Effects of arc during mechanical bounces on contact material for different power supply frequencies
Résumé
During a make operation in an electromechanical switching device, an electrical arc could occur because of mechanical bounces and can cause serious damages, such as contact welding and electrodes erosion. The characteristics of this arc are influenced by several parameters such as the level of voltage and current, the load of circuit, the nature of contact materials and, a parameter that we will focus on, the voltage frequency. Indeed, for frequencies equal or greater than 50 Hz, the current can go through zero several times during typical mechanical bounce. The energy transferred to the electrodes, which will condition the welding, depends on the total arc duration, and so on the reignition of the arc. In order to investigate this phenomenon, the contacts welding in relation with the re-ignition of arc have then been studied for different frequencies. The make tests were done for 115 Vrms/750 Arms with a mechanical bounce of 2 ms, with different frequencies 50 Hz/ 400 Hz/ 500 Hz and with AgSnO2 contact material and silver contacts as reference. The welding characteristics, such as welding occurrence and force were measured as a function of arc characteristics (voltage/current/energy). Finally, this investigation showed the importance of the voltage frequency on contactors reliability.
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