1996 Volume 14 Issue 1 Pages 108-115
In order to improve the sensitivity and reliability of the arc sensor, it is necessary to know how its characteristics change with the welding circuit conditions and the welding process variables and so on, because the sensor simply uses the electric signals — the weling current and/or the welding voltage as it's outputs. The present work has theoretically analyzed these relationships based on the nonlinear and the linearized models of the arc sensor. The analyses were made in time-domain and in frequency-domain. The results have revealed that the welding loop inductance Lw shows a little effects on the characteristics of the arc sensor if the variation frequency (f) of the torch height is lower than about 6 Hz, but its effect becomes greater in higher frequency range and increases with increasing f. The equivalent output resistance Ks (the slope of U-I (voltage-current) characteristic) of welding power supply exhibits greater effect on the characteristics of the arc sensor in full frequency range. The change in compositions of electrode wire or in welding conditions also effects the characteristics of the arc sensor but these effects are small in extent compared with Lw and Ks.
Finally, the real-time behaviour of the arc sensor during the welding for a V-type joint groove was simulated, and the results were discussed by combination of the frequency-characteristics of the arc sensor and real welding conditions. Based on these results, it may be a better selection to use the welding current rather than the voltage as a detected signal in lower frequency range, but it does not necessarily remain good way in high frequency range for current wave-form generally exihibits greater asymetry with respect to the center of groove and current response also normolly declines with increasing f for a conventional welding system.