Time delay of triggered vacuum switch based on heat conduction model

The triggered vacuum switch (TVS) is a normally nonconducting device in which a high-current metal-vapor arc can be established by a suitable pulse of current to a triggering electrode. It is suggested that the initial breakdown of the trigger gap occurs in the gases desorbed from the surface of the dielectric coated on the cathode due to Joule heating. The trigger arc and cathode spots are responsible to build up the glow discharge in the trigger gap and lead to the breakdown in the main gap in the positive polarity case. Based on the behavior of heat in cathode electrode, a heat conduction model was set up for describing the heating process of the spots on the cathode in this paper. The model was tested by calculating the time delay of a triggered vacuum switch and experimentally validated. The calculations were carried out by dividing the triggering process into three stages. The first stage is the time for building up glow discharge and start arc in trigger gap. The second stage is the time for initial trigger plasma to chute to main gap. The last stage is the time for initial plasma triggering an arc in main gap. Experiments were conducted on a triggered vacuum switch with a TiH-loaded trigger cathode. The basic structure of triggered vacuum switch and test circuit were depicted. The calculation results confirm with experimental data very well. It shows evidence in favor of the heat conduction model.