Characteristics of vacuum breakdown field and comparison of field enhancement factor β in CuCr electrodes with slit configuration

A contact electrode of vacuum interrupter (VI) has slit parts on the electrode surface to control the vacuum arc during the current interruption. The edge configuration of the slit is important for the withstand performance of high voltage application for VI. We investigated the effect of the curvature radius of slit's configuration on the field enhancement factor β and the characteristics of vacuum breakdown for the slit electrodes made of CuCr alloy simplified simulating the AMF-electrode. As the results, the round chamfered configuration at the edge of slit increases the breakdown field, because of the reduction of pre-breakdown current flowing, that is, small field emission current. This is due to be small β-value by rounding chamfering of the edge at the slit. The BD field of the slit electrode can be improved by rounding the edge of the end of the slit more than 1 mm curvature radius, and the curvature of 0.5 mm radius for R0.5 slit electrode had almost little effect on improving the BD field owing to manufacturing inadequate curvature at the edge of slit.