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Power in = Power outbut what about for solenoids?

  1. May 18, 2005 #1
    Ok. so assume that you have a solenoid running about 12V DC and 1 amp. thats 12W. So that would suggest that this solenoid would have 12W of power when it performed tasks or needs to use that much power. But, different core materials make the solenoid more POWERful correct? (i may be misinterpreting this completely...) but how does it do this, and to what degree? (since power in = power out)
     
  2. jcsd
  3. May 18, 2005 #2
    It depends how efficient the solenoid is in converting the incoming power into something useful. A certain amount of the "power in" will be lost to electrically resistive loading for example, and dissipated as heat. Or the mechanics of the solenoid may use up the power by friction in the movement.

    Different core materials have different reluctances which may effect how much power is needed to drive each type of material. For example it will take more power to persuade an air-cored solenoid to move than an iron-cored solenoid.
     
  4. May 18, 2005 #3
    so then using iron as a core just technically makes it more power efficient?
     
  5. May 22, 2005 #4
    pretty much
     
  6. Jun 10, 2005 #5
    Power in = waisted power . . .
    A solenoid does "usefull work" only during the fraction of a second when the plunger moves. Once the plunger stops moving - all the power you are supplying is turned into heat - waisted.

    Oleh
     
  7. Jun 10, 2005 #6

    FredGarvin

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    It may be "wasted" from an electrical point of view, from a mechanical view to keep the plunger/valve it is connected to in the desired position then that power is not really wasted.
     
  8. Jun 10, 2005 #7
    Alot of people make this misconception. I can hold the plunger in place just as easily by running a pin through it to hold it in place and expend absolutely NO power whatsoever. The advantage is simply one of convenience. The power IS in fact wasted.
     
  9. Jun 10, 2005 #8

    FredGarvin

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    You can't always do that when the solenoid is unaccessible for whatever reason.
     
  10. Jun 10, 2005 #9
    True, but the point still is that no actual work is being done.
     
  11. Jun 12, 2005 #10

    FredGarvin

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    That is indeed true. I was looking at it from a broader sense, not the absolute definition. If I have a solenoid that is a power to open, so as to supply fuel to an engine that is doing work, can I really say that the power to hold the solenoid is being wasted? From the system involving the solenoid alone then I would say yes. It's just something I always get hung up on.
     
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