Translated Abstract
Vacuum arc is a metal vapor arc in a vacuum environment. When arc current is low and the anode is not active, the plasma and the metal vapor produced from the cathode spot are the predominant factors to sustain the burning of the vacuum arc, which is the essential difference between the vacuum arc and other gas arcs. Further more, the motion and distribution of multiple cathode spots in high-current vacuum arc have great influence on the distribution of the arc plasma, the shape of arc, and the interruption performance of vacuum switches. In this thesis, the motion characteristic of single cathode spot of vacuum arc was mainly researched with modeling and simulation, and experimentally investigation.In the absence of external magnetic field, the motion of cathode spot is random walk. With external transversal magnetic field, the cathode spot moves in the reverse direction of the ampere force, which is called retrograde motion. However, the retrograde motion of cathode spot is just a macroscopic phenomenon. Actually, even in a strong magnetic field, there appears random motion, even the motion in ampere direction, in short time scale. Thus the random motion is an essential characteristic of cathode spot. In this thesis, a two-dimensional probability density distribution model on the motion of cathode spot of vacuum arc was developed with the method of statistics. With the model, the probability distribution of random motion without magnetic field and retrograde motion under different external magnetic field was simulated.In this thesis, the motion characteristic of cathode spot was further researched by experiments. The experimental circuit, the electrode, and the arc triggering system were designed. To generate the vacuum arc with single cathode spot, the starting arc circuit of the high-voltage synthesis circuit was used to generate a low direct current. A large numbers of experiments on low-current vacuum arc were conducted in a detachable vacuum arc chamber. The images of the motion of cathode spot were photographed by a high speed camera. The probability distribution of the motion, the average displacement and velocity of cathode spot were studied with emphasis by processing the photos of cathode spot in multiple experiments. The experimental results agreed well with the simulation results. According to the experimental results, the influence of some factors, e.g., the electrode space, the arc current and the condition of the cathode surface, on the motion of cathode spot and some other phenomena appearing in experiment, such as the arc current noise, had been analyzed in this thesis.
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