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High current connectors

Discussion in 'Electronic Design' started by [email protected], Aug 21, 2005.

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  1. Guest

    Can anyone comment on what's the 'right' way to connect high current
    sources to a PCB? Can anyone recommend a particular connector? Assuming
    I don't want to do something like solder the cable directly to the
    board.

    I'm looking at 40A, but for the sake of learning something, I'd be
    curious to know what people use for 60A, 80A, 100A or above, and for
    that matter, what the limit is.

    Thanks,

    Chris
     
  2. Yukio YANO

    Yukio YANO Guest

    Look up the Fork-lift servicing people in the phone book . They have
    standard Connectors for wheel-chairs to Industrial Fork-lifts !

    Yukio YANO
     
  3. Guest

    Yeah, but are the PCB mount?

    The forklift we had in our back shop had a nice high current connector,
    but it was cable to cable, rather than cable to PCB.

    Chris
     
  4. John Larkin

    John Larkin Guest


    I sometimes use a regular nylon-shell Amp or Molex connector at, say,
    5-10 amps per pin. Inter-board cables are run with one modestly-sized
    wire per pin pair; that's cheap, easy to fab, flexible, and the wire
    resistance equalizes pin currents if you plan it right.

    Somewhere north of 50 amps RMS, current crowding and power dissipation
    in the PCB traces becomes a problem. A big connector with lots of
    smallish pins helps here, by spreading out the current footprint.

    John
     
  5. Terry Given

    Terry Given Guest

    AMP now make them, but we designed our own. Make a big fat (red) cross,
    out of 1mm Cu, with fingers on each of the protrusions, and a hole in
    the middle. Fold the protrusions down, to make a little box, and drop
    into a suitable PCB footprint (fingers thru holes get soldered). Then
    unsolder it, and pop a suitable sized nut underneath (appropriate hole
    on PCB) then re-solder, and voila - a nice high-current connector you
    can bolt too. After you forget the nut once, you wont forget again :)

    careful choice of dimensions mean the nut is contained but cannot spin
    freely. poor choice of dimensions renders the idea useless.

    Others just bolt big fat lugs directly to PCBs, but beware the Z-axis
    CTE of FR4 is about 10x worse than X- and Y-axis CTE, and that near Tg
    it'll happily flow. Still, thats what Mithras invented Schnorr washers
    for :)

    Cheers
    Terry
     
  6. John Larkin

    John Larkin Guest

    Why solder/unsolder/resolder?
    Yup, did that whan I was young and foolish. Lots of trouble.

    The problem isn't so much the connector as it is the current
    distribution and heating in the PCB traces. It's fairly easy to get
    most of the current squeezed into a relatively small part of where you
    expected it to be. The Amp block-o-pins thing has such a low
    resistance that the pcb pad/trace geometry is going to determine the
    current sharing. I like the multi-wire thing because it can be made to
    force a nearly equal current on each pcb pad, and can spread out that
    current over a wide area. Plus, the octipus of wires just above the
    shell housing provides much better air cooling than you'd get from a
    single equivalent fat wire.


    John
     
  7. Terry Given

    Terry Given Guest

    just a cheeky comment. And because most people do that, at least once.
    oh yes. a terrible idea.
    and a split-washer (cheap shit spring washer) exacerbates the problem,
    by heavily loading one point.

    Cheers
    Terry
     
  8. Guest

    I have used wire-mounted "Singlepole" and "Multipole" Anderson connectors
    http://www.andersonpower.com/ for DC (150 V, 150 A) and AC (300 V, 70 A)
    connections and they seem to work well. It looks like they do a PC-mount
    version of some of their connectors (which I haven't used) for up to 55 A.
    Big copper land on PCB, big bolt, ring terminal...

    Thinking out loud: do you know about the lugs that are used to terminate
    larger stranded wires to fuse holders, etc? Like
    http://www.gardnerbender.com/whats_new/products/ima_prod/alu_lugs.jpg .
    Maybe you could use a lug like this, bolt the thin part to your board
    permanently, and have the user insert a stranded wire into the hole and
    tighten the screw. Essentially it's a DIY high-current terminal strip.

    Standard disclaimers apply; I don't get money from any of the companies
    mentioned.

    Matt Roberds
     
  9. Rich Grise

    Rich Grise Guest

    And less impact from skin effect. ;-)

    Cheers!
    Rich
     
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