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hefty amps-- DC 24-48V @ 1kA supply

Discussion in 'Electronic Design' started by Spehro Pefhany, Mar 11, 2008.

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  1. I need a DC supply (could be split into 5 supplies of 1/5 the current)
    that will handle a continuous current of 1000A total. So, 25-50kW,
    roughly. Ripple at 60Hz should be < 2%, regulation and any HF hash
    isn't too important.

    Any ideas for something (relatively) available/affordable?

    3-phase 480V/600VAC SMPS?
    MG set?
    diesel?

    Best regards,
    Spehro Pefhany
     
  2. Bob

    Bob Guest

    Since regulation isn't important how about a big stack of paralleled
    lead acid batteries? Star topology wiring would probably be best.

    Various manufacturers like lambda power and unipower-corp
    make SMPSU modules that work in parallel.
    Unipower TWRI series will do 9000 watts

    Bob
     
  3. Even expensive marine batteries will not supply that kind of current
    for long.
    That's interesting, thanks. Big bus bars I guess. Perhaps
    $0.50-$1/watt?
    Best regards,
    Spehro Pefhany
     
  4. Bob

    Bob Guest

    You can parallel enough batterys so that it is with the capability
    of the individual batterys, it's a question of run time between
    recharges
    and duty cycle because the batterys will take a while to charge.
    Can't comment on that without knowing the application.

    Elecsol lead acid batterys with carbon fibre in the plates are
    reasonably priced and can do high currents, deep discharge
    and 1000 cycles. The limited number of cycles could be
    a problem. The safety requirements for liquid acid batterys
    may also be onerous.

    Anyway I assume lead-acid is not going to work for you.
    Those manufacturers are at the high quality/high price end
    of things. They are a bit more than $1/w here but we pay
    far too much tax.
    If you want cheap you need to be looking at buying direct
    from China. For example these
    http://www.meanwell.com/search/SCP-2K4/default.htm

    Cheap and cheerfull is a bit worrying that this power level.
    I'd want to fuse the individual outputs and check the individual
    outputs with a clamp meter and trim them so they
    balance the load.

    Bob
     
  5. Boris Mohar

    Boris Mohar Guest

    A welding unit as a starting base?
     
  6. Most of the ones I've seen are not quite right, and the duty cycle is
    nothing like 100%, so it's not a great fit. Some welder mfrs make
    hefty DC supplies using similar technology, but they're still not
    quite there.
    Best regards,
    Spehro Pefhany
     
  7. John Larkin

    John Larkin Guest

    tdipower makes big stuff. I don't know how affordable it is.

    For non-surplus affordable, maybe a bunch of Meanwell switchers. Their
    stuff seems very good and is very low dollars per watt, as in $0.26
    per watt for an open-frame pfc switcher. I think they have some
    kilowatt-range stuff.

    I was/am considering stringing eight of their 48 volt switchers in
    series to get about 400 volts at 3 amps, for about $320 or so.


    John
     
  8. Tim Williams

    Tim Williams Guest

    Heh, I'm reminded of the tray of 100 x 100V, 20A darlington TO-3's I saw at
    work (2N6287??). Would make a great amplifier for some 0.05 ohm speakers.
    ;-)

    Tim

    --
    Deep Fryer: A very philosophical monk.
    Website @ http://webpages.charter.net/dawill/tmoranwms

    http://www.speff.com
     
  9. My exact thoughts were: "that's a whole lot of 2N3055's" :)

    [...]
     
  10. Mmmm... 2N3055.. shiny...

    (but they're far from being darlingtons...)
    Best regards,
    Spehro Pefhany
     
  11. Fred Bloggs

    Fred Bloggs Guest

    Have you checked with these people:
    http://www.trcelectronics.com/
    Meanwell is just one brand they represent. The supplies including
    parallel and redundancy operation are top dollar compared to the simpler
    products of the same wattage, something like 5x; the cost break with
    quantity is good though.
     
  12. Duty cycle?

    My first thought if you had the room would be some high capacity
    forklift batteries.

    From (I think) a home power website

    http://www.energyalternatives.ca/catalogue/Categories/160.htm

    Depending on your duty cycle, you migh then get away with just adding a
    low power supply to keep the batteries topped up. More than a few hours
    or so sustained draw and you are talking a lot of battery though (you'll
    probably need that much to keep the resistance drop down).

    Not cheap, but neither is a 50kW supply.

    Robert
     
  13. You could use three single phase welding or plating supplies, one on each
    phase, and the outputs tied together would have fairly low ripple. The
    magnetics would be rather large, but the concept is simple. I have worked
    on DC circuit breaker test sets rated at 1500 amps at 12 volts continuous
    (that was the small one), and a large one rated about 6000 amps at 20 volts
    continuous, with pulses to 30,000 amps. That one was in a box the size of a
    bathroom, and used 24 4000 amp SCRs with water cooling. The SCRs were
    originally phase-fired to adjust output, but when we replaced them, we used
    the gates just for on-off control, and a motor-driven Powerstat to adjust
    the input voltage.

    I have seen high current industrial spot welders on sale cheap on eBay and
    surplus houses, and they convert the line voltage to DC, then use a high
    frequency inverter to much smaller transformers at 1000-2000 Hz or so. The
    output still needs to be hefty, but for 1000 amps a 1/4" x 2" bus bar
    should be fine. You could easily wind your own transformers from toroid
    cores. A 60 Hz toroid kit rated 1.4 kVA is available from www.toroid.com
    for about $100, but you would need to remove the 120 VAC primary and rewind
    it for 480 VAC at 2 kHz.

    The basic toroid has 0.7 volts/turn at 60 Hz, so it would have about 23 V/t
    at 2 kHz. So the primary would be a total of 20 turns. The power rating at
    2 kHz would be 46 kVA. You might derate a bit at 2 kHz due to core losses,
    but three of these puppies will certainly give you 24 volts at 1000 amps,
    and you can put two loops of bus bar through the cores to get 48 VDC. You
    will need some hefty rectifiers, but nothing extraordinary.

    The devil is in the details, which are left to the designer. The
    interesting part will be making a 2 kHz 50 kW inverter for 720 VDC
    (rectified from 480 VAC), but a 20 HP V/F motor controller should be able
    to do the job with a bit of hacking.

    Paul
     
  14. Fred Bartoli

    Fred Bartoli Guest

    Spehro Pefhany a écrit :
    Not that I have the answer but is it one unit or production?
     
  15. Guest

    I did a quick calculation, should be able to do the output inverter/
    rectifier for around $6000, thats at the usuall inflated UK prices,
    probaly half that if you source the parts localy. You still need a DC
    supply, 3phase 12 pulse transformer rectifier around 600v DC. I can't
    do it for you though, too far away, too much aggro.
     
  16. legg

    legg Guest

    You might check out second-hand 60Hz plating rectifiers. There were a
    number going cheap not so long ago, as the domestic board fab
    businesses in your area went overseas.

    They are typically 8-20V as I recall, and may look pretty seedy due to
    application environment, but were rated for continuous operation and
    sell by scrap weight + transport.

    RL
     
  17. Rich Grise

    Rich Grise Guest

    5X 250 amp CV welders in parallel? ;-)

    Good Luck!
    Rich
     
  18. Rich Grise

    Rich Grise Guest

    Submarine batteries or locomotive batteries would. :)

    Cheers!
    Rich
     
  19. I say, divide and conquer. That's what the HV
    tension-line folks do, hundreds of small modules
    that can handle a portion of the MV and current,
    each taking a piece of the total voltage & power.

    So, first, sets of 450 PFC DC supplies using
    1.2kV components, then say 20 small sets of
    2.5kW step-down modules using the 450V as
    input, and generating 50V (is that right?) and
    50A output each. Bottom line, design & debug
    bulletproof 2.5kW PFC and 50A step-down
    current-mode modules. Parallel 20 of them
    for your 50kW 50V 1kA supply.
     
  20. legg

    legg Guest

    This is not ~ surplus and is not advertized as shippable outside US,
    but Atlantic sells it's stuff on the Canadian E-Bay site, so the
    shipping advisory could probably be extended, on inquiry, as it is not
    a strict company policy.

    http://tinyurl.com/yq9qur

    RL
     
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