Analysis and Application of the Equivalent Circuit Model for Core Snubber

Abstract

Core snubber is a surge suppression protection device installed between the high voltage power supply and the auxiliary heating load. When a breakdown occurs, the core snubber can limit the short-circuit current and consume fault energy, thus protecting the high-voltage power supply and auxiliary heating load. The existing snubber schemes have the problems of large volume, high price, complex integrated design, and large inductance affecting the normal working current of the power supply, so a new expression of equivalent magnetization inductance is established based on the saturated wave theory. The equivalent circuit model of core snubber is improved, and the surge suppression characteristics of core snubber and the attenuation process of breakdown arc current are studied. The circuit model consists of a magnetized inductor and an eddy current resistor in parallel. The expression can be expressed by the characteristic parameters of the alloy winding, the structural size of the core and the voltage integral at both ends of the snubber. In this article, a prototype of iron-based nanocrystalline snubber is made, and a dc high-voltage short-circuit experimental platform is built. By comparing the simulation and measured results of the prototype, the accuracy of the snubber equivalent parallel circuit model derived in this article and its practicability in core design are verified. There are other circuit components in the breakdown discharge circuit of the auxiliary heating system in addition to the distributed capacitance and snubber. In order to further analyze the surge suppression characteristics and breakdown arc current attenuation process of the core snubber including other circuit components, in this article, the extended discharge circuit with reverse bias diode and secondary winding is simulated and tested. The influence of the bridge arm in the reverse bias state on the arc current in the high voltage uncontrolled rectifier during breakdown is discussed. In view of the thickness limitation of core strip, the effectiveness of reasonable setting of secondary winding to avoid core saturation is demonstrated through simulation and measured analysis.