Question 246Electricity/Electronics - 1st Asst/Chief70% to pass
How is the main propeller shaft rotation of a conventional AC turbo-electric drive normally reversed? (Assume that no converters or inverters are used.)
AI Explanation
The correct answer is C) reversing the phase sequence applied to the AC propulsion motor.
In a conventional AC turbo-electric drive system, the main propeller shaft rotation is normally reversed by reversing the phase sequence applied to the AC propulsion motor. This changes the direction of the rotating magnetic field within the motor, which in turn reverses the direction of the propeller shaft rotation. Reversing the field polarity of the AC propulsion motor (option A) or generator (option B) would not achieve the desired reversal of rotation. Option D, reversing the steam turbine direction, is also incorrect as it does not directly impact the propeller shaft rotation in an AC turbo-electric drive system.
Related Questions
#244 The design Power Factor (PF) of a vessel's electrical system is generally 0.8 - 0.9. The system's greatest load is inductive. One notices a slow, gradual decrease, over time, in the PF, from normal/design. What can one do on board to maintain the normal, design PF and thus maintain electrical system's efficiency? #245 You direct the electrician to take quarterly insulation resistance reading of the ship's critical motors. What additional directions would you give to ensure accurate readings are taken that will allow for the logical comparison of prior and current readings? #247 How is the main shaft rotation on an AC diesel-electric propulsion vessel normally reversed? #248 Which of the listed ranges represents the specific gravity for the electrolyte of a fully charged lead-acid battery at room temperature? #249 What should be performed as routine maintenance of lead acid batteries?