How does voltage push current if they are flowing through seperate conductors?

Discussion in 'General Electronics Chat' started by DkEnrgyFrk, Apr 17, 2010.

  1. DkEnrgyFrk

    Thread Starter New Member

    Feb 15, 2010
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    I noticed that the diagram of the inside of transformer rated electric meter and circuit showed that the voltage and current are traveling along seperate paths. That the voltage is coming from a voltage transformer and that the current is coming from the current transformer. They will travel into the meter and out of the meter but will never make contact.
    As I understand it, voltage pushes current. But in this scenario they are not in the same line at any point past the step-down transformers.

    How does this work? How does the current still travel through the meter when it is seperated from the voltage like that?

    This is in the U.S. with a 240 - 120 step-down voltage transformer and a 40 - 1 step-down current transformer.
     
  2. Markd77

    Senior Member

    Sep 7, 2009
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  3. Wendy

    Moderator

    Mar 24, 2008
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    Basically electricity is created when a wire moves through a magnetic field. A transformer turns this on its head, the magnetic field moves through the wire.

    Counter EMF (the magnetic field created by the current flowing though the secondary) makes a transformer extremely efficient.
     
  4. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    Current transformers [CT's] and voltage transformers [VT's] are routinely used in many applications including electric power metering devices such as you mentioned.

    In that particular application the reasons for using CT's & VT's includes reducing the current & voltage levels to galvanically isolated values of safe magnitudes for use in the metering task. Trying to deal with an input voltage level of 100 Volts is a lot easier than 20,000 Volts - ditto for a current of 5A versus 1000A.

    Your question about voltage pushing current is a valid one. In the case of the metering system the CT primary is effectively connected in series with the power supply line conductors and the VT primary is connected in parallel with line &/or neutral conductors.

    As long as the transformed low side voltage and current parameters maintain a well defined linear relationship to the high power side parameters they can be used to provide instrumented indications proportional to the actual current, voltage & power values. The difference is only a matter of magnitude scaling.
     
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