As the main source of the vacuum arc plasma,cathode spots(CSs)play an important role on the behaviors of the vacuum arc.Their characteristics are affected by many factors,especially by the magnetic field.In this paper...As the main source of the vacuum arc plasma,cathode spots(CSs)play an important role on the behaviors of the vacuum arc.Their characteristics are affected by many factors,especially by the magnetic field.In this paper,the characteristics of the plasma jet from a single CS in vacuum arc under external axial magnetic field(AMF)are studied.A multi-species magneto-hydro-dynamic(MHD)model is established to describe the vacuum arc.The anode temperature is calculated by the anode activity model based on the energy flux obtained from the MHD model.The simulation results indicate that the external AMF has a significant effect on the characteristic of the plasma jet.When the external AMF is high enough,a bright spot appears on the anode surface.This is because with a higher AMF,the contraction of the diffused arc becomes more obvious,leading to a higher energy flux to the anode and thus a higher anode temperature.Then more secondary plasma can be generated near the anode,and the brightness of the‘anode spot’increases.During this process,the arc appearance gradually changes from a cone to a dumbbell shape.In this condition,the arc is in the diffuse mode.The appearance of the plasma jet calculated in the model is consistent with the experimental results.展开更多
Results observed experimentally are presented, about the DC arc plasma jets and their arc-root behaviour generated at reduced gas pressure without or with an applied magnetic field. Pure argon, argon-hydrogen or argon...Results observed experimentally are presented, about the DC arc plasma jets and their arc-root behaviour generated at reduced gas pressure without or with an applied magnetic field. Pure argon, argon-hydrogen or argon-nitrogen mixture was used as the plasma-forming gas. A specially designed copper mirror was used for a better observation of the arc-root behaviour on the anode surface of the DC non-transferred arc plasma torch. It was found that in the cases without an applied magnetic field, the laminar plasma jets were stable and approximately axisymmetrical. The arc-root attachment on the anode surface was completely diffusive when argon was used as the plasma-forming gas, while the arc-root attachment often became constrictive when hydrogen or nitrogen was added into the argon. As an external magnetic field was applied, the arc root tended to rotate along the anode surface of the non-transferred arc plasma torch.展开更多
Investigations are reported into the use of an electromagnetically convoluted arc,external to a magnetic field(B-field)producing coil,in combination with a parallel R,L,C resonant circuit for interrupting quasi-steady...Investigations are reported into the use of an electromagnetically convoluted arc,external to a magnetic field(B-field)producing coil,in combination with a parallel R,L,C resonant circuit for interrupting quasi-steady currents.In order to elucidate the complex interactions between the arc,B-field and R,L,C circuit,the B-field producing coil is energised independently from the current to be interrupted and the R,L,C circuit.Experimental results are presented for the time variation of the currents flowing through the arc gap,the B-field coil and the parallel R,L,C circuit,along with the voltage across the arc gap.An insight is gained into the role of various effects,which are produced by the complex interactions and which might be used to advantage for direct current interruption.展开更多
基金supported by National Natural Science Foundation of China(Nos.U1866202 and 51877164)State Key Laboratory of Electrical Insulation and Power Equipment Fund(No.EIPE19128)。
文摘As the main source of the vacuum arc plasma,cathode spots(CSs)play an important role on the behaviors of the vacuum arc.Their characteristics are affected by many factors,especially by the magnetic field.In this paper,the characteristics of the plasma jet from a single CS in vacuum arc under external axial magnetic field(AMF)are studied.A multi-species magneto-hydro-dynamic(MHD)model is established to describe the vacuum arc.The anode temperature is calculated by the anode activity model based on the energy flux obtained from the MHD model.The simulation results indicate that the external AMF has a significant effect on the characteristic of the plasma jet.When the external AMF is high enough,a bright spot appears on the anode surface.This is because with a higher AMF,the contraction of the diffused arc becomes more obvious,leading to a higher energy flux to the anode and thus a higher anode temperature.Then more secondary plasma can be generated near the anode,and the brightness of the‘anode spot’increases.During this process,the arc appearance gradually changes from a cone to a dumbbell shape.In this condition,the arc is in the diffuse mode.The appearance of the plasma jet calculated in the model is consistent with the experimental results.
基金the National Natural Science Foundation of China(Nos.10575127,50336010)
文摘Results observed experimentally are presented, about the DC arc plasma jets and their arc-root behaviour generated at reduced gas pressure without or with an applied magnetic field. Pure argon, argon-hydrogen or argon-nitrogen mixture was used as the plasma-forming gas. A specially designed copper mirror was used for a better observation of the arc-root behaviour on the anode surface of the DC non-transferred arc plasma torch. It was found that in the cases without an applied magnetic field, the laminar plasma jets were stable and approximately axisymmetrical. The arc-root attachment on the anode surface was completely diffusive when argon was used as the plasma-forming gas, while the arc-root attachment often became constrictive when hydrogen or nitrogen was added into the argon. As an external magnetic field was applied, the arc root tended to rotate along the anode surface of the non-transferred arc plasma torch.
文摘Investigations are reported into the use of an electromagnetically convoluted arc,external to a magnetic field(B-field)producing coil,in combination with a parallel R,L,C resonant circuit for interrupting quasi-steady currents.In order to elucidate the complex interactions between the arc,B-field and R,L,C circuit,the B-field producing coil is energised independently from the current to be interrupted and the R,L,C circuit.Experimental results are presented for the time variation of the currents flowing through the arc gap,the B-field coil and the parallel R,L,C circuit,along with the voltage across the arc gap.An insight is gained into the role of various effects,which are produced by the complex interactions and which might be used to advantage for direct current interruption.
