improve HTS armatures' critical current by reducing the perpendicular magnetic field on the HTS coil surface. Changing the turns ratio of HTS coils has little influence on reducing the maximum perpendicular magnetic field. However, it could decrease the number of flux lines passing through the HTS coil and reduce the total ac loss of the HTS coil