Question 422Electricity & Electronics - QMED

The correct answer is D) an open in the rotor field circuit. If the generator's rotor field circuit is open, it will result in a failure to produce voltage. The rotor field circuit provides the necessary electromagnetic field to induce voltage in the generator's stator windings. An open in this circuit interrupts the field and prevents voltage generation. The other options are incorrect because: A) a rotating slip ring is not related to voltage generation, B) brushes shifting out of the neutral plane would affect commutation but not necessarily stop voltage production, and C) excessive locked-rotor current is more related to a short circuit condition, not an open circuit.