HTS magnet for maglev applications (2) - Magnet structure and performance

An HTS magnet. for maglev application has been developed. The magnet consists of four persistent-current HTS coils, and is operated at a rated temperature of 20 K and a rated magnetomotive force of 750 kA for each coil. This paper describes the structure and performance test results of the HTS magnet. The four HTS coils are installed in a cryostat and conductively cooled by two sets of two-stage GM type pulse tube cryocoolers below 20 K. Detachable current leads, which are composed of connectors and ultrasonic motors, are adopted to reduce the heat leakage to the 1st stage cold head of the cryocoolers. The HTS coils are simultaneously charged up to the rated magnetomotive force. Persistent current operating tests were carried out and the current decay rates of 0.4-0.7 %/day were attained. Also, in order to evaluate the mechanical capability of the magnet, vibration tests were conducted and permissible vibration responses were obtained.