Refer to the two-generator, two-motor, DC...

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Question 1 of 2066636eed28f7522a1c51d980

Refer to the two-generator, two-motor, DC diesel-electric drive propulsion system simplified schematic shown in the illustration. Which of the following conditions would cause the propulsion shaft to only rotate in the ahead direction? Illustration EL-0141

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Question 1 of 20

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🔍 Key Concepts

• Direction of rotation in DC motors depends on the relationship between armature current direction and field polarity. • In this system, note which rectifier (controlled vs non-controlled) feeds the generator fields and which affects the motor fields. • Consider how reversing is normally achieved in diesel-electric propulsion: by changing field polarity rather than reversing diesel engine rotation.

💭 Think About

• From the schematic, trace the power path from the main propulsion diesel-generators through the rectifiers to the DC propulsion motors. Which component actually determines the direction of current in the motor fields? • Ask yourself: if the prime movers (diesel engines) kept the same direction, could the electrical system alone still produce astern rotation by changing field connections? • For each failure option, decide: would that failure (a) lock the field polarity in one direction, or (b) just prevent speed/voltage control without fixing the rotation to ahead only?

✅ Before You Answer

• Verify which device labeled in the diagram as controlled rectifier is connected to the generator field circuits, and which device labeled non-controlled rectifier is tied to the motor field rheostats. • Confirm how a reversal of shaft direction is normally accomplished in this particular diagram: by changing polarity to the motor field or to the generator field? • Before choosing, rule out any option that does not directly affect the ability to reverse current (polarity) in the propulsion motor field windings.

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