Using resistor and DC motor acting as generator as a brake

  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. Simon Bridge

    Simon Bridge 15,478
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    Homework Helper
    Gold Member

    You have to ask yourself how much work is being done to run the generator circuit.
  4. sophiecentaur

    sophiecentaur 14,730
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    Gold Member

    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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