12V-1000Amp Load

Discussion in 'The Projects Forum' started by tikki, Dec 27, 2010.

  1. tikki

    Thread Starter New Member

    Dec 22, 2010
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    Hey Guyz..

    I wanted to make an load which will stand at 1000amp 12V.

    I made an load which can stand till 200-300Amps only. The load is with Metal plates on parallel.. and with the help of salty water.

    But now I want to test some of my new instruments like IGBT rectifier and SCR rectifier as an I am Testing engineer. Because these rectifiers have rating of 1000Amp to 2500Amp. So does anyone knows anything regarding with that. Can anyone tell me how should I make a load which will stand at 2000Amp or 1000Amp?
     
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    How accurate does the load need to be?

    There are electronic loads that are very well regulated, but are correspondingly priced.

    Some form of water cooled current sink, such as resistance, seems to be the solution for that amount of power.
     
  3. retched

    AAC Fanatic!

    Dec 5, 2009
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    A salt water current sink would be the least expensive way to go about it.

    Accuracy increases price. Keeping the tank at set temperature and pressure increase accuracy and price.

    I have not seen any available for sale on the consumer market, I have only seen them custom made.
     
  4. marshallf3

    Well-Known Member

    Jul 26, 2010
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    You can get battery testers that will go that high on a very intermittent (low duty cycle) basis, they use a large resistive heating element inside them.

    They also make 12V water heaters for RVs but it would take a lot of the elements to add up to a 1000A load.

    That's 12KW you're trying to deal with.

    Alternately, what if you used a few of the inexpensive 12V:120V inverters that are so cheap on the market nowadays then just load the 120V sides down?

    Of course if it's a necessity to have precision: http://www.manatronics.com/
     
  5. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    We have a 2000 Watt 28 volt load at the shop. It's about the size of two tower computer cases stacked sideways. 3 ft by 1ft by 2 ft tall. 16 Gauge stainless steel case with ceramic standoffs. Hold the element. A convoluted copper plate arrangement. The plates are .100 inch thick and the unit has 14 milliohms of resistance. It has a duty cycle of 30 seconds in 2 minutes with the fans running. The motor used to start the jet engines is run on 28 VDC and we use the load to test supplies before we ship them.

    [​IMG]
     
  6. JDT

    Well-Known Member

    Feb 12, 2009
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    So you want 12mΩ (0.012Ω) and dissipate 12kW. I like the steel plate or steel strip idea. Even better would be stainless steel because it has a higher resistivity value. If you measure the cross-section area of your strip and find out the resistivity value of the material (look on-line or in an engineering reference book), you can work out the length required.

    For cooling, I would submerge the whole assembly in a tank of water. The small amount of current that would leak through the water at 12V will be negligible compared to the 1000A flowing through he strip.

    Best not to coil up the strip because the magnetic field will cause the turns to want to touch. Better to zig-zag then the magnetic field will tend to cancel out. Will still need to be rigidly supported though.
     
    tikki likes this.
  7. retched

    AAC Fanatic!

    Dec 5, 2009
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    I remember reading about someone who visited a steel/iron smelting plant and saw some HUGE wire runs.

    Apparently the current was SO GREAT in these runs that your ankles vibrated..from the IRON in your blood becoming magnetized.

    Now that is some serious current.

    I like the steel plate idea as well.

    I dunno if water would be the best insulator, I would look into mineral oil.
     
  8. Kermit2

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    Feb 5, 2010
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    There is a good reason copper is used. You need lots of surface area exposed to radiate the heat. With steel or stainless, the resistance is too high. You would never get enough surface area for cooling, without increasing resistance too far to pass the needed current.

    Remember we only use a fan (a normal size box fan) for cooling.
     
  9. retched

    AAC Fanatic!

    Dec 5, 2009
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    Good call.

    With the price of copper these days, that would be quite an investment.

    BUT, it takes money to make money.

    If you need it to produce a part or product, then so be it.
     
  10. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Why can't the supply be connected to a DC motor rigged as a dynamometer? Or, maybe as a big fan to cut down on A/C bills? ;)

    John
     
  11. Kermit2

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    Feb 5, 2010
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    We make an APU that is driven by helicopter engines under test.

    The old water dyno's we replaced with DC generators and a 14.4 KV power conditioner for backfeeding the grid.

    Now when they test the engines, the hush house makes enough 'juice' to power a portion of the base.

    www.atec.com
     
  12. tikki

    Thread Starter New Member

    Dec 22, 2010
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    Thanx a lot guyz..

    Thanx for all your help. But as I said.. that right now i m using that water cooling technique with the help of salt water. But its only going upto 300 Amps.. I know in some electroplating companies where we sell our IGBT and SCR rectifiers...they use a load which stands upto 3000Amp.. But their load consumes a large area plus a good chemical as they have a electroplating plant.

    But now as I am an Testing engineer we cant afford that much big plant.

    One more thing is there and that is.. when we went to china to buy these rectifiers.. they were using the same load.. in which some of the plates were joined in proportion... and kept in water.. but when we asked them that which metal it is they replied that it is special kind of material...thats wat they replied..


    So.. right now our main aim is.. that to make a heater load which will stand at 1000amp and 12 V...

    So does anyone knows that which metal stands at that much high current?
     
  13. Wendy

    Moderator

    Mar 24, 2008
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    Instead of one load, think many. A 10A resistor is easy, even if it is homemade. Use X100 of them and there is 1000A.

    Reminds me of a story my brother told me about a new massive power supply his company had gotten. His manager (who was not technical) wanted to to test it at full load just to be sure it worked. I don't remember what the specs were, but they were fairly large. Just for the sake of argument lets say they were 24V at 500A. After being rebuffed when my brother tried to explain what she was asking for he made an enormous space heater that still didn't come close to testing this unit. After seeing the bright glow and more importantly, feeling the intense heat on her face, she relented. Several engineers were in back of the room laughing at the time.

    The moral of this story is you need somewhere to dump the waste heat. Mineral oil is good (unless it catches on fire), and water doesn't burn, but you need a continuously moving bath of something.

    It also goes without saying you need some fairly massive bus wires. To me that would seem the greater challenge. 10W resistors are cheap, metal is expensive.
     
  14. Kermit2

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    Feb 5, 2010
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  15. marshallf3

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    Jul 26, 2010
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    That's a bargain considering what I found. Note that the shipping charge eBay originally shows doesn't coincide with his text afterwards so if you're going to order some be sure to keep in contact with the seller so he can send you a proper invoice.

    Both Singapore and California are mentioned so that may be the problem. Just don't get hit by a mistake.
     
    Last edited: Dec 29, 2010
  16. tikki

    Thread Starter New Member

    Dec 22, 2010
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    Thanx a lot Bill, Kermit and marshalf

    @ Billl.... Hey dude.. will that work? Actually you are saying to connect the several resistors in parallel... which will carry the mulplication of current. But if we see practically according with the KCL... so there may be the problem...

    can you tell me that how much space will it take and what are the other things which are required for this? Should I go for this Resistive load?
    Will it stand at 1000Amp? Or it will melt?
     
  17. Wendy

    Moderator

    Mar 24, 2008
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    I've been browsing combinations. You need a resistance of 0.144Ω at 1000W, 83.33A.

    How about qty 7 1.0Ω 225W resistors in parallel (0.143Ω, 84A, 1008W). Each resistor costs $12.90 each, qty discount for 10 at $117.25.

    http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=HLD-1.0-ND

    Another approach, find the cheapest resistor you can get, such as this one...

    http://www.bgmicro.com/RES1365.aspx

    10Ω 25W at 49¢ each, and make a network out of them. 70 of these in parallel would be .143Ω, dissipate 1008W (seems to be a magic number), with a max power of 1750W (comfortable safety margin there), and would cost $34.30. This price would likely be negotiable from the vendor.

    There is a third approach, one I'm currently looking for a case to build as a project. Build a simple transistor constant current source. Each transistor can dissipate 100W with a good heat sink, build 10 of them and you have an electronic load.

    Electronic Loads
     
  18. Rbeckett

    Member

    Sep 3, 2010
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    Another thought is to look in the automotive service world for a carbon pile load tester, but they do have a limited duty cycle. We used them very often to load test large diesel engine starting systems as well as apply loads to large generator sets to verify perfomance within spec. Catapiller and cummins supply these generator sets and have the device you are describing, but they are sort of expensive. Sounds like you are in manufacturing and need a verifiable standard so you should probably make sure that what ever you decide to use is calibrated and kept in calibration to obtain any type of ISO certification later on. Any home made system will be hard to prove calibration on and result in a big hassle if you are tyring to obtain any type of manufacturing quality certifications in the future. Just some thoughts from an old cat generator guy. PM me if you need info on the test equipment we used and where to obtain it.
    Bob
     
  19. retched

    AAC Fanatic!

    Dec 5, 2009
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    He needs 1000A not 1000W.

    Thing is, what voltage will you be testing at?

    If it is 20v and 1000A, that is 20,000w or 20kW
     
  20. marshallf3

    Well-Known Member

    Jul 26, 2010
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    Last edited: Dec 29, 2010
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