Tomoya Ito

Growth of Transferred Pip and Electrical Properties of AgCdO Make-Only Contacts in Resistive Circuit with DC 14 V and 42 V Power Supply

AgCdO12wt% contacts mounted on electrical relays were tested in a dc 14V-21 A or 42V-8.4A resistive circuit as make-only contacts. In this experiment, we took photograph records and measured arc duration and number of bounces. A transferred pip was grown on the cathode surface, and its height H grew H/Ga > 0.5, where where H is height of pip, Ga is the contact separation, sticking occurred easily. Neither the rapidity of growth or the shape of the transferred pip influenced circuit conditions, but there were differences observed for the each sample. Since the arc discharge of switching operations at make-only contacts occurs during a rebound, the arc duration, as well as the number of bounces fluctuates.

Observation of Pips Formed on Ag/SnO 2 Contacts in DC14 V-21 A Resistive Circuit

In order to study the growth of transferred pips, we operated Ag/SnO 2 12 wt% contacts mounted on an electromagnetic relay in a DC14V-21 A the resistive circuit as make-only contacts, and took photographs of the transferred pips formed on a cathode surface. In this experiment, the pip shape was different depending on whether the movable contact was the cathode or anode. When the movable contact was the cathode, pip grew high, and became 0.7 mm height at maximum. Sometimes, the pip collapsed. Sticking occurred, when the pip shape became H/Dr ≥ 2.5 and H/Ga ≥ 0.5, where H is pip height, Dr is diameter of pip root, and Go is gap length of open contacts. Judging from this result, we can predict that when a pip grows to H/Dr ≥ 0.5 and H/Ga ≥ 0.5, sticking will easily the occur. When the movable contact was the anode, no tall pip was formed, because of pip breakages. Sticking occurred for three samples although the pips grew to H/Dr ≥ 0.5 and H/Ga ≥ 0.5. In this case we could not obtain a numerical relationship between of the pip shape and the occurrence of sticking.