Radial temperature measurements of alternating current arcs

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Abstract
Using the shock-wave technique, measurements of the radial distribution of gas temperature of free-burning alternating current arc columns have been determined. Temperature distributions have been determined at different times in the current cycle for arcs of 8 to 25 A r.m.s. The results show that at any point in the arc column the temperature has a mean value on which is superimposed an oscillatory component having a phase and amplitude dependent upon the spatial position. The alternating current arc exhibits, therefore, a cyclic heat-wave phenomenon. From the variations of phase and amplitude of temperature oscillation, thermal diffusivity values have been deduced. The results show that the a.c. arc has a lower temperature, lower conductance and greater power dissipation than the comparable d.c. arc. Consideration indicates that these effects result from the cyclic radial gas flow generated by the oscillatory nature of the discharge.