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Repairing huge welder, Blown Caps

Discussion in 'Troubleshooting and Repair' started by Paul of Chester, Oct 3, 2012.

  1. Paul of Chester

    Paul of Chester

    3
    0
    Oct 3, 2012
    Hello everyone,
    I have read many of your posts over the last year but this is my first post.

    I am repairing a large MIG welder. As I fix one problem it usually makes the next problem come to light. I think I am fixing the last issue. It has six large capacitor (slightly smaller than soda cans) in parallel, 10,000uf at 75VDC. One is spraying out the top like an aerosol can. I have an endless supply of free large capacitors of other sizes. Naturally I would like to use these. I went to look for the closest match and came home with 24 capacitors of 2,400uf at 600VDC.

    If I am adding the capacitors "plate" surface area when in parallel, can I use 25 of the larger 2,400uf caps?

    Please see attached image/diagram.

    Paul
     

    Attached Files:

    Last edited: Oct 3, 2012
  2. MrEE

    MrEE

    84
    0
    Apr 13, 2012
    Total capacitance is the sum of all capacitances when connected in parallel. In your case, 25x2400 = 60000 uF is correct. (unit is uF or microfarad and not ohms). If you have the room why not add a few more.
     
  3. Paul of Chester

    Paul of Chester

    3
    0
    Oct 3, 2012
    Thank you MrEE,
    I was suspecting I could add two extra for a little safety but wasn't sure if that would screw up something else.
    You are right about ohms, it was late when I created that graphic (obviously too late), I will correct it for future readers. Will the higher voltage matter? I would think a little higher would not but almost 10x?

    Thanks for your help.

    Paul
     
  4. MrEE

    MrEE

    84
    0
    Apr 13, 2012
    In general higher rating caps is no problem. The ESR (equivalent series resistance) might be higher on higher voltage caps, but you have so many in parallel that I don't see an issue here. I'll give it a try.
     
  5. Paul of Chester

    Paul of Chester

    3
    0
    Oct 3, 2012
    Thanks MrEE,
    I'll get three more caps this Friday (the 1 I am short & 2 for elbow room) & work on it over the weekend. I'll keep you posted.

    Paul
     
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