--Previous Message-- : http://www.youtube.com/watch?v=3uPxVtUCsfM : : Hi Bert, : I believe that this is the link! Holy Moly! That arc is racing by! Now we : know what a Jacobs ladder looks like when there are several hundred amps : behind it!!! : Fred : Hi Fred,
Here's a clip you might also enjoy from Germany. It uses 3kV at about 500A to create a rotating "jacobs ladder" between two circular metal rails. The rails have a slit so that they are not continuous (to prevent arc forces from otherwise being balanced about half way through the loop). The higher the fault current, the stronger the Lorentz forces, and the more rapidly the arc travels.
This effect is actually put to good use within some high current HV vacuum contactors that need to safely interrupt extremely high fault currents. When the contacts part, magnetic forces cause the roots of the vacuum arc (i.e., the very hot cathode and anode spots) to rapidly sweep across the electrodes in a circular path instead of staying in one place. Rotating the high current arc helps to extend the life of the electrodes by reducing electrode evaporation. The switch would rapidly fail if the arc stayed in one place for any appreciable length of time.
In this clip, it looks like they are actually tapping power right off a pair of phases in a small substation! I really can't see any power company in the US letting someone do a "demo" like this - too much risk for equipment damage. Anyway, here's the URL: