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Transformer Question

Discussion in 'General Electronics Discussion' started by Muhasaresa, Jun 27, 2012.

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  1. Muhasaresa

    Muhasaresa

    45
    2
    Jan 2, 2012
    Hello everyone!

    I have not learn about transformers yet but I know the basics of how they work. When I looked at the inner workings of one I found out that when it is not connected to a device e.g. a phone charger, one set of coils is sill connected to the mains :eek:.

    My questions:

    Why does this not heat up to very high temperatures and melt? and

    Even when the phone is NOT being charged, is power unnecessarily wasted through the first coils?

    Thanks for the help,
    Muhasaresa ---||---
     
  2. BobK

    BobK

    7,682
    1,688
    Jan 5, 2010
    The coil has an inductance that limits the AC current going through it just as resistance limits the DC current. But the current in an inductor is out of phase with the voltage, which means the product of the two is 0 (when averaged over a cycle) and no power is used. So the only power used when a transformer primary is connected to the mains is that of the current (limited by the inductance) being pushed through the DC Resistance of the coil. This is minimal.

    When you put a load on the secondary, current flows in that circuit and it changes the inductance and hence the current flow in the primary causing it to draw more power.

    So, yes, there is some power wasted when a transformer is plugged in but there is no load on the secondary, but it is much less power than is used when there is a load on the secondary.

    Bob
     
  3. Muhasaresa

    Muhasaresa

    45
    2
    Jan 2, 2012
    Thanks a lot Bob! I'll look into inductors in a bit more detail before learning about transformers :)

    Muhasaresa ---||---
     
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