Impedance transformers

Discussion in 'General Electronics Chat' started by DrNick, Feb 20, 2007.

  1. DrNick

    Thread Starter Active Member

    Dec 13, 2006
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    Has anyone here ever built an impedance transformer that reflects real power and allows the imaginary to pass? I heard that the energy bill for a high power device at MIT was costing them too much money, so they put an impedance transformer in front of it, and reduced their energy bill significantly (because energy companies do not bill for imaginary power!!! heh)
     
  2. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    And they frown upon someone delibertly changing the power factor.

    If MIT is involved in a theft of service, it would be news, and in the Massechuettes court system.
     
  3. DrNick

    Thread Starter Active Member

    Dec 13, 2006
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    So the power company considers it theaft to use energy they dont bill for? Do they say that you can't change the power factor when you sign up for service?
     
  4. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    I think it is not theft, because you can connect anything you want after the clock, if it meets some electrical requirements and is installed by some professional.

    But is it possible to get purely inductive or capacitive load using some transformer?

    Let's say I have a resistive heater connected to single phase. How would the circuit look like, which will transform it to reactive load?
     
  5. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    Don't you think the electric company would investigate why a customer who spent alot of money for their service and suddenly is spending a little would investigate the cause of the drop?

    If they were going to say that much, why not install their own 1kW generator and run the 1 MW plant from this "imaginary" power.
     
  6. DrNick

    Thread Starter Active Member

    Dec 13, 2006
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    Well the thing is that I believe that this reflects the real power, so you can't run a larger generater from a smaller one. It just uses power that the energy company doesn't bill for. I am playing around with matching networks for now to see if I can get one of these bad boys working heh.
     
  7. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    I have a feeling it would have to be active, like power factor correction for PSUs.
     
  8. Papabravo

    Expert

    Feb 24, 2006
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    AFAIK there is no such thing as imaginary power. There is power factor correction but that just means bringing the voltage and current to the same phase. When you do this, the cosine of the phase difference is one and the instantaneous power is V times I. At any other phase difference the cosine will be less than 1 and the power will be less than the power delivered in the matched case which represents a purely resistive load.

    I think you are wasting your time and if you're not careful may be a candidate for a Darwin.

    Although not entirely clear you might find the following helpful
    http://en.wikipedia.org/wiki/Apparent_power
    http://en.wikipedia.org/wiki/Electricity_meter
     
  9. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Yes, but there is imaginary current, eg. out of phase with voltage.
    And the initial thought was probably about imaginary current and not power.

    It is possible to create power factor correction which will make the cosine 0, but I think the device will never pay back, because for industry it is impossible to use it because off sudden consumption drop.
    And for home like for heating it is also unusable, because making corrector for tenths of kilowatts is not a thing for a DIYer.
     
  10. Papabravo

    Expert

    Feb 24, 2006
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    I'd be careful. Just because you can represent an AC wavform with a complex number does not mean there is an imaginary current. All currents a real just as all voltages are real.

    The magnitude and phase of an actual waveform behave the same way as the phasor quantity, but that does not mean that the current or any component of the current is imaginary.
     
  11. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    ok I am using wrong terms, but you know what I mean and thats the point.
     
  12. Papabravo

    Expert

    Feb 24, 2006
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    I don't worry about thee and me but some of the other folks may be unclear on the thrust of the discussion.
     
  13. thingmaker3

    Retired Moderator

    May 16, 2005
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    What they do say when you sign up for service is that they will bill more if the power factor is below a certain level. TANSTAAFL. ;)
     
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