[QUOTE=cappy208;57146]MSCV:
It depends on the type of vessel you are discussing.
Typically a vessel will have several independent means of generating its own electrical power.
The larger the vessel, the more redundant, and efficient the systems become.
On a small tug or supply vessel the generators are usually diesel driven. Two, three or four separate generators, used in varying combinations depending upon electrical load and generator capability. Some generators are of different sizes, to efficiently accommodate differing loads. So by using them in different combinations you can match the load to the generators. This make for more efficient supply (both fuel wise, and hours on engines being run unnecessarily.)
Some vessels have ‘Shaft Generators.’ These scavenge some (usually a negligible amount) of the main engine shaft horsepower (KW) BUT, shaft generators are just used when underway, on sea voyages.
Shaft Generators are typically NOT used when in maneuvering situations because a shaft driven generator will be varying in output a little bit (as the engine speed is regulated during use) so to keep the electrical power at a constant level (cycle and voltage wise) to ensure expensive electrical components don’t get blown up, fried or smoked a standalone generator is used. On some older ships that have electrical components that are not that critical in voltage they do use shaft generators almost all the time when underway. But most modern ships have super sensitive equipment, engines, motors, pumps, and refer equipment that they need exact electrical supply.
Shaft gens also are only usable on constant speed engines, which use CP technology, to keep the shaft at a constant speed, and vary propulsion using the hub gears.
When is your research paper due? How much time do you have to do your own research?[/QUOTE]
Not entirely accurate. My vessel has two shaft generators and three house generators. Both shaft generators and two of the house generators are online during ALL maneuvering situations, with the mains running in constant speed mode. The house gens are 480v and the shafts are 6600v. The shaft generators provide all power to the thrusters and the winches. We also have the capability through a transformer to step up our 480 to 6600 or step down the 6600 to 480. So we can run everything off of the shaft generators or some of the thrusters and winch pumps off of the house generators. Our sister ship (which is 7 years older than us) does not have this capability and must run a main engine and shaft generator at the dock to run their winches. My vessel is state of the art, CPP propulsion, and < two years old. That being said the push seems to be towards diesel-electric and azimuth propulsion in a lot of applications.