Using resistor and DC motor acting as generator as a brake

  1. Apr 27, 2014 #1
    how would you calculate the resistance required for a resistor which is in series with a generator (DC motor in reverse) to achieve a certain torque from the generator?
    Eg, theres a torque of 30kN acting on a 100kW generator while it moves at 50RPM.
    The is the same mechanism as electric diesel locomotives use to brake that employ rheostatic braking.
  2. jcsd
  3. Apr 27, 2014 #2

    Simon Bridge

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    You have to ask yourself how much work is being done to run the generator circuit.
  4. Apr 28, 2014 #3


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    If this is a real, practical problem then the motor would need to be a suitable one. Many motors will not work as generators, particularly not high power motors, with field windings.
    Your suggested 100kW generator is quite a meaty piece of kit.

    Note. If you want to calculate power (in Watts), as Simon B suggests, you will need to convert your RPM to angular velocity (and get your Torque in the right units, too - do you mean kNm?)
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