Question 1 of 2707066636eed28f7522a1c51d3fe

By what common means is the speed of an AC propulsion motor on a diesel-electric propulsion ship controlled?

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Question 1 of 27070
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By what common means is the speed of an AC propulsion motor on a diesel-electric propulsion ship controlled?

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🔍 Key Concepts

• AC induction motors and how their speed relates to synchronous speed • The relationship between frequency (Hz) of the supply and motor speed • Why voltage is adjusted along with frequency in practical propulsion drives

💭 Think About

• Think about which electrical quantity directly determines the synchronous speed (RPM) of an AC motor for a given number of poles. • Consider what happens to motor torque and current if you only change voltage but keep frequency constant, or only change frequency but keep voltage constant. • Modern diesel-electric propulsion uses variable-speed drives; what do these typically control to vary motor speed efficiently and safely?

✅ Before You Answer

• Identify which option(s) involve changing frequency, since synchronous speed depends on supply frequency. • Check which method keeps the motor operating with an appropriate volts-per-hertz (V/Hz) ratio to avoid overheating or loss of torque. • Eliminate any choice that would be impractical or unsafe for a large AC propulsion motor in continuous service.