Experimental study on the characteristics of negative-corona trichel pulses in air

In order to obtain some characteristics of Trichel pulses, we experimentally investigated negative corona in air using a needle-to-plate electrode. We measured the frequency, current, and discharge voltage of Trichel pulses using digital oscilloscope, and average discharge current using micro-amperemeter. Through connecting capacitance in parallel to the discharge structure, we also investigated the influence of external capacitance on the discharge. The results show that the negative-corona Trichel pulses are stable and regular: their pulse frequency increases linearly with averaged current with a speed influenced by the tip radius of needle node, but it is barely influenced by the gap length, the air pressure, and the capacitance in parallel. The pulses also have the same current waveform under different conditions: their rising time hardly changes with the averaged current, the gap length, the air pressure, the tip radius, or the capacitance, and their amplitude is influenced slightly by the averaged current as well as the other discharge conditions. It is concluded that Trichel pulses are characteristic discharge in corona region, and with a given electrode pair, their generation process is independent of discharge current, gas pressure, and external circuit.