Simulation Study On The MHD Model Of Vacuum Arc With Rotating Electrodes

Vacuum circuit breaker is named for its high vacuum of the insulating medium in the contact gap of the and the contact gap after the arc extinguishing,which have many advantages such as good airtightness,small contact gap,short arc duration,low arc voltage,small arc energy,simple structure,small volume,light weight,suitable for frequent operation,etc.Vacuum circuit breaker is widely used in medium-voltage power transmission and distribution system with its excellent arc extinguishing performance,and is developing into high-voltage power transmission and distribution system.Therefore,how to improve the capacity of vacuum circuit breaker has become a hot research topic.Based on the previous vacuum arc model,this paper proposes to change the motion mode of the electrode during the breaking process,and explores the changes of the flow parameters and electromagnetic parameters of the vacuum arc under the rotation of the electrode,and provides a theoretical basis for improving the breaking capacity of the vacuum circuit breaker by using the simulation results.Different from the process of arc extinguishing in gas medium,the contact surface of the electrode of vacuum circuit breaker is involved in the whole process of vacuum arc combustion,so the process of vacuum arc combustion is more complicated.In this paper,on the basis of the existing vacuum arc model,considering the influence of cathode spots of vacuum arc,established a three-dimensional vacuum strip cathode spots of small current vacuum arc physical model,and according to the three basic equations of fluid mechanics,mass conservation equation,momentum equation and energy conservation equation,combined with the maxwell’s equations,the generalized ohm’s law and magnetic diffusion equation established a small current vacuum arc double temperature control equations of MHD model.By using simulation software COMSOL vacuum area of physical model is established and simulation,observe the number of plasma density and electron temperature and ion temperature,pressure,speed,energy flow density,vertical distribution of current density and toroidal magnetic field.Then,the changes of these parameters in the case of electrode rotation are analyzed.The simulation results show that: with the increase of electrode rotation speed,the longitudinal current density distribution is more uniform,the maximum values of electron temperature and ion temperature both decrease,and the energy flow density decreases and the distribution is more uniform.The article also analyzed the electrode rotation effect on the anode thermal process,use the description method of porous media on solid-liquid mixture section,aiming at the condition of the anode surface melting,evaporation is established physical model of phase change process,and use the three basic equations of fluid mechanics combining with the equation of phase transformation on the anode in the process of thermal control system of equations,based on the numerical simulation results of arc plasma anode surface heat flux boundary condition,numerical simulation of the anode surface thermal process.The simulation results show that the surface temperature of the anode contact increases and melts with the continuous inflow of the anode surface energy stream.With the increase of the motor speed,the range of energy flow is larger,the maximum temperature of the anode surface decreases gradually and the distribution is more uniform,and the depth of the molten pool also decreases gradually.