Redundancy. If you have four shafts and four engines propelling them, they have to be four large engines, and if one fails, no way to turn that shaft at all. If you have four shafts and four large electric motors propelling them, and nine diesel power plants providing electricity for those four motors, and lose one power plant, you still have 8/9 of your power, and can still run all four shafts. (The Queen Mary 2 is an example of this.)
Carleton
-------------- Original message --------------
From: "Stephen Humphreys" <[EMAIL PROTECTED]>
> >Just like train locomotives, the large diesel engines on these ships drive
> >generators, which in turn power electric motors, to which are attached the
> >propellers.
> >
>
> In just one sentence (because its off topic) can you, or anyone, explain to
> a non-engineering type like me why the diesel engines power the electric
> motors that power the means of propulsion rather than cut the middle man out
> and have the diesel engine power the means of propulsion?
>
