The influence of arc chamber wall material on arc gap dielectricrecovery voltage

摘要

The dielectric breakdown strength of an arcing contact gap aftercurrent zero was compared when using alumina, polyamide 6/6 (PA 6/6),and polyoxymethylene (POM) arc chamber wall materials. Plasmacharacteristics were obtained for each material by applying a reverserecovery voltage across the open contacts at a predetermined delay timeafter current zero. Ablation from each type of chamber wall materialproduced different plasma compositions, each with different recoveryvoltage, arc voltage, and pressure characteristics. Tests were performedfor an arcing current of 12 kA_p for one half-cycle usingsymmetric AgW contacts. A thermal breakdown model along with anexponential curve fit to the measured results were used to obtain theinitial hold-off voltage and plasma time constant for each material. PA6/6 was the better arc chamber gassing material because of its fastertime constant. Two types of breakdown mechanisms were identified:thermal and dielectric