stick machine question

[cope]

I used to know the answer to this question, but I had a senior moment or two since then. My Miller machine has a low range 20-125 amps AC and a high range 40-250 amps AC. What is the rationale or benefit from running 100 amps on low range rather than high. Seems to me it had something to do with a smoother arc, but I can't remember.

[dseman]

Cope,
By using the lower welding range you are selecting a different tap on the transformer which has a higher OCV, which is helpful in lighting your arc. It also has a steeper volt/amp machine slope. That is, for a given change in arc length (arc voltage), there is a much smaller change in the actual amperage. If this is a thunderbolt, I think the OCV difference is about 15Volts higher (75V vs. 60V).

hope this answers your question,
-dseman

[cope]

Thanks for the reply. Not a Thunderbolt, its a Model 88 made in 1968.