Increasing the load resistance across one of the phases in a generator increases voltage out

Discussion in 'General Electronics Chat' started by Andymc12, Apr 23, 2019.

  1. Andymc12

    Thread Starter New Member

    Apr 23, 2019
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    I'm not completely clued up when it comes to hardware, but I feel I have a sound understanding when it comes to theory.
    I have a DC motor - AC generator configuration which provides a three phase output. For approximating the power output of the generator when a constant voltage is applied to the DC motor (10 V), I used several load resistances; specifically 10, 100, 1000 and 10000 ohms. What I found was quite baffling.
    To note, I have recently discovered that only one of the three phases represents a true sinusoidal waveform whilst the other two are heavily distorted.
    The phase which has the appearance of the traditional waveform was used for testing and each of the load resistances were placed across it. What I found was that as the resistances increased in value, the current through the resistance decreased, as expected, but the voltage drop across the load actually increased. Is there any feasible explanation for this because after three years in university i'm completely stumped by this finding.
    Thanks in advance.
     
  2. AlbertHall

    AAC Fanatic!

    Jun 4, 2014
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    Nearly all normal voltage sources behave in this way. When you operate the starter in your car and draw lots of current, the battery voltage falls. This happens because of the resistance (real or apparent) in series with the voltage source and some of the voltage is dropped across this resistance by the current flowing.
    http://tap.iop.org/electricity/emf/121/page_46054.html
     
  3. Andymc12

    Thread Starter New Member

    Apr 23, 2019
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    So am I right in saying that as the load increases and the current decreases, the voltage drop across the internal resistance decreases resulting in a higher voltage drop across the load?
     
  4. AlbertHall

    AAC Fanatic!

    Jun 4, 2014
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    Exactly.
     
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