Adding a smoothing capacitor to a Clarke mig

  1. choco

    choco Member

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    373
    ireland
    Would anyone know what spec capacitor/s would be needed for a Clarke 160en and what value bleed down resistor?
     
  2. R Kraft Member

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    863
    Wyoming,USA
    Usually between 60,000 and 100,000uf at 60-70v and a 50 to 75ohm resistor at 20w.
    I will need to look at the wiring diagram, to know if the wirefeed will be okay with the added capacitor.
     
  3. choco

    choco Member

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    373
    ireland
    Great thanks , I'm going to run a separate PSU for the wire feed.
     
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  4. Seadog

    Seadog Forum Supporter

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    You may find that you'll need to add an inductor in series with one of the leads to limit current surge.
     
  5. choco

    choco Member

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    373
    ireland
    Thanks seadog, space could be a problen then. I thought I'd be able to get away with just adding a big capacitor
     
  6. Seadog

    Seadog Forum Supporter

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    The problem is there's nothing to limit the surge cuurent, so you've the potential to blow holes in thinner gauge metal.
     
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  7. eddie49 Member

    Any MIG welder worthy of the name should already have an inductor ( choke ), normally in series with the welding return lead ( "earth" lead ).
    The added capacitor(s) should be fitted just after the rectifier, across the output, before the inductor.
    Three or four of these capacitors wired in parallel with busbars should be enough:
    https://www.ebay.co.uk/itm/Kendeil-...-Aluminium-Electroltic-Capacitor/222562911534
    Some welders use the clever idea of an extra pair of normally-closed contacts on the contactor to only put the bleed resistor across the capacitors when the contactor drops out, and take the bleed resistor out of the circuit when the welding power is on. That way you can have a lower resistance value, such as 20 to 30 Ohms ( = quicker discharge ), and it doesn't waste power during welding.
     
    Last edited: May 17, 2019
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  8. mike 109444

    mike 109444 Member

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    4,043
    uk Bristol
    The 160 already does have an inductor (as most of the Clarkes do).
    As it's an EN you will need to take care where you insert the cap (as it will be polarity conscious ) and the machine has the ability to swap polarity ! (diagram does not indicate where Clarke does this.
     
    • 160 EN INDUCTOR.jpg
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  9. Seadog

    Seadog Forum Supporter

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    It would seem that they're in the side cover and swap the leads after the inductor, so there wouldn't be any polarity issues with the capacitor.
     
  10. Wildefalcon Member

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    What does this add to a welder? I've a Clarke 160 something, what would this give me that the machine doesn't do now?
     
  11. Seadog

    Seadog Forum Supporter

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    If you use gasless wire you need to change the polarity.
     
  12. mike 109444

    mike 109444 Member

    Messages:
    4,043
    uk Bristol
    It "should" smooth the DC output of the weld.
    I have a very old clarke machine that came as standard with a capacitor. The connections on the capacitor became intermittent "poor connection" and as a result the weld penetration was next to non existent on 1.2 mm sheet! Tracked down fault and sorted to restore correct penetration. Understand that this machine was built (designed) with an inductor AND capacitor as part of it's makeup.
    pics below.
    1st inductor on left side vertically mounted.
    2nd single big cap
    3rd and 4th experiments with original cap, new cap (bigger value) and both caps together. As you might be able to see there was not a lot between the combinations so I stuck with a single cap and used the spare to add to another machine.
     
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    • front.jpg
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  13. mike 109444

    mike 109444 Member

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    4,043
    uk Bristol
    ps machine has 6 power setting !
     
  14. choco

    choco Member

    Messages:
    373
    ireland
    I'll take the cover off the machine on Sunday and see is there an inductor. Would one big cap work?? 47000uf 50v ??
     
  15. eddie49 Member

    You could try just one large one, but most machines that are originally designed to include caps use a bank of medium-value ones:
    capacitors.jpg

    There is a thread on here discussing the advantages ( if any ... ) of sharing current across multiple capacitors.

    Are you planning to weld thin steel, or thick ( >3mm ) stuff? If thin, is your current lowest setting OK for you, or a bit too high?
    Bear in mind that capacitors will store energy and smooth the ripple that you normally get with simple rectified AC, thus increasing the average power at each setting. A large value - 50,000 uF - compared to a smaller one - 20,000 uF - may make the lowest setting too high for thin metal.
     
  16. Seadog

    Seadog Forum Supporter

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    In which case a larger value of inductor might be of benefit.
     
  17. choco

    choco Member

    Messages:
    373
    ireland
    I tend to use the mig more for thinner stuff,(and it's great as is for .8mm car panels. i use the ARC for over 3mm. So a bank of lower uF caps would be better than one single bigger uF value?
     
  18. Seadog

    Seadog Forum Supporter

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    Only if they're switchable. If they're all connected together they are effectively one large capacitor. It doesn't matter if you have one large or a thousand small ones, the effect is the same.
     
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  19. eddie49 Member

    Without trying it, it would be hard to predict exactly what the effect of adding 5,000 or 10,000 or 50,000uF of capacitors will be, and whether it will be helpful in your usage of the welder.
    With capacitors in parallel, the total effective value is the sum of the individual sizes. If you buy one or a few smaller caps, e.g. 5,000uF, you can start low and keep adding, but if you can get that 47,000uF/50v for a decent price, then give it a try. That 50v DC rating is on the limit - my Sureweld Monomig 140 has an open-circuit voltage of 43v on the highest setting. You can check your DC volts from the torch tip to the earth clamp at the highest power setting.

    For this type of application, the best capacitors are those called "Computer Grade", or "Low ESR" ( equivalent series resistance ), or "High Ripple Current", and with large screw terminals, rather than solder or push-on tags.

    This is the thread that discusses the possible advantages of having multiple smaller capacitors:
    https://www.mig-welding.co.uk/forum/threads/180-capacitor-swapout.63068/
     
  20. Rig Pig

    Rig Pig Member

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    And the old girl is still chewing 0.8 ;)
     
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