Protection properties of HTS coil charging by rotary HTS flux pump in charging and compensation modes

Protection properties of HTS coil charging by rotary HTS flux pump in charging and compensation modes

The low normal zone propagation velocity (NZPV) of high-temperature superconducting (HTS) tape leads to a quench protectionproblem in HTS magnet applications. To overcome this limitation, various studies were conducted on HTS coils without turn-toturn insulation (NI coils) that can achieve self-protection. On the other hand, NI coils have some disadvantages such as slowcharging and discharging time. Previously, the HTS coils with turn-to-turn insulation (INS coils) were operated in power supply(PS) driven mode, which requires physical contact with the external PS at room-temperature, not in persistent current mode. Whena quench occurs in INS coils, the low NZPV delays quench detection and protection, thereby damaging the coils. However, therotary HTS flux pump supplies the DC voltage to the superconducting circuit with INS coils in a non-contact manner, which causesthe INS coils to operate in a persistent current mode, while enabling quench protection. In this paper, a new protection characteristicof HTS coils is investigated with INS coils charging through the rotary HTS flux pump. To experimentally verify the quenchprotection characteristic of the INS coil, we investigated the current magnitude of the superconducting circuit through a quench,which was intentionally generated by thermal disturbances in the INS coil under charging or steady state. Our results confirmedthe protection characteristic of INS coils using a rotary HTS flux pump.

The low normal zone propagation velocity (NZPV) of high-temperature superconducting (HTS) tape leads to a quench protectionproblem in HTS magnet applications. To overcome this limitation, various studies were conducted on HTS coils without turn-toturn insulation (NI coils) that can achieve self-protection. On the other hand, NI coils have some disadvantages such as slowcharging and discharging time. Previously, the HTS coils with turn-to-turn insulation (INS coils) were operated in power supply(PS) driven mode, which requires physical contact with the external PS at room-temperature, not in persistent current mode. Whena quench occurs in INS coils, the low NZPV delays quench detection and protection, thereby damaging the coils. However, therotary HTS flux pump supplies the DC voltage to the superconducting circuit with INS coils in a non-contact manner, which causesthe INS coils to operate in a persistent current mode, while enabling quench protection. In this paper, a new protection characteristicof HTS coils is investigated with INS coils charging through the rotary HTS flux pump. To experimentally verify the quenchprotection characteristic of the INS coil, we investigated the current magnitude of the superconducting circuit through a quench,which was intentionally generated by thermal disturbances in the INS coil under charging or steady state. Our results confirmedthe protection characteristic of INS coils using a rotary HTS flux pump.