Re: Electric Drive and COGAD

In article <Xns9B748E915815752703703acsicom@xxxxxxxxxxxx>,
"scott s." <75270_3703a@xxxxxxxx> wrote:

Dennis <tsalagi18NOSPAM@xxxxxxxxxxx> wrote in
news:Xns9B72F4132C45EtsalagiNOSPAMasusnet@xxxxxxxxxxx:

What are the problems with using electric drive on a
surface ship?
In general, water and electricity don't mix well, but technology may
well have dealt with that; electric drive has long been used on
submarines. You have a weight penalty, but I don't think it's too
bad. What are the other drawbacks?

I think the problem has been efficiency of DC drive motors as used in
past surface designs. The idea now is to use AC drives, but to do that
you need to be able to handle high power, variable frequency AC.

At one time the only component that could do that was SCRs. But today
I think there are better options.

scott s.
.

There is good and bad of using electric drive...

Good -

1) removal of reduction gears (e.g. the transmission)
2) Shorter shaft lengths
3) More precise speed control
4) Faster reversing
5) lower crew size
6) the ability to move the engineering spaces around on the ship -
moving the larger spaces higher - above the water line
7) ability to increase the number of water tight compartments
8) ability to minimize heat signatures
9) reduction in piping in the ship
10) ability to use one set of engines for both weapons systems and
propulsion
11) ability to size engines better for maximum fuel efficiency (e.g. 6
to 10 diesels instead of 1 gas turbine)
12) ability to run the engines at a more efficient speed

Bad -
1) Loss of energy in conversion to electric power and back
2) Increase in wiring on the ship
3) inability to fix key parts of the engineering systems with the ship's
company (OBTW - similar issues exist with gas turbines)
4) Water and electricity issues
5) Cost
6) lack of long term underway experience

To date the bad have out weighed the good in ship designs. There have
been a number of programs to look at electric drive and even super
conducting electric drive on surface ships - all are still in the R&D
phase.

OBTW - you can thank the various military services for the battery
technology that will eventually go in cars and trucks - since they
wanted to provide high density safe batteries for use in combat and even
on ships and submarines...Yet another military spin off.
.

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