Influence of AC interruption points on AC arc erosion of silver based contact materials

This paper presents experimental results obtained from a study into the reduction of contact erosion on break, using controlled AC point interruption principles. Five thousand break tests are carried out for a utilisation category of AC-1, at a current of 6 A rms, a gap-length of 2 mm on AgCdO (90%, 10%), AgCu3 (97%,3%) and Ag (fine, 99.9%) contacts, each with a diameter of 5 mm. The results show that by interrupting the circuit at selected points on the AC waveform, the rate of erosion varies significantly for different contact materials and the fine silver in general loses material. The minimum mass change for AgCdO is at interruption point /spl alpha/=135/spl deg/ and for AgCu3 surprisingly is at /spl alpha/=45/spl deg/. In the random break operation both AgCdO and fine Ag lose materials from both electrodes, but AgCu has an equal amount of material transfer. The paper also discusses the practical benefits of a controlled interruption technique within three-phase switching devices by incorporating a logic sequencer.