Design considerations for electric motors using stacks of high temperature superconducting tape as permanent magnets

High temperature superconducting (HTS) tape can be cut and stacked to form composite bulks capable of generating fields as high as 17.7 T, the highest of any trapped field magnet. This makes them the most powerful permanent magnets accounting for the need to maintain a cryogenic temperature. This cryogenic penalty is increasingly being justified due to the significantly higher power densities (>10kW/Kg) fully superconducting motors can enable by using magnetized stacks of tape on the rotor and HTS coils on the stator. Design considerations for a motor using magnetized stacks for aerospace applications will be presented including FEM modelling in COMSOL and experimental prototype results for candidate designs. The rotor AC loss due to heating by ripple fields will be discussed based on these results and its interdependence with stator AC loss in a fully superconducting motor which has not always been appreciated in previous partially superconducting motor designs.