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

Abstract

A 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.

Contacts materials performances under break arc in automotive applications

“…If the depth of the crater exceeds the thickness of the rivet, good contact conductivity can no longer be assured. Furthermore locking of the pip on the crater may fail to open the contacts, especially in weak opening force range [22]. On Fig.…”

Comparison of some characteristics of contact resistances on four kinds of Ag‐Pd alloy contacts with frequent switching of a 30V, 10A DC resistive circuit

“…By many iterations of switching operations, the damage to the contact surface by switching arc and the deposits of film and polymers [6,7,[9][10][11] become visible. Therefore, the average contact resistance after 100 initial switching operations that are considered to have little effect is shown in Fig.…”