Some geometrical and electrical aspects on the wire-to-cylinder corona discharge

Corona discharge is a gas discharge that can be applied in a vast number of industrial applications. In all of them, knowing the current-voltage curves (CVCs) is of high importance because they determine the corona discharge operation range, from the inception voltage to the breakdown voltage. The CVCs are influenced by geometrical factors, ambient conditions and electrical parameters so the one only way to increase operation range without achieving spark voltage is lowering the inception voltage. Regarding geometrical parameters, it is widely known that reducing the distance between electrodes decreases the inception voltage, however two behaviours are found for the emitter radius in the literature. One of them establishes that there is a limit to the emitter size from which there is no change in the CVCs, while the another theory states that by reducing the emitter radius there is always an increase in the corona current. A series of measurements were carried-out for wire-to-cylinder corona discharge in parallel arrangement to study the influence of geometrical and electrical parameters over the current-voltage curves, mainly focusing in the wire radius. The results show that reducing the emitter radius always produces an increase in the corona discharge current. Although the inception voltage is generally higher for positive than for negative polarity, the experimental data suggest that there is an emitter radius from which this trend changes, being the negative inception voltage larger than for positive i.e. the inception voltage depends on the polarity of the discharge and the wire radius. Furthermore, the determination of the inception voltage by using four formulae is compared with the experimental data due to its importance to establish the operation range of corona devices. The influence of geometrical parameters is especially relevant to design and manufacture corona discharge devices e.g. low noise and without moving parts flying systems.