Power circuit apparatus for starting and operating plasma arc

An apparatus for starting and maintaining a plasma arc which is characterized by the use of a power supply of relatively low capacity and cost, and comprising

• a plasma torch comprising a rear electrode composed of a tubular metal member having a closed inner end and an open outer end, a front tubular metal member having a bore therethrough and mounted in coaxial alignment with and separated from said open outer end of said rear electrode, and gas vortex generating means disposed intermediate said rear electrode and said front tubular member for generating a vortical flow of a gas therebetween,
• a direct current power supply,
• circuit means operatively interconnecting said power supply to said plasma torch and including a first line connecting one terminal of said power supply to said rear electrode, and a second line connecting the other terminal of said power supply to said front tubular member,
• electrical pulse generator means operatively connected to said circuit means for selectively applying direct current pulses of relatively high energy to said circuit means and which is sufficient to intiate an electrial arc between said rear electrode and said front tubular member, said pulse generator means comprising a source of direct current pulses, and transformer means connecting said source to said first line in series with said plasma torch,
• bypass switch means for selectively removing said transformer means from said circuit means, and
• protective capacitor means disposed in said circuit means in parallel with said power supply for protecting said power supply from the relatively high transient voltage produced by said pulse generator means.