20V 1000A power supply for direct resistance heating of stainless steel tube

Discussion in 'General Electronics Chat' started by timgow, Nov 23, 2015.

  1. timgow

    Thread Starter New Member

    Aug 12, 2015
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    Hi,
    I need to heat a bundle of stainless steel tubes in an experimental R&D heat exchanger. I'm following a published technique that uses a pair of Sorensen 20V 1000A power supplies in parallel; the total resistance of the tube assembly is 0.0019 Ohm. The published results show the Sorensen units running at 3.8V.
    The publication is early 1980's so I have a couple of questions:
    Is there a commonly available make and model of DC power supply in this operating range?
    Are there any known books or articles that cover the construction of high power, low voltage DC power supplies?
    I appreciate your help.
    Tim
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    Did you check Sorensens website or call them for help?
    They are still around and still make power supplies.. and still have what you need

    Hope you have a big checkbook...
     
  3. timgow

    Thread Starter New Member

    Aug 12, 2015
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    Hi McGyvr,
    I would like to search out some used units as the new Sorensen units are indeed big money.
    Are there other manufacturers in that market? I need other names to search on with dealers and ebay.
    Is there a basic design configuration for this type of low voltage/high current power supply or is there some proprietary Sorensen technology that prohibits constructing a unit from scratch?
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Why do you need DC?
    A simple resistance welding set up should work, and either timed contactor on the primary or POWER triac.
    Max.
     
  5. alfacliff

    Well-Known Member

    Dec 13, 2013
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    check with plating companies and suppliers. we use supplies here up to 15,000 amps in plating and anodising.
     
  6. timgow

    Thread Starter New Member

    Aug 12, 2015
    10
    0
    Hi MaxHR,
    I'm focusing on DC so that I don't have the complication of inductance and skin effects within the tube bundle; I need to be confident of my resistance heating performance prediction before purchasing the power source. I started out weighing-up whether arc welding plant would perform the task but the low resistance of the proposed load doesn't suit the ~50V open circuit SMAW welding voltage.
    I hadn't thought of resistance welding sets, they are likely to be low voltage / high current, although AC.
    I can reconsider the use of an AC source, if the source is readily available and lower cost than Sorensen type lab equipment.
    Thank you so much
     
  7. PeterCoxSmith

    Member

    Feb 23, 2015
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    38
    I bought a second hand power supply rated at 350A, 10V from this company in the UK:

    http://www.telonic.co.uk/
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,555
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    The skin effect on 50/60hz should not be a problem.
    SMAW is not a good choice as you would not get the required current.
    Resistance welders typically go up into the 10,000's of amps secondary.
    The down side is the very low voltage may be a hindrance if the resistance is significant.
    Even my weller solder gun puts out 100amps!
    Max.
     
  9. timgow

    Thread Starter New Member

    Aug 12, 2015
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    Hi Alfacliff,
    I will check out electrolysis plating equipment, this is obviously DC. What are the characteristics of the plating and anodising power sources? Constant voltage? What range of control is typical, is 2000A at 4.0Vdc feasible?
    Many thanks for the lead
     
  10. timgow

    Thread Starter New Member

    Aug 12, 2015
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    0
    Peter,
    Thank you for the link, I see the 'Lab-Power LAB-DCH 20-1000 High Power DC Power Supply' in their listing.
    Much appreciated
     
  11. alfacliff

    Well-Known Member

    Dec 13, 2013
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    four of our anodising supplies rate 0-15 vold dc, 0 to 30,000 amps. fed with three phase 480volt ac. smaller ones are in the plateing shop. most of those type supplies do their regulating on the primary side.
     
  12. timgow

    Thread Starter New Member

    Aug 12, 2015
    10
    0
    I will check out the plating shop equipment market, maybe there's something second-hand out there.
    Is the voltage adjusted at the transformer? Is the current controlled or is it a consequence of setting the secondary voltage and the load resistance? I'm trying to visualise how I would control the power, starting low and increasing based on thermocouple temperature feedback.
    Thank you
     
  13. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    I would recommend renting the required power supply if this is a 1 time/low frequency need..

    But yes.. an anodizing power supply is a great/low cost choice
     
  14. Reloadron

    Active Member

    Jan 15, 2015
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    232
    During the early to mid 90s I did quite a bit of work with the MK50 torpedo program. To simulate the staem turbine generator we used a steam genny then ran the steam through turns of 1/2" 316 stainless pipe. There must have been a mile of the stuff in a big insulated box wrapped in refracil insulation. We used a pair of 1,000 Amp welders in a parallel configuration across the stainless steel coils. When this thing was fired up the stainless steel piping glowed cherry red. The end result was super heated steam and if I recall correctly ran about 2,500 to 3,000 PSI. Worked just fine for what we needed. Those welders would run into a dead short.

    Ron
     
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