A simple theory

based on a two-zone approximation of the arc column

has been developed to study the properties of arc generated by the air plasma cutting process. Theoretical results of arc radius

arc voltage and the pressure at the nozzle exit as a function of arc current have been obtained for a range of operating conditions

including varying air flow rates

and different nozzle diameters. Some results obtained are in good agreement with the measured values for an air plasma cutting. Also

the dependence of the nozzle diameters and the mass flow rate of plasma gas on plasma power and arc force has been discussed.