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I am trying to figure the new wattage? Answered

hello, I built the ark welder from this instructable found athttps://www.instructables.com/id/Build-a-Microwave-Transformer-Homemade-Welder/
I'm trying to figure the new wattage I have two transformers
1: 650 watt MOT-primary at 120 volts 60 Hz 5.41 amps
secondary at 16.5 volts 39.36amps
2: 600 watt MOT primary @ 120v  60Hz  5 amps
secondary @ 16.5 volts 36 amps
the primaries are wired in parallel in the secondaries are in series. The secondaries test at 33 V and I'm guessing roughly 76 amps. I want to calculate the wattage. Is the wattage calculator from the voltage on the primaries (120+120)*76 or calculated from the voltage on the secondaries (16.5+16.5)*76 or am I a complete moron? Also the primaries are parallel are they both 120 V or are they 60 V each thanks in advance.



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Best Answer 9 years ago

Wattage will be primary wattage - losses = secondary wattage. Watts are always volts*amps.

The primaries in parallel (add amps) are drawing 120 * (5.4 + 5.0) = 1248 watts.

Your secondaries in series will add voltage, and current will remain the same; so you'll get (16.5+16.5v) at about 37 amps. 16.5*2*37 = 1221 watts...ish

Remember, your OPEN CIRCUIT transformer will show higher voltage than when under load, so 33 volts is probably a high number.


9 years ago

Secondaries in series. You want to limit the current draw to 36 amps.
Any more amps and you risk slowly overheating #2 MOT.

follard is correct about voltages adding is series and open circuit situations.