Design of Indirect Closed-Cycle Cooling Scheme Coupled With a Cryocooler for a 3-MW-Class High-Temperature Superconducting Synchronous Motor

The increase in the heat generated from high-temperature superconducting (HTS) rotating components limits the applicability of a cooling method. Hence, a liquid cooling and convection cooling scheme for high-heat-flux applications has gained interest. An indirect closed-cycle cooling scheme coupled with a cryocooler is an alternative cooling technique, in which the heat of vaporization is transferred from an evaporator to a condenser with a relatively small temperature difference. The cooling system of a demonstrative 3-MW-class HTS motor is presented in this paper. A cryogen was used to maintain uniform temperature of the field coil; the maximum temperature of the HTS coils was approximately 30 K during normal operation. The operation process of the cooling system is illustrated, and the main circulation parameters, namely, cryogen flow rate and the heat flux of cooling system, are investigated.