A new approach to suppress arcing in current interruption

Abstract

In an existing circuit breaker, mechanical relay, contactor, or switchgear, almost 100% of the interruption energy is consumed by arcing during a current interruption. A new approach to suppress arc is to convert up to 100% interruption energy into thermal energy with a positive temperature coefficient resistivity (PTC) material. The PTC material could be doped-BaTiO/sub 3/-ceramics, conductive polymer, or metallic PTC element. A computer simulation was conducted to guide a short circuit experiment of a circuit breaker prototype. In the prototype a PTC tungsten wire was connected in parallel with a first pair of contacts but in series with a second pair contacts. During a short circuit interruption in the experiment, the first pair contacts was opened first by an insulating wedge. The arc was suppressed and extinguished quickly around the first pair contacts. The current was then shunted to the tungsten and the second contacts. The tungsten limited the current and dissipated most of the energy. The second contacts finally interrupted the current within the first half cycle. Simulations and tests were completed at single phase circuit levels of 138 V/100 kA and 284 V/100 kA. Results indicate that 80% interruption energy was consumed by the tungsten and only 20% the energy by arcing.