Question 260Electricity & Electronics - 1st Asst/Chief

The correct answer is B) varying the input frequency of the voltage to the motor. The speed of a synchronous AC propulsion motor is directly proportional to the frequency of the voltage applied to the motor. By varying the input frequency of the voltage, the speed of the motor can be controlled. This is a common method used in diesel-electric propulsion systems to control the speed of the propulsion motor. The other options are incorrect because: A) increasing the current would not directly control the motor speed, C) decreasing the motor voltage would actually reduce the speed, and D) increasing the motor voltage would not directly control the speed.