Question 62Electricity & Electronics - 1st Asst/Chief

The correct answer is B) The field winding of one of the propulsion generators is open-circuited. The reasoning is that in a two-generator, two-motor DC diesel-electric drive system, the speed of the propulsion shaft is directly proportional to the voltage generated by the propulsion generators. If the field winding of one of the generators is open-circuited, it will result in a reduction of the generated voltage, which in turn will cause the propulsion shaft speed to be approximately one-half the desired speed. The other options are incorrect because an open-circuit in the armature winding of a generator or the field or armature winding of a motor would not necessarily result in a 50% reduction in propulsion shaft speed. These faults would likely cause other issues, such as loss of power or unbalanced operation, but not necessarily a 50% speed reduction.