Measurement and calculation of arc power and heat transfer efficiency in pulsed gas metal arc welding

This study investigates the heat transfer efficiency of the pulsed gas metal arc welding (GMAW-P) process. The arc power and heat input were calculated from arc current and voltage measurements and the heat input was also measured with a liquid nitrogen calorimeter. The measured heat transfer efficiency for GMAW-P varied slightly over a wide range of pulse parameters, with an average value of 70%, a maximum of 72% and a minimum of 68%. Welding heat transfer efficiency based on arc power calculated as the product of average current and voltage was too high (averaging 82%), while that calculated using the product of the root mean square (RMS) of the average current and voltage was too low (averaging 61%). Both also varied significantly with pulsing parameters. Mathematical analysis shows that average instantaneous power values must be used when current and voltage vary significantly with time. The experimental differences between the average instantaneous power and the other calculated values are explained by the relative phases of the pulsed current, voltage and arc resistance wave forms.