Analysis to core snubber based on Deltamax

Core snubber is one of the most important devices in EAST (Experimental Advanced Superconducting Tokamak) NBI (Neutral Beam Injector) system. This device is designed to protect the NBI system during periods of high voltage breakdown. The theory for the core snubber was developed by Fink, Baker and Owen (FBO model) who considered only the resistance effects and gave snubber design based on saturation conditions. The paper presents an approach to limit the high voltage breakdown effects based on the concepts of the equivalent resistance and inductance in a parallel mode implemented with Deltamax cores. After that, the EAST NBI circuit fault simulation code is primarily established which could simulate fault conditions with above time-varying resistance and inductance. The code is calibrated with the test results. Based on above work, the ion source snubber is designed with Deltamax. This snubber is tested at 50kV in NBI system which has large gradient capacitor and a peak short current less than 400A. The results show that it can protect ion source reliability and verify the modeling method.