An electric welding plant supplies controlled welding output to an electrode and workpiece through a complete return circuit. This illustration shows a stick-welding power source, holder, electrode, workpiece and work-return clamp. The calculator compares an assumed current-squared heating budget and divides an illustrative time window into arc-on and rest portions.
Electric Welding Plant Interactive Calculator
See the electrode and work-return circuit, then compare an illustrative current-squared duty estimate. Arc-on and rest animation follow the calculated fraction.
Equation Used
- Average resistive heating scales as current squared.
- Allowable average heating is assumed constant; estimated duty is capped at 100%.
- No fixed losses, thermal transient, ambient or cooling model.
- Time-window scaling is illustrative and does not establish an operating limit.
Illustrative heating comparison only. Use the actual equipment duty-cycle chart and current range.
The power source and welding circuit
The source supplies the electrode through one cable. The work-return clamp and its separate cable complete the output circuit through the workpiece. The clamp is therefore part of the welding-current path; the drawing does not use the table or an unconnected wire as a substitute.
The arc appears between the electrode tip and the workpiece during the calculated on-portion. During the rest portion it disappears and the holder is shown raised. This is a component illustration: an operator, electrode consumption and travel along a seam are omitted.
The source enclosure is generic. Its internal converter, transformer, cooling system and controls depend on the actual machine. No specific circuit architecture or product current range is inferred from the picture.
Understand the duty comparison
Enter a reference current and duty percentage from a known rating, then a comparison current. The calculator estimates a duty fraction by assuming that allowable average current-squared heating remains constant.
The adjustable time input is an illustrative comparison window. It multiplies the estimated fraction into minutes for visualization. It does not modify the reference equipment’s rated test period or authorize longer uninterrupted operation.
For an actual machine, use its published current range, duty-cycle chart and stated test conditions. Duty ratings are tied to those conditions, and a single reference point does not establish the whole thermal behavior.
An average current-squared heating model
If resistive losses were proportional to I² and allowable average heating were unchanged, Dnew Inew²=Dref Iref². This gives Dnew=Dref(Iref/Inew)², with percentage duty capped at 100%.
For an illustrative window T, arc-on portion is TDnew/100 and the remaining portion is T minus that time. Current/reference current is 100Inew/Iref percent.
This is a conditional approximation, not a full thermal model. Fixed losses, changing resistance, cooling, ambient temperature, semiconductor limits and peak temperature are absent. Averaging the same I² over different periods does not guarantee the same peak temperature.
Compare the default point
A reference of 200 A at 60% duty, compared at 200 A over a 10-minute window, gives 60%, six minutes of arc-on portion and four minutes of rest portion. The animation uses the same 60/40 split.
At 400 A the simplified inverse-square estimate becomes 15%, or 1.5 minutes within that 10-minute illustration. This does not establish that the machine can output 400 A or operate at that duty; its published limits still control.
At 100 A the expression would exceed 100%, so the displayed fraction is capped at 100%. That mathematical cap is not a guarantee of continuous-duty capability.
Limits of the duty estimate
A machine-specific duty-cycle curve describes performance under specified test conditions. A single-point inverse-square calculation cannot establish the complete duty curve.
Many welding manuals illustrate duty over ten minutes; other conditions must be taken from the particular equipment. The freely adjustable comparison window is deliberately separated from such a rating. Increasing it does not establish a longer permissible continuous weld.
This model does not predict cooling time to a particular temperature, thermal-trip operation, electrode selection, weld quality, deposited mass or arc voltage. Equipment ratings and maintenance requirements must come from the particular machine’s documentation.
Electric welding plant questions
Why does the arc turn off partway through the animation?
The arc is visible during the estimated on-portion and switches off during the rest portion.
Can this estimate replace the manufacturer’s duty chart?
No. It is an average I² comparison and omits machine-specific thermal and electrical limits.
Does a 30-minute window allow a longer continuous weld?
No. It only rescales this illustration. Actual duty-cycle ratings apply over their specified periods and conditions.
Is the work-return cable a protective earth?
No. It is the depicted welding-current return path from the workpiece to the output terminal. Protective earthing is a separate function and is not shown.
References
- Miller, PipePro owner’s manual: typical stick-welding connection diagram — power source, electrode holder and separate work-return connection.
- Miller OM-316, Duty Cycle Charts — duty percentage, rated load and ten-minute period. The inverse-square comparison here is a stated approximation, not a replacement for those curves.
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