Arc root commutation from moving contacts in low voltage devices

This paper focus on the arc commutation from a moving contact and in partic ular on the anode motion of a high current arc in low voltage current limit ing circuit breakers. Recent investigations have observed that the anode ar e root motion is affected by are chamber geometry. It was previously assume d that cathode root motion was the dominant process. The study uses a flexi ble test apparatus with a solid state high speed imaging system. The experi mental results presented show the influence of are chamber venting, current level, current polarity and contact velocity on are motion. Particular emp hasis is made to the anode motion. The physical process occurring in the an ode root are discussed and related to the observed motion. The results show that the anode root is retarded at the tip of the moving contact and that this is primarily related to the venting process in the are chamber.