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RE: [PSUBS-MAILIST] diesel electric
Can you use a small inverter at each device?
--- MerlinSub@t-online.de wrote:
> To run a AC-Motor from a DC battery needs a special
> frequency drive
> which can handle the high difference in voltage
> between nearly empty
> and full DC battery.
>
> For example :
> DC battery empty = 344 Volt
> DC battery full = 400 volt
>
> Most frequency drives are programmed that way that
> the quit if
> voltage is 10% lower than nominal Voltage.. 400 -40
> V = 360 Volt
>
> My problem is that I have a DC-Motor/Generator which
> load and run
> from the DC battery - no problem - but all the
> secondary system like
> air compressors and bildge pumps runs on AC.. so I
> need a AC- Network
> This required a frequency converter - and this seems
> is not off the shelf.
>
> There seems some available in the e-car market, the
> UPS-market
> and the solar-energy market which can handle that..
>
> regards Carsten
>
>
> "Stephen Pearce" <sjpearceqld@bigpond.com> schrieb:
> > Frank
> >
> > Without getting in to a Pissing competition I will
> quote my friend who
> > is an electrical engineer "the motor (AC) that has
> been selected will
> > handle full load at all speeds, yes without using
> braking
> > resistor/dynamic braking." I am not an expert but
> I have consulted
> > several and not one has suggested a DC system in
> practice will be
> > practical without manufacturing a Customised
> purpose specific motor like
> > in conventional military subs.
> >
> > If you are talking about small DC motors like on
> the K boats or Kara
> > then DC is the way to go. The size of the sub
> Brian has on the drawing
> > board he will need a 600+ Volts DC for the system
> to work. That's a lot
> > of 2 volt Cells or even 12 or 24 volt cells. Ask
> Carsten, I believe
> > several months ago he was making substantial
> modifications and now
> > requires 600 Volts because of his choice to go DC
> and had not yet
> > concluded the make up of his final system.
> >
> > The problems and expense of a 600Volt system and
> the cost of the
> > switching and associated components are huge. For
> example a 75KW DC
> > motor is in the range of 28K to 30K (USD) new. The
> AC equivalent is
> > about 12K and Reconditioned about 6K.
> >
> > I would also fell less comfortable in a vessel
> with a 600V DC system
> > that under certain circumstances may be subject to
> partial flooding. You
> > will need room to house all those batteries in
> water and air tight
> > 'spark free' containers.
> >
> > By all means run your hotel load off 12V DC
> batteries but DC setups for
> > 50+ HP can be impractical and cost much more in
> real terms. I went
> > through this process with the initial view of
> wanting a DC only system
> > but I have modified my design as a result of being
> prepared to accept
> > that there are experts with experience in this
> area that know more than
> > I do. I want a successful P-sub at the end of the
> process even if that
> > means that my initial design was impractical due
> to my ignorance.
> >
> > Frank if you can design a better propulsion system
> using 50+ volts DC
> > motors and Diesel Gensets that overcomes the
> problems and
> > impracticalities I have described I would be
> sincerely interested in
> > looking at it and if it is superior to my current
> design adopt it as my
> > system of choice.
> >
> > Respectfully (sorry Jay for borrowing your tag
> line :-) )
> >
> > Steve P
> >
> >
> >
> > -----Original Message-----
> > From: owner-personal_submersibles@psubs.org
> > [mailto:owner-personal_submersibles@psubs.org] On
> Behalf Of
> > ShellyDalg@aol.com
> > Sent: Wednesday, 1 November 2006 4:43 PM
> > To: personal_submersibles@psubs.org
> > Subject: Re: [PSUBS-MAILIST] diesel electric
> >
> > Just a quick note.... D.C. motors have more torque
> at lower speeds,
> > where the power band of an A.C. motor isn't
> realized until the optimum
> > speed of the particular A.C. motor is achieved.
> > The universal availability of A.C. components
> doesn't work either, when
> > you consider the use of different Hertz
> configurations in foreign
> > countries. D.C. is D.C......no matter what country
> you're in. Everybody
> > in the world uses 12 volt chargers.....and
> batteries the world around
> > are all compatible. My jumper cables built in
> Chicago, will connect to
> > my Toyota, carry a charge to my wife's Volvo,
> which will get us to my
> > broken down Harley out on Interstate 5, and
> getting me back home with
> > time to see Monday's game on my 12 volt T.V.
> > Stick to D.C. and save yourself a lot of expense
> and grief.
> > Frank D.
> >
>
>
>
>
>
>
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