Work speed of circular electrode of 220 mm diameter for carrying out seam welding at 4 welds per cm on 1.6 mm thick mild steel tube. Welding cycle consists of 3 cycles ‘on’ and 2 cycles ‘off’ Power supply is at 50 Hz. Calculate R.P.M. and energy requirement of the above circular electrodes assuming effective resistance between electrodes as 100 ohm.

Weld per min = (frequency × 60)/ (cycles for weld + interval cycles)
= (50 × 60)/ (3 + 2) = 600 welds/ min.
Work speed (mm / min) = (welds/ min) / weld required per mm
= 600 / (4/10) = 1500 mm/ min.
Therefore, RPM of electrode = work speed in mm per min/ π × electrode diameter in mm
1500/ (3.14 × 220) = 2.17 rpm.
For 1.6 mm thick M.S. Plate, current requirement is around 10,000 amperes
Therefore, Energy required = I²RT = (10,000²) × 100 × (3/ 50) = 600 Joules.