While standing an "at sea watch" onboard an AC diesel-electric drive ship with a synchronous propulsion motor with the ability to vary the field excitation strength and still remain in synchronism. Ideally what would be the character of the power factor associated with the main power distribution system including all motors?
⢠Power factor and its meaning in AC electrical systems ⢠How synchronous motors can adjust reactive power by changing field excitation ⢠What an engineer ideally wants for the overall ship service power factor on a dieselâelectric vessel
⢠Think about what happens to power factor when a synchronous motor is overâexcited versus underâexcited. Which way (leading or lagging) does each condition push the system? ⢠If you can freely adjust the field excitation and still stay in synchronism, what power factor condition would you try to achieve for the entire main power distribution system to minimize current and losses? ⢠Among lagging, leading, zero, and unity power factor, which one is most desirable from the standpoint of generator loading and efficiency in normal operation?
⢠Be clear on the definition: power factor = real power (kW) / apparent power (kVA) and its maximum theoretical value ⢠Recall whether unity power factor means no reactive power flow, and how that compares to âpurely leadingâ or âpurely laggingâ conditions ⢠Verify which option corresponds to the most efficient and desirable normal operating condition for shipboard generators when you have the ability to trim excitation.
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