THE EFFECT OF CONTACT OPENING VELOCITY AND THE MOMENT OF CONTACT OPENING ON THE AC EROSION OF AG CDO CONTACTS/

This paper presents experimental results on the influence of contact o pening velocity and the moment of contact opening with respect to the start of the ac current cycle on arc energy and contact erosion when b reaking an ac resistive circuit. The test currents are 5.6 A, 14.7 A, and 26.3 A, and the contact material is Ag/CdO (90/10). A computer con trolled test system allows the control of the contact velocity profile s with constant velocities up to 0.8 m/s and also enables the synchron ization of the contact opening with a point on the ac current waveform . Contact erosion is evaluated by measuring the mass changes of the ca thode and anode. The results show that increasing the contact velocity from 0.1 m/s to 0.8 m/s leads to an increase in the arc energy. The m aterial transfer from one electrode to another is shown to depend on t he current, the polarity of the moving contact, the moment of the cont act opening with respect to the start of the ac current cycle, and the opening velocity of the contacts.