Lincoln Idealarc R3S-325 to single phase
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  1. #1
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    Default Lincoln Idealarc R3S-325 to single phase

    This is concerning a Lincoln Idealarc R3S-325. Converting to single phase.
    Reading a lot of posts about doing the conversion and finding this utube vid

    Lincoln R3S-325 3ph To Single Phase Conversion w/capacitor - YouTube

    In trying to figure out and wrap my head around this. I found a few online calculators

    1. Calculate RC series circuit
    RC-Series circuit, online calculator

    This one wanted some numbers I had no idea about, the resistance value. So I googled and found the "" Capacitor Impedance Calculator ""

    2. Capacitor Impedance Calculator
    Please Wait... | Cloudflare

    Plugging in different uf spit out different resistance values that I plugged in.

    Of course I didn't do of this before buying a 45uf and 50uf cap. rookie -- I know / I know lol

    Here is the workflow I used.

    I have been playing around on online calculators, using different uf. 1st using a capacitor resistance calculator uf + 60Hz and " for the states" and 2nd inputting that resistance + 220v in the phase shift calculator. The different uf gives the same angle shift 45 ° and 155.56 voltage. But it does change the Currant/Amps, the larger the uf the more amps.

    45uf = 58.9463R = 2.64A
    50uf = 53.0516R = 2.93A
    70uf = 37.894R = 4.11A

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    Adding the 2nd capacitor parallel 45uf + 50uf brings the L3 amp up to 9 amps.

    I haven't been able to find any 400 - 600 uf run capacitors. I really don't want a bank of capacitors rattling inside the welder. I'm wondering if I really need to worry about evening up the L1-2-3 amps, or just leave it with the 50uf. The welder didn't seem to care, using .045 wire and huge chunk of steel didn't seem to slow it down.

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    Yep. I don't think my half assed welding skills will ever tax the machine enough to worry aboot. I really don't need a Ferrari as a grocery getter lol
    If ever a crazy alignment of the planets and George wins the lottery on a Friday to tax the welder, I know how to fix it

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    Taxing it is the wrong way to say it.
    The welder has to wiring options. Below 300v and Above 300v. So the welder isn't loosing power. Just the 3rd leg is a little small and retarded.

    I know and understand all about small and retarded 3rd legs

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    If it works, just use it. Dkamp is the expert on these conversions, with some luck he might chime in with some info. I did the conversion on a Miller some years ago, it had already been converted once into a carbon arc power supply. I could not find any big run caps either, ended up using some Ducati caps from ebay, iirc they were high on the uf scale, but machine works. Looks like they are still available
    Used Ducati Energia (4.16.84.4831) 200 uF / 60 Hz - 450 V - W 29/15 -Capacitors | eBay

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    Thank you dalmatiangirl61 for looking out and digging up the link. I wasn't able to find anything on ebay except motor start caps. My search-Fu wasn't working.

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    So the video doesn't really show much detail about what he's done, the pictures are distant.

    What he's PROBABLY doing, is powering across two legs, and putting a capacitor on the third, which phase shifts it the same way my coversion works. This is what I suggested to others faced with the CP200 welders that were set up for 208/230v only.

    The result is basically the same, but that one leg is not subjected to current flow in as predictable a manner, because it's actually a midpoint across two coils.

    Because of the complexity of what's happening, I recommend you start with a SMALL capacitor, and put an ammeter on the wire between that cap and the leg it feeds, and then test weld, and observe leg current... then add a little at a time until you either reach an acceptable welding output, OR the current on that leg starts approaching about 60% of the other two... I wouldn't push it further, as your variables change significantly under load, you'll start seeing some really difficult electrical loading going on. Realize, the capacitor LIMITS the MAX amount of AC current that will flow.

    Also note- in my calculations, I made one incorrect assumption: Frequency.

    When I first brought the concept up with Peter, I was sitting in a booth at a favorite neighborhood haunt with an order of beef-and-bean burritos and a Pepsi... I'd drawn it out on a napkin... and I based my capacitor calculations on a frequency of 60hz, which is line frequency, right?

    When I set up my first unit (which is still well operational, btw), I noticed that my current and voltage numbers were not quite where I expected. I was working on a different model a year later, when I recognized my error- the alternation which occurs, is not occuring at THREE 120 degree intervals in a full cycle... it was occuring at FOUR times (quadrature) in a full cycle. That means that my operating frequency was actually 360/3*4= 80hz.

    SO...when you're doing THIS type of mod, re-run your impedance calcs and capacitor estimations based on 80hz, not 60.

    Between that, and starting small on the caps, you should be fine. If it were me, I'd skip the math and start with 30uF, take a current measurement while welding, and then add another 15uF, test again... then swap the works for a 50uf, test, then another 15... then exchange that for the 30... etc. I would not expect (from my personal experience) to be over 150uF. I would NOT jump in with 600uF.


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