Question:

If a household uses less electricity, does the transformer on the utility pole actually draw less current?

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I've read about how the transformer that steps the high voltage power from the utility power lines down to the meager 240 volts that a house uses and I've seen the diagram, and from what i can see, it looks like there is an unregualted coil that high-voltage electricity constantly flows through. If I stop drawing from the smaller, low voltage output coil, how would that effect how much power continues to travel through the first coil? Is there regulatory circuitry in the transformer to regulate this coil's current, or does it just keep flowing? It would seem like it must be regualted, because the utility system can be overloaded, resulting in a blackout, so the draw must not be constant. So how does it work?

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3 ANSWERS


  1. you are confused on how transformers work. If you don't draw any current from the secondary, there is no current in the primary, aside from a small number due to losses in the transformer.


  2. your thinking backwords any thing that uses electricity pulls the current so the answer is yes.

  3. Yes, the transformer on the utility pole actually draws less current when the household loads draw less current. Yes, there is a regulatory circuit in the transformer that regulates the current in the primary so that it changes when the secondary (household) current changes so that the ratio of primary current to secondary current is always maintained at the inverse of the ratio of primary voltage to secondary voltage.

    The regulatory circuit or mechanism is actually part the magnetic circuit of the transformer. When the load current increases, the current in the secondary winding tends to create a magnetic field that would oppose the magnetic field of the primary winding. The primary winding compensates for the opposing force by increasing current to balance the secondary current and maintain the magnetic field at just the magnetizing field that is created by the small current that flows in the primary when there is no load on the secondary.

    You will find this explained in various ways in engineering text books and in Wikipedia with diagrams, mathematics and additional details.

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