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.