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 the arc extinction of various electrodes in air. The arc-extinguishing plate has a U-shaped portion which projects toward a contact gap. This arrangement gives a marked shortening of arcing time and a considerable reduction of contact wear. The short arcing time is shown by an electric field analysis for various electrodes and fundamental experiments concerning the effect of the electrode shape on arc extinction. The small contact wear is shown by an analysis of the influence of arc immobility time on contact wear. This method has been applied to low-voltage contactors of 25 A, 35 A, 50 A, and 65 A frames. It increased the rated operational current for AC 3 duty at 660 V by about 50%, and reduced the contact wear by about 20%.<>