Patent ID: 7615720

Claim:
A contact start plasma arc system, comprising: a torch body; an electrode having a longitudinally disposed axis and mounted in the body; a nozzle having a longitudinally disposed axis, the nozzle axis being disposed substantially collinearly with the electrode axis; a power supply coupled to the electrode, the nozzle and a workpiece, the power supply providing a current for operating the torch in a pilot arc mode and a transferred arc mode; and a passive pilot arc circuit coupled between the power supply and the nozzle, wherein the pilot arc circuit controls the operation of the torch in the pilot arc mode and automatically disconnects power to the pilot arc mode to facilitate an automatic transfer from the pilot arc mode to the transferred arc mode by reducing a pilot current towards zero as a pilot capacitor in the pilot arc circuit becomes more charged. such that the pilot arc circuit opens and the pilot current stops flowing through the pilot arc circuit when the pilot capacitor becomes essentially fully charged.