New interruption method for low-voltage, small-capacity, air-break contactors

A novel interruption method that can shorten arcing time and reduce contact wear in contactors having a rated operational current of about 20 A without an arc extinguishing plate is described. In this approach, a slit is formed in the stationary conductor, and an arc runner is located on the slit. The maximum arcing time in a 726 V (660 V*1.1), 74 A circuit is shortened by about 65%, and the contact wear in a 440 V, 80 A circuit is reduced by 21%. This method produces enough magnetic flux density to drive an arc, and the shortening of the maximum arcing time and the reduction of the contact wear are attributed to the electromagnetic drive of the arc. This method has been applied to contacts of 18 A and 21 A frames; it increased their rated operational current for AC3 duty at 660 V by 50%.<
>