🔍 Key Concepts

• Look closely at the symbols next to the main propulsion diesel generators and the two generators feeding the propulsion armature loop in illustration EL-0141. • Review how DC generators normally control output voltage (compare changing speed vs changing field strength). • Recall how polarity reversal is usually achieved in a DC system supplying propulsion motors (field polarity vs armature rotation).

💭 Think About

• From the illustration, decide whether the main propulsion generators are producing DC or AC by examining the component symbols and rectifiers shown. • Ask yourself: what part of the generator is being fed from the controlled rectifiers above each main engine, and what does that tell you about how voltage and polarity are controlled? • Consider which method of reversing direction is practical on a large diesel‑electric propulsion plant: physically reversing rotation, or switching electrical polarity.

✅ Before You Answer

• Verify from the diagram whether any rectifiers are between the generators and the propulsion motors, and what that implies about AC vs DC output. • Confirm what is labeled as Generator Field in the diagram and how it is supplied (variable and reversible?). • Before choosing, be sure you can state in your own words: "These generators are ___ type, their voltage is controlled by ___, and their polarity/direction is reversed by ___."