Fundamental characteristics of arc extinction by magnetic blow-out at DC voltages (<500V)

Various DC power supply systems such as photovoltaic power generation, fuel cell etc. have become gradually popular. Under such circumstances switches for electric appliances have to interrupt DC current in DC power systems (for example, DC 300-400V) DC current is much more difficult to be interrupted than AC current which has current-zero, so magnetic blow-out is usually used to extinguish arc discharge. In this paper a model switch is developed with three levels of magnetic blow-out, and gap width and arc length at arc extinction are obtained by a high-speed camera in range of current less than 5 A and voltage lower than 500V. These results are compared with those without magnetic blow-out and the followings can be made clear. When the contacts open, the gap width and arc length at extinction are much shorter than those without magnetic blow-out. As the interrupted current increases, the gap width at arc extinction approaches almost the same value, which is independent of source voltage and separation velocity. However, the arc length at extinction has a minimum value in case of source voltages of 300 and 500V, while the arc length becomes longer with interrupted current increase in case of source voltage of 100V.