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

An interruption method for low-voltage, small-capacity, air-break contactors is developed. The features of the construction of this method are that a slit is formed in the stationary conductor with a contact, and an arc runner is located on the slit. The operation, construction, experimental conditions and results, and applications of the method are discussed. The method shortens the maximum arcing time in a 726 V, 74 A circuit by about 70% and reduces contact wear in a 440 V, 80 A circuit by 21%, compared with the conventional method. This method produces enough magnetic flux density to drive an arc. The shortening of the maximum arcing time and reduction of the contact wear are considered to be due to the electromagnetic drive of the arc. This method has been applied to contactors of 18 A and 21 A frames; it increased their rated operational current for AC3 duty at 660 V by 50%.<
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