A High-Voltage Solid-State Switch Based on Submodule Topology of SiC MOSFETs for J-TEXT Tokamak

Due to safety and reliability concerns, high-voltage solid-state switch is required for electron cyclotron resonance heating system on J-TEXT Tokamak. It cuts off the power supply within a little time usually in microseconds, when a fault occurs. At present, wide-bandgap semiconductors based on silicon carbide (SiC) show superior material properties enabling potential power device operation at higher voltage, current, and switching speeds than current silicon (Si) semiconductors. SiC metal–oxide–semiconductor field-effect transistors (MOSFETs) are considered to be a better solution for the basic component of the switch than Si insulated gate bipolar transistors (IGBTs). To solve the problem of voltage balancing in series-connected MOSFETs, a submodule with four, 1.7 kV/40 A rated MOSFETs in series has been developed and experimentally tested. A voltage-clamped snubber circuit is designed to control the overvoltage of each MOSFET. The turn-off performance of the proposed circuit and traditional circuit has been compared by simulation, and the submodule has also been evaluated in a dual-pulse test. Finally, the solid-state switch with 16 submodules in series has been tested by a dummy load. The experimental results show that switch can operate successfully, and the switching performance satisfies the anticipated demand.