I recently bought a older big Miller mig machine with millermatic wirefeeder that came out of a manufacturing plant. Its not been used a whole lot and runs great. On three phase power which is where my problem lies. The price I paid made it well worth the purchase, even if I were to just scrap the copper. But I only have single phase power and would much rather use it.

1. 3 Phase Transformer Sizes
2. Welding Transformer Design-calculation

I need to know the RIGHT procedure to convert it from 3 phase to single phase.I know this will probably loose some duty cycle but that is ok since I'll only use it for general fabrication. I know there are phase convergers but didn't know if that was the best way. Directory list & print. Thanks for the help!

Rotary ConvertersNot to diss Cruiser as he is one of the best resources on this forum, but from what I have read the rotary phase converter is the way to go. You don't even have to keep the single phase motor powered once you get the three phase up to speed. The only thing is you need to have a big enough 3 phase motor to supply the current required for the welder. A better option than the single phase motor is to use a capacitive starting unit. There are many new units available from Ebay stores that have the necessary relays and starter capacitors to do a proper conversion available for nearly HP of motor.

A digital converter as Cruiser calls it (solid state) uses only a capacitor array to generate the third phase and have to be closely matched to the load, which we all know varies with the load on the welder. Check out this link.I have read of many weld shops that have used rotary phase converters with 100% success.Caddi.

3 Phase Transformer Sizes

Welding Transformers are used in machines to change alternating current from the power line into a low-voltage, high amperage current in the secondary winding. A combination of primary and/or secondary taps on the welding transformer are commonly used to provide a macro adjustment of the welding current, as well as adjustment of secondary voltage. Transformer ratings for AC machines are expressed in KVA (kilovolt-amperes) for a specified duty cycle. This duty cycle rating is a thermal rating, and indicates the amount of energy that the transformer can deliver for a stated percentage of a specific time period, usually one minute, without exceeding its temperature rating. The RMS Short Circuit Secondary Current specification indicates the maximum current that can be obtained from the transformer.

Welding Transformer Design-calculation

Since heating is a function of the welding current, this parameter gives an indication of the thickness of the materials that can be welded.For more information read our.