Question 558Electricity & Electronics - Assistant Engineer

The correct answer is D) reversing the phase sequence supplied to the motor. In an AC diesel-electric propulsion system, the main shaft rotation is reversed by changing the phase sequence of the AC power supplied to the electric propulsion motor. Reversing the phase sequence reverses the direction of the rotating magnetic field in the motor, which in turn reverses the direction of the shaft rotation. This is the standard method for reversing the propeller rotation in this type of propulsion system. The other options are incorrect because they do not directly reverse the motor's rotation. Reversing the prime mover rotation (option A) would not reverse the motor's rotation, and changing the generator frequency (options B and C) would only change the motor's speed, not the direction.