🔍 Key Concepts

• Diesel-electric propulsion: how the diesel-driven generator and the DC propulsion motor interact • Generator field excitation vs motor field excitation: which one mainly determines the DC motor’s speed in a diesel‑electric system • Basic DC motor speed formula in relation to voltage and field strength

💭 Think About

• In a DC diesel-electric drive, which component actually supplies the adjustable voltage to the propulsion motor? • For a DC motor, does speed normally depend more directly on the applied armature voltage or on the prime mover (diesel engine) RPM in this type of system? • Which part is easier and more practical to vary smoothly under load: the diesel engine speed, the motor field, or the generator field?

✅ Before You Answer

• Remember that in diesel‑electric systems the diesel engine usually runs at a relatively constant speed for best efficiency and frequency control • For a DC motor, speed is approximately proportional to applied voltage and inversely proportional to field flux—consider which control method is typically used in propulsion • Verify which control method would allow smooth, wide‑range speed adjustment without frequently changing engine RPM or reversing polarity