Design and testing of the 40 kV/20A solid-state switch based on SiC MOSFETs for ECRH on J-TEXT Tokamak

Abstract Cathode power supply provides high voltage and large energy for electron gyrotron on J-TEXT tokamak. When faults (e.g. internal arc fault) happen on electron gyrotron, the power supply should interrupt within few tens of microseconds. Although the cathode power supply could switch off quickly by itself, frequent failures could decrease the reliability of the power supply without additional protection measures. For the safety of electron cyclotron resonance heating (ECRH) system, solid-state switch is necessary in ECRH protection. A design of a 40 kV/20A solid-state switch was proposed in this paper. To improve the switching performance of the switch, the power devices connecting in series was silicon carbide (SiC) metal-oxide-semiconductor field-effect transistor (MOSFET), which replaced traditional solution such as silicon (Si) insulated gate bipolar transistor (IGBT). For the purpose of evaluating and comparing the characteristic of SiC MOSFET and Si IGBT, a dual-pulse test was completed and SiC MOSFET showed the significant advantages. Furthermore, a voltage-clamped snubber circuit was adopted to ensure the voltage balance for each SiC MOSFETs during static and dynamic process. Then, the analysis and validation of the circuit was provided. Finally, the solid-state switch was built and tested by experiment. The results show that the switch works adequately, the switching-off time is 4.7us with 38 kV voltage and 20A current capacity.