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3phase to single phase conversion with transformer for equal line currents
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ZeroResistance:

--- Quote from: tautech on July 22, 2018, 07:15:17 am ---OK, so have you monitored current draw or mains voltage sag when spot welding ?
How many amp supply is your single phase outlet ?
What mm3 is the outlet supply cable ?

--- End quote ---


--- Quote from: IanB on July 22, 2018, 07:21:06 am ---Firstly, 10 kW should be very possible on a 240 V single phase mains supply. That is only 42 A. Maybe the first thing to investigate is to stiffen up your supply circuit? Have a dedicated circuit from the panel with suitably heavy gauge wire (e.g. 16 mm²) and keep the run as short as possible. Although 10 mm² might technically seem thick enough, it might have too much voltage drop for your application.

--- End quote ---

What both of you are saying makes a lot of sense, I didn't check either of those things when unit was spot welding. Also the socket outlet that I was using is located pretty far away from the main input, and may have had 2.5mm2 wiring. I could just see the lights diming off when the unit was spot welding.
ZeroResistance:

--- Quote from: sibeen on July 22, 2018, 07:01:47 am ---The problem with the Scott, or Leblanc, is that they are 3 to 2 phase connections and the two phases are 90 degrees apart. You can load up just one of the output phases but the input currents will no longer be balanced.

I thought I had a mathcad document lying around on the computer where I had to calculate all the currents for a proposed job, and how the current balancing would work out under different scenarios.  The job never came off and now I cannot locate the file.

--- End quote ---

Currently I am planning to go in for a 2 phase system, I won't bother with the unbalanced current for now. So 10Kw on single phase is around 40Amps. Will this be distributed in a 2 phase system where each phase will draw  20Amps. Is a 2phase + 1 Neutral system a better idea?
tautech:

--- Quote from: ZeroResistance on July 22, 2018, 09:11:31 am ---
--- Quote from: tautech on July 22, 2018, 07:15:17 am ---OK, so have you monitored current draw or mains voltage sag when spot welding ?
How many amp supply is your single phase outlet ?
What mm3 is the outlet supply cable ?

--- End quote ---


--- Quote from: IanB on July 22, 2018, 07:21:06 am ---Firstly, 10 kW should be very possible on a 240 V single phase mains supply. That is only 42 A. Maybe the first thing to investigate is to stiffen up your supply circuit? Have a dedicated circuit from the panel with suitably heavy gauge wire (e.g. 16 mm²) and keep the run as short as possible. Although 10 mm² might technically seem thick enough, it might have too much voltage drop for your application.

--- End quote ---

What both of you are saying makes a lot of sense, I didn't check either of those things when unit was spot welding. Also the socket outlet that I was using is located pretty far away from the main input, and may have had 2.5mm2 wiring. I could just see the lights diming off when the unit was spot welding.

--- End quote ---
As some example.....years ago before our overhead lines were up-rated, the best/strongest socket in a house was the one on the oven as normally they were fed with 6mm3 cable then just short sections of 2.5mm3 to the outlet. Simply it was like being plugged straight into the switchboard.

Even now we see certain times of the day that power levels are poor and that's more noticeable on single phase than 3. When I had only a single phase welder, sometimes it was better to just postpone a job than struggle with a weak welder due to low power. Now I've got 3ph and 400A I can just wind more on and dish it out !  >:D
hussamaldean:
IMO, the best way to do it is using three phase full bridge rectifier then an inverter to converter it back to AC. however, there is IGBT DC welding machine which can provide better performance compared to old technology.
regards
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