An advanced interruption method for low-voltage medium-capacity air-break contactors

An advanced interruption method with a unique arc-extinguishing plate has been developed on the basis of a study concerning arc extinction of various electrodes in air. The arc-extinguishing plate has a U-shaped portion that projects toward a contact gap. This arrangement markedly reduces the arcing time and contact wear. The short arcing time is revealed by an electric field analysis for various electrodes and by fundamental experiments concerning the effect of the electrode shape on arc extinction. The reduced contact wear is disclosed by an analysis concerning the influence of arc-immobility time on contact wear. This method has been applied to low-voltage contactors of 25, 35, 50, and 65 A frames. It increased the rated operational current for AC3 duty at 660 V by about 50% and reduced the contact wear for AC4 duty at 440 V by about 20%