Observation of arc-emitted light between slowly opening electrical contacts using a high-speed camera

Relationships between the arc-emitted light and the arc voltage V_arc and current I_arc of breaking arcs at slowly opening Ag or Cu electrical contact pairs are investigated. Electrical contacts are separated at constant speed 1.0 cm/s. In DC 56 V/7 A resistive circuit, the images of the arc-emitted light of breaking arcs are observed with a high-speed camera (1000 frames/s), and the time evolutions of the arc voltage V_arc and current I_arc are measured, simultaneously. As results, it is shown that the increase of the brightness of the arc-emitted light synchronizes with the increase of arc current in the latter half of arc duration. Furthermore, the changes of the effective resistance of the arc discharge (R_arc=V_arc/I_arc) and the input power (P_arc=V_arcI_arc) to the arc discharge are compared with the changing of the brightness of the arc discharge. When the brightness of the arc-emitted light increases, the effective resistance R_arc decreases, and the input power P_arc increases up to the maximum value 97 W that is determined by an experimental circuit.