transforme output question

Discussion in 'General Electronics Chat' started by wes, Aug 24, 2007.

  1. wes

    Thread Starter Active Member

    Aug 24, 2007
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    Hi , i'm new and i have had this question for a long time mainly because i havent been able to test it so i was hoping someone could at least give it a shot, it would be really helpful. Well the question is what would happen if you were to be able to get a higher amount of power on the secondary then the primary, would the secondary start to act like the input or would the primary start to just decrease the amperage pull, well if anyone could atleast give me some help on it then it would be very helpful, thanks
     
  2. John Luciani

    Active Member

    Apr 3, 2007
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    You can not get more energy out than you put it. It violates the first law
    of Thermodynamics (conservation of Energy). If you think that you are getting more
    energy out you have not accounted for all the input energy sources.

    (* jcl *)
     
  3. recca02

    Senior Member

    Apr 2, 2007
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    do you mean what wud happen if a source was connected to primary?
    a lot depends upon what type of signal is applied and is it in phase with the primary. based on its phase relationship a current will start circulating in the windings which will heat the windings and this may even damage the transformer.
    both the emfs will try to create their own magnetic fields,right now its quite hard to exactly imagine what would happen as it also depends on many factors.
    does that answer any of your doubts?
     
  4. cb83

    Member

    Aug 9, 2007
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    Luciani is right. The secondary circuit draws it's power from the primary. If you try driving both the primary and secondary coils with a power source you'll just end up frying something, but the power lost in one coil will be the same as the power gained in the other (assuming a simple ideal 2 coil transformer).

    You can flip around your transformer (once again assuming a simple ideal 2 coil transformer) so that a 1:10 would then be a 10:1. A step up would then act as a step down. This isn't always possible in practice.
     
  5. recca02

    Senior Member

    Apr 2, 2007
    1,211
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    its not always necessary that the transformer will get damaged if you supply both sides with voltage source . but now that i read your post carefully maybe this wasnt what u intended to ask, but then isnt it obvious unless u add power from some external source the output will always be equal to (actually lesser due to losses) the input power.
     
  6. wes

    Thread Starter Active Member

    Aug 24, 2007
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    well what i was basically asking was say you did hook up a power source to both sides, but on the secondary the power source is just there to step up the power to power say some device that couldent be powered unless you put that extra power source on the secondary, and say you made sure the transformer secondary was capable of handling the amperage and voltage that would have been on the secondary due to the extra power source. would the more power on the secondary cause the primary to try and pull more amperage in
     
  7. Eduard Munteanu

    Active Member

    Sep 1, 2007
    86
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    Well, the other power supply will be DC (or it can be rectified). But DC shouldn't generate any EMF on the primary, so my guess is that no extra heating etc. occurs. Am I right?
     
  8. niftydog

    Active Member

    Jun 13, 2007
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    The amount of power passing through the primary side is entirely dependent on the voltage between the two terminals of the winding, surely!

    If you're mythical secondary supply caused the voltage on the primary to increase, then the power on the primary would go up. However, if it caused it to decrease then the power would go down. Whether it increases or decreases, and by how much, depends on the phase of the supplies being used and the turns ratio. But then you have the problem of determining the ratio of the contribution from each supply to the primary current.

    From the perspective of a DC supply a transformer is a short circuit, so not only would it not generate EMF it wouldn't even generate a voltage! Either it would blow a fuse or be shut down by the short circuit protection circuitry.
     
  9. wes

    Thread Starter Active Member

    Aug 24, 2007
    242
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    well eduard no it wouldnt be dc,it would be another ac source hooked in series with the transformer and to niftydog the phase would be a single pase 120 volt at 60Hz (or you could say it's a ac generator with a total wattage output of about 1000 watts) on the primary and the secondary would be say 480 volts on the transformer then connected in series to a 120 volt supply single phase 120 volt at 60 Hz supply(total watt rating of 1000 watts) so the total output voltage would be 600 volts and say the load was a 1800 watt motor or something?? The point is would the primary on the transformer try to increase the pull of power or would it just decrease the pull since there is more power on the secondary??

    Ikeep thinking the secondary would induce power back into the primary and then that could cause a problem with the generator by possibly slowing way way down although didsome tests with some dc motors (one generating ,he other powering) and when Iconnected them in series the generator increased speed. ??????? sorry about the grammer
     
  10. niftydog

    Active Member

    Jun 13, 2007
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    Well, my thinking is that the extra voltage supplied to the load would decrease the current required by the motor, hence reducing the current flowing in the secondary, which when combined with the current contribution of the secondary supply should reduce the demand on the primary supply.

    AC motor speed is dependent on the frequency of the supply, not the voltage. So your generator would not slow down if the voltage drooped, but it would loose torque. Furthermore, the speed of the AC motor (the load) would remain constant given that the frequency is fixed.
     
  11. wes

    Thread Starter Active Member

    Aug 24, 2007
    242
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    thanks niftydog
     
  12. wes

    Thread Starter Active Member

    Aug 24, 2007
    242
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    oh yea if that secondary current was also higher then the primary and the voltage was higher then what. would probably just start acting like the primary
     
  13. wes

    Thread Starter Active Member

    Aug 24, 2007
    242
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    thanks nifty dog and well if the current was higher then the primary as well as the voltage then what, would the secondary probably just start to act like the primary

    Ex. primary = 120V at 5A =600W
    Secondary = 600V at 10A =6,000W
    now the load(say 5 700Watt computers) requires 3,500 W total

    what then would secondary start inducing power back into the primary??
     
  14. niftydog

    Active Member

    Jun 13, 2007
    95
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    It all depends on the reflected impedance of the primary as seen from the secondary which, without some real numbers and proper circuit analysis, is an unknown quantity. Again, everything I've posted here is pure speculation - if you really want to know what happens then I suggest you'd need some mathematical analysis of the impedances in the system. Done correctly you could replace the transformer with impedances and carry out a circuit analysis.
     
  15. recca02

    Senior Member

    Apr 2, 2007
    1,211
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    this is what i think.
    since the voltage on secondary adds up to become larger than the primary
    the back emf due to it might increase as it creates more flux that supports the original flux in phase. this should increase the back emf on the primary. hence the back emf on the primary might become greater than the secondary voltage applied which might send a current in reverse direction to the primary magnetising current (this is all a guess, as opposite case happens when transformer is put on load) thus it might reduce the back emf.not sure though.
     
  16. wes

    Thread Starter Active Member

    Aug 24, 2007
    242
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    alright well thanks to everyone and if any of you were wondering on why I was asking it was because of a idea I had this had to do with overunity or more power output then input (I know it goes against the conservation of energy) and I have the circuit and everything designed but the transformer part kept bugging me, I need to test the idea but I dont have the money yet, LOL

    alright well thanks everyone
     
  17. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,157
    Can you show the circuit?
     
  18. wes

    Thread Starter Active Member

    Aug 24, 2007
    242
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    maybe one day, i'm still deciding on whether I want to patent it or whether to just go opensourece where everyone can see it but i'm still afraid someone will just steal it and say they made it ( which would suck and I would probably end up in prison, lmao), I did spend like 3 to 4 years working on it and I havent built it because of money for one and just wanting it to be perfect before I actually build it. So maybe one day but not yet, I mean I havent even built it yet,lol.

    well what do you think, patent or opensource(free) for everyone
    although I could patent it then give it away for free
     
  19. niftydog

    Active Member

    Jun 13, 2007
    95
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    The patent process is sometimes akin to hell on earth, so you'd want to be absolutely sure that it works before you go down that path.

    Frankly I'm with Scotty - "You canna change the laws of physics, captain!"
     
  20. wes

    Thread Starter Active Member

    Aug 24, 2007
    242
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    yeah, I have heard that to. i'm stiil thinking of differnt ways to try and cut the cost of it cuz it's to expensive to build for me right now. i've already spent alot on test's alone, it's something like $500 to $600 dollars and having school as well so it will be awhile before I can build it.

    thanks for all the help
     
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