Design of the Cryogenic System for a 400 kW Experimental HTS Synchronous Motor

A 400 kW radial-axial flux type experimental HTS synchronous motor is designed. There are twelve armature coils used HTS wires in the motor. They are accommodated in the cooling vessels made of FRP material, and twelve cooling vessels are enclosed in the vacuum vessel. In order to cool the HTS coils of the motor, a sub-cooled liquid nitrogen cryogenic system is presented. The operation temperature is below 70 K. This system consists of HTS coils cryostats, liquid nitrogen transfer-line, liquid nitrogen dewar and a cold box with liquid nitrogen pump, G-M cryorefrigerators and some control valves inside. In this paper, different kinds of the heat loads of the system including the AC loss, current lead, supporters and radiation are presented. Basis on the heat load and operating temperature, the main parameters and equipments of the system are determined.