Modeling, Simulation, and Analysis of the HV Snubber

The snubber is a transformer-like fault-protection device in the heating neutral beam of a fusion device, such as the ITER, which is designed to suppress the short-circuit current and protect the ITER during High Voltage sparking. To study the working principle of the snubber in depth, an accurate simulation model was developed in Simulink based on an improved parallelogram hysteresis model generated its nonlinear equivalent circuit. By comparing the simulations with the test results, the accuracy of the simulation model was verified with satisfactory agreement for their benign electromagnetic compatibility design. Then, the simulation model was used to analyze the dynamic response of the snubber when sparking occurred. The leakage inductance of the transmission line could naturally suppress the measured first spike of the fault-current pulse, which was elusive before. However, too large a leakage inductance will enhance the main peak of the fault-current pulse, which is suggested to be <0.6 kA. The measured sawtooth wave was simulated out using two snubbers with different cores. The design parameters of the ITER snubber were further analyzed with it on stray capacitance of the ITER Heating Neutral Beam system, which raises concerns as to its safety. Advanced snubber design is suggested for a safer ITER or CFETR.