Refer to the diagram of the AC turbo-electric...

Question 1 / 2066636eed28f7522a1c51d976

Question 1 of 2066636eed28f7522a1c51d976

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

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Question 1 of 20

66636eed28f7522a1c51d976

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🔍 Key Concepts

• Study how the reversing lever in the illustration energizes the F and R contactors feeding the main propulsion motor. • Notice that the AC propulsion motor in this system is reversed by changing the phase sequence with contactors, not by changing a DC field polarity or using a separate astern winding. • Think about which components are common to both ahead and astern, and which components are used only for astern operation.

💭 Think About

• If the propulsion motor runs smoothly from maneuvering to full ahead, what does that tell you about the condition of the turbine, generator, and main motor windings? • Looking at the diagram, when the lever is moved to ASTERN, which additional device(s) must operate compared to AHEAD, and what would happen if they did not operate? • Which choice describes a fault that would affect BOTH ahead and astern if it occurred, and which choice describes a fault that would affect ONLY astern? Use that to eliminate options.

✅ Before You Answer

• Verify on the diagram whether there is any separate astern winding shown for the propulsion motor. • Check which contactor(s) F or R are closed in the ahead position versus the astern position. • Confirm that the turbo‑alternator (T-G set) must rotate and generate AC power in the same way for both ahead and astern; only the reversing contactor arrangement changes the motor direction.

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Question 1 of 20

The reversing contactor (R) fails to pull in.

The AC propulsion motor field winding fails to reverse in polarity.

The AC propulsion motor has an open astern winding.

The turbine of the turbo-alternator fails to rotate in the astern direction.

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Question 1 / 2066636eed28f7522a1c51d976

Question 1 of 2066636eed28f7522a1c51d976

Back

Question 1 of 20

66636eed28f7522a1c51d976

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🔍 Key Concepts

💭 Think About

✅ Before You Answer

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