Question 60Electricity & Electronics - 1st Asst/Chief

The correct answer is C) A failure of the controlled rectifier to reverse polarity to the generator field windings. In a DC diesel-electric drive propulsion system, the controlled rectifier is responsible for reversing the polarity of the generator field windings, which in turn reverses the direction of the generator output and ultimately the direction of the propulsion shaft. If the controlled rectifier fails to reverse the polarity, the generator output will remain in the same direction, preventing the propulsion shaft from rotating in the reverse direction. The other options are incorrect because they do not directly impact the ability to reverse the direction of the propulsion shaft. A failure of the main propulsion diesel generators engines (A) or the field rheostats (B) would not prevent the controlled rectifier from reversing the polarity, and a failure of the non-controlled rectifier (D) would not affect the generator field windings.