Experimental investigation on the blow open force of low voltage electric apparatus

Blow open force has important effect on the motion status of the moving contact after it separates from the static one, and which affects the performance of low voltage electric apparatus. To one double-breaker model, measuring the arc current, voltage and force acting on the moving conductor and calculating the elector-dynamic repulsion force of the conductor loop with 3-D finite element method, the characteristics of blow open force have been investigated under the conditions of 3-6 kA prospective short circuit current and 2-6 mm contact gap with the influence of gassing material and venting size. It demonstrates that the ratio between the emerging blow open force and arc power F_B/ui decreases with the arcing time, the contact gap has less effect on F_B/ui and the characteristics of the blow open force are similar when the peak value of the short circuit current is beyond 4 kA. In addition, the value of the blow open force will increase with the existence of gassing material in arc chamber as well as the increase of the venting.