Pulsed-field magnetization of bulk HTS magnets in twinned rotor assembly for axial-type rotating machines

We study the pulsed-field magnetization of HTS bulks and its application to a rotating synchronous machine of axial-gap type. To increase the output performance of the rotating machine, the multiple rotor structure is designed with the alternation of the rotor with Gd-bulks and the fixed armature. Thus, we obtain a redundancy for the rotor magnet operation without additional current leads or slip rings. To assess the present redundancy, we show the result of the pulsed-field magnetization for Gd-bulks in the above-mentioned multiple rotor geometry. Two Gd-bulks 60 mm in diameter and 19 mm thick were inserted into three vortex-type Cu coils. They were immersed in liquid nitrogen. The pulsed current was applied to three serial vortex-type coils. The maximum applied magnetic filed was 5.7 T with a rise time of 6.6 ms. The trapped fields for the two Gd-bulk were 0.851 and 0.835 T, respectively. We showed that it is possible to perform pulsed-field magnetization for two Gd-bulks sandwiched between three armature vortex-type Cu coils, i.e., a double-layered twin rotor assembly.