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89893Re: [mach1mach2cnc] Power supply caps

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  • Brian Foley
    Apr 3 12:35 AM
      Hi, well there are formuleas and then there is good enough, and then cheap
      enough....the best i can say is more capacitance wont hurt.....something
      around 33,000 uf to 40,000 uf should be fine, however i want to see 60 volt
      caps so unloaded the cap wont be overvolted...even a bit higher is a little
      more safety margin........however more expense....
      if i was building i would get 65 or 70 volts, and look for something
      33,000uf or a few thousand more up to 40,000 uf..
      once you get beyond 40,000 then you need to think about soft start.......to
      limit the inrush current(turn on current).....
      i am available most anytime to chat off line, i suspect its a power supply
      for a cnc machine. cul brian f.


      www.genapro.com
      ----- Original Message -----
      From: "Andrey Lipavsky" <alipavsky@...>
      To: <mach1mach2cnc@yahoogroups.com>
      Sent: Wednesday, April 02, 2008 10:59 PM
      Subject: [mach1mach2cnc] Power supply caps


      > I'm building a power supply and have a question on cap size.
      >
      > My toroidal transformer will supply 40V at 24A. Now, according to the
      > standard cap formula, I would need roughly 30K-uf to sustain the 55VDC at
      > 20A (derated to 80%).
      >
      > My question is why none of the over-the-counter power supplies in this VA
      > bracket seem to use so much capacitance? Is this really overkill or are
      > they just cutting corners?
      >
      > Thanks,
      > Andrey Lipavsky
      > Essex Jewelers
      > 490 E. McMillan St.
      > Studio 205
      > Cincinnati, OH 45206
      > (513) 826-0240
      > www.essexjewelers.com
      >
      >
      >
      >
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