Aging Characteristics of Contact Electrodes of Low Voltage DC Switches

With the present state of the direct current (DC) distribution market, securing the safety of the DC distribution system is emerging as a major issue. Like AC distribution systems, DC switches and circuit breakers are one of the main means to ensure safety. However, in the DC system, since there is no current zero point in the load current, the phenomenon occurring when the circuit is cut off is different from that of the AC system, so technical research is required to cope with this. In this study, the aging characteristics of the contact electrode of a 400 V class low voltage DC (LVDC) switch is studied for the development of wall-mount switches or circuit breakers for residential houses. As an arc extinguishing method to break DC load current, a prototype experimental circuit breaker that uses a magnetic extinguishing method that is effective for blocking low voltage low power DC is invented, and an automated experiment system is established. The DC switch test repeats the operation of turning it on and off 13,000 times, and continuously evaluates the performance of the electric contacts by calculating the voltage drop between the electrode contacts and the corresponding Ohmic resistance value when conducting every 500 times. This paper tests six contact materials to compare the aging characteristics of them by evaluating contact resistance during the test period. AW18-Cu composite material showed the most stable and excellent contact performance for LVDC switches during the entire test operation period.