Some characteristics of Pd electrical contacts mounted on relays that make and break a dc 30‐v, 10‐a resistive circuit

Abstract

AbstractA description of some of the measured characteristics of palladium switching contacts mounted on miniature relays is presented.For 100,000 switching operations of Pd contacts in the dc 30‐V, 10‐A resistive circuit, we measure the duration of each closing and opening are at each switching, the contact resistance at each closure, the temperature of supporting arm nearby the stationary contact, the number of bouncing at each closure, and the number of switching actions with normal switching functions. Then we compare the data with those data on Ag, AgCdO12 wt% and AgSnO29.3 wt% contacts.On contacts with duty‐making current, closing‐arc duration is very short and the amount of metal transfer is very small. On contacts with duty‐breaking current and those with both making and breaking duty, the large amounts of metal transfer that result will create a large pip and a deep crater on each contact pair.These large pips, deep craters, and the palladium oxide of true contact area influenced greatly each characteristic. Therefore, an obvious difference did not appear between each characteristic in nonpunched contacts and those in punched contacts.After several thousand switching operations, the real contact area consists of a large pip and a crater with a whitish surface; this contact area is made by metal transfer and is made of palladium oxide. It is discussed here that these large oxidized palladium pips and craters influence greatly arc duration, contact resistance, contact sticking, and shortening of the closing‐arc duration simultaneously with an increase in the number of switching operations.