Q&A: Can a stepdown transformer be used as a stepup transformer?

Can a stepdown transformer be used as a stepup transformer? Can a 440 single phase welder run on 220? If you have a transformer that inputs 440 and outputs 220, can it just be wired backwards? Generally, yes, but there may be some losses. The transformer should be capable of maintaining the KVA rating though. Remember that the current at 220 is twice that of the current at 440.

Often times the 440 side is rated (for instance) 30 amps with the 220 side being rated at 60 out. So the wiring may..may be smaller in diameter on the 440 side. So if you reverse it to step up and try to draw 50 amps on the 440 side (really really really big welder), you may harm it.