Fluctuation of arc plasma in arc plasma torch with multiple cathodes*

Abstract

Fluctuation phenomena commonly exist in arc plasmas, limiting the application of this technology. In this paper, we report an investigation of fluctuations of arc plasmas in an arc plasma torch with multiple cathodes. Time-resolved images of the plasma column and anode arc roots are captured. Variations of the arc voltage, plasma column diameter, and pressure are also revealed. The results indicate that two well-separated fluctuations exist in the arc plasma torch. One is the high-frequency fluctuation (of several thousand Hz), which arises from transferring of the anode arc root. The other is the low-frequency fluctuation (of several hundred Hz), which may come from the pressure variation in the arc plasma torch. Initial analysis reveals that as the gas flow rate changes, the low-frequency fluctuation shows a similar variation trend with the Helmholtz oscillation. This oscillation leads to the shrinking and expanding of the plasma column. As a result, the arc voltage shows a sinusoidal fluctuation.

Drift characteristics and the multi-field coupling stress mechanism of the pantograph-catenary arc under low air pressure

“…As a sliding electrical contact material, carbon-copper electrodes have high current transmission efficiency, low contact resistance, and excellent crocking resistance, as they are widely implemented in many fields, such as rail transportation and aerospace. [1][2][3][4][5] A carbon-copper electrode is the core element of a pantograph-catenary sliding electrical contact system in the field of rail transit, and it is also subjected to vibration impact, which leads to the arcing phenomenon occurring frequently. According to statistics, the fault caused by pantograph-catenary arcs is the main factor that threatens the power supply's safety, and the loss is very serious.…”