Step 1: Lay one side of a straight edge across the graph at the six cycles of current “one time” point (the left hand vertical scale of the conversion factor chart).
Step 2: Pivot the other end of the straight edge across to line up with the “60 welds per minute” on the far right vertical scale.
Step 3: At the intersection of your straight edge with the diagonal conversion factor scale line, you should be able to read a conversion factor of .32 off the lower 1/2 of the line.
Step 4: Multiply the required current (60,000 amps) by the conversion factor (.32) to get the “continuous duty current” of 19,200 amps. Now proceed to the Water Cooled Jumper Selection Chart to read complete the selection.
Step 5: Line up your straight edge on the 19,200 continuous duty amp mark, and find the intersection with your desired length line (from below, we want 60 inches).
Step 6: Any cable whose line is above this point may be safely used, since the load it would carry will be within its thermal capacity. In our case the 1000 MCM cable would be the best match, and will not exceed the design specifications of the jumper cable.
Example Data:
6 cycles of current “on time” per weld
60 welds per minute
60,000 amps per weld
5 ft cable Length |