A METHOD FOR DETERMINATION OF THE LIQUID AND VAPOR QUANTITIES CREATED BY AN ARC IN AIR ON CONTACT ELECTRODES: AN ORIGINAL TEST DEVICE

摘要

An Energy balance is very difficult to establish for contact electrodes submitted to an electric arc. This balance is different for the cathode and the anode and only few attempts have been made up to now. In order to tackle this problem more precisely, an important step consists in evaluation of the energy transferred to the electrodes, based on the measurement of the liquid and vapor quantities created by the arc. So, we designed an original test device which allowed us to measure directly the amount of liquid and vapor generated. This device consists in mounting two electrodes in the bottom of a rotating vessel so that the liquid created by the arc is completely ejected by the centrifugal force. The gap between the electrodes is kept constant and the arc is triggered by application of a high voltage pulse. The current is nearly a half sinusoidal wave with a peak intensity in the range 100-3000 A and an half period in the range of 1-20 ms. Materials such as Ag, Cu, AgMeO and CuMeO are compared. This experiment has shown great discrepancies between pure materials and composite ones and also between anode and cathode. For example, an Ag anode is 250 times more "eroded" than a Ag cathode. The measurements are compared with the results of a thermal bidimensional numerical model, which finally allowed us to deduce a good approximation for the power density transferred by the arc root to the electrodes.