Help with a Rotary Phase Converter and an Inverter Welder
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  1. #1
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    Default Help with a Rotary Phase Converter and an Inverter Welder

    Hi all, I was wondering if I could draw on your collective experiences to troubleshoot my electrical issue, please. I was wondering if anybody out there has ever had an issue with running a 3PH inverter welder MMA/tig with a rotary phase converter(RPC)? I have 240v single PH input converting to a transformed 415V output run by a 13.5 HP/19.7 Amp idler motor with various capacitors in place. The RPC was purchased about 14 years ago and runs various 3PH machines. The welder is a Kemmpi MLS2500 inverter welder. When connected, the welder turns on but it doesn't want to ARC?, The Kemmpi's specs are 3PH, 400v +20%/-15%, 10A with a kVA between 7.7 - 9 kVA.

    So far I'm at a loss as to why it's not working?

    Regarding troubleshooting so far I have:
    1/. Checked the voltage and Swapped all the phases and tested it, but no chocolates.
    2/. Taken the welder to a mates Factory to confirm the welder is working on grid 3 phase 415v (which it works fine)
    3/. I measured the volts between phases:
    L1 - L3 = 416V
    L2 - L3 = 434V
    L1 - L2 = 458V
    Averages 436volt (should still be in spec?)


    I am thinking of a few possibilities:

    a/. Maybe the voltage tolerances between phases are too far apart for an inverter type welder? (does anyone have experience with this?)

    b/. Maybe the welder is having trouble processing the input power signal from the RPC? (maybe an inrush current issue?. However, there is no Amp draw on the idler motor when I load tested it with a clamp meter when trying to create a weld arc!).

    c/. as per (b) Not enough Amps to start the arc process?? (mind you the welder's specs say 10A and I know the RPC can output 19A when I load tested it on the panel saw?.

    d/. Maybe it's a voltage balance issue? (a)(once again any pointers on DIY here would be really appreciated!)


    Anyway, If anyone has had similar experiences, or members out there have an idea, I'd love to know your thoughts or how you would overcome it or overcame it.

    Thanks for reading

    Chris

    img_7910-copy.jpg
    Attached Thumbnails Attached Thumbnails drawn-schematic.jpg   rough-hand-schematic_1.jpg   rough-schematic.jpg  

  2. #2
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    I am just guessing as to what the issue is. RPCs are successfully used to run VFDs so it should be possible. Try the things below to see if they have any effect. If they do, it should provide some clues.

    Things you could try: Swap the phases to the welder. Imbalance or missing phase detection might be an issue. Remove some balance capacitors to try and get the highest voltage leg (assuming l1, l2 is generated) down. Turn on that another 3 phase motor load, the bigger the better.

    Bill

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    Thanks for your suggestions Bill, really appreciated


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