Question 173Electricity & Electronics - Assistant Engineer

The correct answer is B) An open shunt-field circuit. In a self-excited DC generator, the shunt field winding is responsible for providing the necessary magnetic field to induce the output voltage. If the shunt field circuit is open, there will be no current flowing through the field winding, and the generator will not be able to build up the necessary magnetic field to generate an output voltage, even when running at the rated speed. The other options are incorrect because: A) Excessive residual magnetism would not prevent the generator from building up voltage. C) Excessive brush pressure would not cause a loss of output voltage. D) A shorted shunt-field circuit would not prevent the generator from producing an output voltage.