A study on estimation of arc parameters for low voltage DC arc breaking process

We aim at constructing a DC arc black-box model. As a first step, in this paper, DC breaking experiments were carried out. The arc-quenching device is connected in series with resistance R, inductor L, switch S, and DC source of E=120 V. The interruption tests were conducted for three cases of DC current, IDC of 5 A, 15 A, and 20 A, under the circuit conditions without L and with L=3.3 mH and 6.6 mH. Arc parameter sets were estimated by using the Mayr's equation. In Mayr's equation. θ [s] and N0 [W/mm] are called the arc time constant and arc power loss, respectively. Assuming that the product of θ and N0, Q=θN0 [J/mm], was constant, the time variations in θ and N0 for various magnitude of Q were estimated from the measured arc voltage and current waveforms by iterative calculation so that the resistance of the arc column per unit length obtained from the Mayr equation agreed with the measured one. The dependence of the arc parameter on the corresponding instantaneous current was investigated under the condition in which the inter-electrode distance is more than 5 mm, because the arc column was considered to be unstable in the inter-electrode distance less than 5 mm. As a result, it was found out that the arc parameters derived under different experimental conditions might be expressed with one function of the transient arc current.