0-100 amp continuous current adjustment

Discussion in 'The Projects Forum' started by edsaldana, Feb 17, 2012.

  1. edsaldana

    Thread Starter New Member

    Feb 17, 2012
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    0
    I need to adjust DC current to a resistive load (heater) from 0 -100 amps.
    The adjustment needs to be done with a potentiometer and not by PWM.
    The source is 48 volts DC.

    I was thinking in usng a IGBT, but can't find any reference or sample circuit for this aplication.
    Does anybody have any idea how to start?

    Thanks!
     
  2. jimkeith

    Active Member

    Oct 26, 2011
    539
    99
    What you need is a buck regulator.
    The input to the inductor will be pwm--the output will be DC.
    Obtaining a suitable inductor will be more of a problem than the IGBT.
    A swinging or saturable reactor may be required to keep the current from becoming discontinuous at low settings.
     
  3. bountyhunter

    Well-Known Member

    Sep 7, 2009
    2,498
    507
    How about a pot that controls the pulse width? A switcher changing the PW is really the only feasible way to do this.
     
  4. crutschow

    Expert

    Mar 14, 2008
    13,000
    3,229
    You do not want to use any linear type of control since the power dissipation of the regular could be upwards of 2500W.

    PWM (a switching regulator) is the best way to do it. If you just want the current to be adjustable and it doesn't have to be extremely stable with time and temperature, then a simple PWM controller and driver (with a inductor filter if necessary) should suffice.
     
  5. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    Hello edsaldana and welcome to All About Circuits.
    100 amps at 48 volts DC?

    A small old fashioned welder might operate at these levels. Try a machine supplier for the controller from one. It should do your job.
    But be sure to house it in a well ventilated cabinet for cooling.
     
    Last edited: Feb 18, 2012
  6. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    What's the heaters resistance?

    Why can it not be PWM?
     
  7. edsaldana

    Thread Starter New Member

    Feb 17, 2012
    3
    0
    The resistance is only .5 ohms.
    What about using a high current Darlington in series with the load and controlling the current by adjusting the base voltage?
    Would be too inefficient?

    Thanks a lot for all your comments!
     
  8. kubeek

    AAC Fanatic!

    Sep 20, 2005
    4,670
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    Let´s see, say you set 50A to flow through the load. That way, the voltage on the load is 25V, and the voltage drop on the pass transistor is 23V. The power dissipated by the pass transistor is 50A*23V=1150W. I have no idea how you plan to get rid of such heat, even if you had a large bank of transistors that would survive such power.
     
  9. bertus

    Administrator

    Apr 5, 2008
    15,647
    2,346
    Hello,

    Our company makes powersupplies for electromagnets.
    There is a 2.7 kW version, that uses water cooling for the powersupply.
    It has a transistorbank with about 40 transistors that are mounted on a thick plate with pipes going between the transistors for the water cooling.

    Bertus
     
  10. studiot

    AAC Fanatic!

    Nov 9, 2007
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    Please note the dates on the original posts.
     
  11. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    I hope the next reply won´t take the OP another 14 months.
     
  12. edsaldana

    Thread Starter New Member

    Feb 17, 2012
    3
    0
    Thanks Kubeek, so I guess the best option is to use a PWM. Do you think the VLA507 will work? I´m planning to order few of those to play around and see how it works. I will use some 200 amp IGBTs I have with me.


     
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