Question 476Electricity/Electronics - Assistant Engineer70% to pass
Refer to the diagram of the AC turbo-electric drive system as shown in the illustration. The propulsion motor operates from maneuvering speed to full ahead speed in the ahead direction. The propulsion motor will not operate at any speed in the astern direction. What is most likely the problem? Illustration EL-0142
AI Explanation
The correct answer is A) The reversing contactor (R) fails to pull in.
In an AC turbo-electric drive system, the propulsion motor operates from maneuvering speed to full ahead speed in the ahead direction. If the propulsion motor does not operate at any speed in the astern direction, the most likely problem is that the reversing contactor (R) fails to pull in. The reversing contactor is responsible for reversing the polarity of the motor's field winding to enable astern operation. If this contactor fails, the motor will not be able to operate in the astern direction.
The other options are incorrect because: B) The AC propulsion motor field winding failure would prevent operation in both ahead and astern directions, C) An open astern winding would prevent astern operation but not necessarily ahead operation, and D) Turbine failure would affect power generation but not the motor's ability to operate in the ahead direction.
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