dc generator theory

Discussion in 'Homework Help' started by vini_i, Nov 4, 2013.

  1. vini_i

    Thread Starter New Member

    Apr 19, 2010
    we are studying generators.

    ac generators make perfect sense. rotor windings are energies with dc via slip rings and when spun produce an alternating current in the stator. also this process can be reversed. if dc is applied to the stator and the rotor is spun then an alternating current is retrieved from the rotor windings via the slip rings.

    a basic dc generator also makes sense. dc is applied to the stator and when the rotor is spun direct current is retrieved from the rotor via the commutator. the commutator acts as mechanical rectifier.

    where i'm not sure is... if dc is applied to the rotor via the commutator and the rotor is spun what happens in the stator? will it make ac, dc, or nothing at all?
  2. MaxHeadRoom


    Jul 18, 2013
    What happens in the case of a DC motor when a DC is applied and a stator field is present? A DC voltage is generated which opposes the applied voltage.
    The armature will then generate a voltage that will run up to an rpm where the generated voltage will almost reach the applied voltage.
    In the case of a DC applied to a rotor with no applied field the residual magnetism acts as a field if the armature is spun the rotor will then accelerate and generate a field, the end result is a motor will then operate in a run away condition and possibly to destruction.
    This is why DC motors with wound fields have field loss detection.
    Last edited: Nov 4, 2013