Question 259Electricity & Electronics - 1st Asst/Chief

The correct answer is A) by varying the input frequency of the voltage to the motor. On a diesel-electric propulsion ship, the speed of the AC propulsion motor is typically controlled by varying the frequency of the voltage supplied to the motor. This allows for smooth and efficient control of the motor's speed without the need to adjust the motor voltage or current directly. Varying the frequency is a common and effective way to control the speed of AC motors in marine applications. The other options are incorrect because: B) decreasing the motor voltage would not provide as precise control, C) increasing the current to the motor would not directly control the speed, and D) increasing the motor voltage would not be the primary means of speed control for this type of propulsion system.