H-bridge multilevel dc/dc converter with resistive load

Discussion in 'General Electronics Chat' started by khalid4145, Oct 8, 2008.

  1. khalid4145

    Thread Starter Member

    Jul 22, 2008
    16
    0
    Hi there,,,

    can any body help me in finding applications of using H-bridge multilevel dc/dc converter or H-bridge dc/dc converter with a resistive load? Any ideas?
     
  2. khalid4145

    Thread Starter Member

    Jul 22, 2008
    16
    0
    It seems no boday wana help :(
     
  3. mik3

    Senior Member

    Feb 4, 2008
    4,846
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    A pure resistive load is a resistor which is still not a pure resistance but it has a tiny amount of inductance and capacitance!

    What exactly you want to do?
     
  4. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Are you looking for a list of products with resistive loads which employ such a power supply? Do you wish to study the supply as it drives a resistive load? Can you re-phrase your question?
     
  5. khalid4145

    Thread Starter Member

    Jul 22, 2008
    16
    0
    Actually i am doing a experiment using H-bridge multilevel dc/dc converter supplied by four power supplies each of wich is 30V (total 120V). the converter is connected to a load which is a pure resistive load of 15 ohms carrying maximum of 8A. i just want to know is there any application to my experiment (ie. H-bridge dc/dc converter ( + and - voltage) connected to a pure resistive load). Please help.
     
  6. steveb

    Senior Member

    Jul 3, 2008
    2,433
    469
    I'm not sure if these are good examples. As was already pointed out, pure resistive loads are hard to find. Two things come to mind though. A resistive heating element to heat the air, or a water pot. And, a thermoelectric cooler (TEC) (also called a Peltier Cooler) which can heat and cool based on the direction of current flow.

    I guess these applications would allow you to precisely control the heating (or cooling) by varying the average current via PWM. This is more accurate than using a simple thermostat with on/off control.

    You can use a proportional-integral control loop rather than a bang-bang control. The TEC application seems to be appropriate for an H-bridge since you can heat or cool by changing the current direction.

    One issue with TEC coolers is that the PWM frequency impacts reliability. I seem to remember something about the frequency needing to be above some number in the 1-10 kHz range, but check to be sure.

    As far as the TEC being a resistive load, I think that that is a good approximation if the wires are short. The typical resistance is of the order of 0.1 to 10 Ohms. However, the resistance is very nonlinear, meaning the resistance depends on current.
     
    Last edited: Oct 21, 2008
  7. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
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    I don't get it... why does the load have to be resistive? What happens when this converter is hooked up across a radio or a pump motor or something?
     
  8. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Most commonly, H-bridges are used in the control of DC motors or bipolar stepper motors. They're reactive loads due to the inductance of the windings. They could also be used to drive the primary side of a transformer in an inverter scheme, but that's also a reactive load.

    A Peltier device is the only resistive device that comes to mind that would be practical for use with an H-bridge.
     
  9. khalid4145

    Thread Starter Member

    Jul 22, 2008
    16
    0
    Thanks for all of you guys for useful informations. A special thank for Steveb for detailed information which really do help me.
     
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