The current-voltage characteristics and the electrode heat losses have been measured in a gas-stabilized DC arc generated in a non-transferred arc plasma torch operating on a mixture of argon and nitrogen. The applicability of a Nottingham-type relation between voltage and current to these arcs has been examined by correlating the measured electrode heat losses, plasma power and arc current under different flow rates and gas mixture ratios. The analysis has yielded the Nottingham coefficients which are used to estimate the arc voltage drop. The near constancy of the electrode heat loss per unit current has led to the implication that in stabilized arcs electrode heat loss is linear in current in the limit of small radiation/convection terms. In such cases the first Nottingham coefficient has been found to represent the electrode drop of potential. Secondly, in a nitrogen-argon mixed gas regime, when nitrogen flow rates are more than 20% of argon flow rates, one observes a saturation behaviour in the electrode drop of potential. Beyond this threshold, argon makes a negligible contribution to the arc electrical characteristics.
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