The greenhouse effect of SF6 is a great concern today.The development of highvoltage vacuum circuit breakers becomes more important.The vacuum circuit breaker has mini-mum pollution to the environment.The vacuum interrupter is the key part of a vacuum circuitbreaker.The interrupting characteristics in 'vacuum and arc-controlling techniue are the mainproblems to be solved for a longer gap distance in developing high voltage vacuum interrupters.To understand the vacuum arc characteristics and provide effective technique to control vacuumarc in a long gap distance,the arc mode transition of a cup-type axial magnetic field electrode isobserved by a high-speed charge coupled device (CCD) video camera under different gap distanceswhile the arc voltage and arc current are recorded.The controlling ability of the axial magneticfield on vacuum arc obviously decreases when the gap distance is longer than 40mm.The noisecomponents and mean value of the arc voltage significantly increase.The effective method forcontrolling the vacuum arc characteristics is provided by long gap distances based on the testresults.The test results can be used as a reference to develop high voltage and large capacityvacumn interrupters.
The influence of an arc current on the discharge development and the arc modes ofa single coil type axial magnetic field(AMF)electrode were investigated by a high-speed chargecouple device(CCD)video camera in a long gap distance of 40 ram.The distribution of the axialmagnetic field of the single coil type AMF electrode was computed.By computational results,thesingle coil type AMF electrode could generate higher axial magnetic flux density than the slot typeAMF electrode.It was found that the single coil type AMF electrode could perform better thanthe slot type AMF electrode with the same designing parameters.And the development of the arcmodes experienced diffuse mode,constricted but unstable mode,and constricted and stable modewith the amplitude of the arc current increasing.The correlation between the vacuum arc andthe noise components of arc voltage was investigated too.The interruption capability could beknown in a practical commercial vacuum interrupter by the test results in a demountable vacuuminterrupter(DVC)with a electrode diameter of 50mm and a gap distance of 40mm.The testresults could provide reference to design the high voltage vacuum interrupter adopting the singlecoil type AMF electrode.
Experimental study of the long-gap distance vacuum arc distortion for three typesof axial magnetic field (AMF) contacts, by using high-speed charge coupled device (CCD), ispresented. The arc current was of a half-cycle sine wave with a frequency of 50 Hz, producedby an L-C discharging circuit. The time of appearance and duration of vacuum arc distortionunder three conditions were studied. It was found that the gap distance, current and diameterof the electrode affected the characteristics of vacuum distortion at a long-gap distance. Somecharacteristics of the vacuum arc at a long-gap distance were revealed and the experience anddata for further investigation were provided.
