The Current Level to Weld Closed Contacts

A model is developed to determine the peak current required to weld closed contacts. The model considers: (1) the total contact resistance of the closed contacts by including the expected constriction resistance as well as the resistance resulting from the high temperature of the contact spot; (2) the effect of the 'blow-off' force from the passage of the current through the contact spot; and (3) the reduction of the hardness of the contact metal in the vicinity of the high temperature at the contact spot. In general the model predicts the values found from experiment within the uncertainty of the material data given in the usual contact materials data tables.