Re: [PSUBS-MAILIST] RE: DC Motors

[Carsten Standfuss <Merlinsub@t-online.de>]

Hi Jay, goor idear but I am sorry, I have not the space for a 40kw AC-DC
MG setup. Also the efficency is with 0,9*0,9 = 0,81 not very hig.
Produce at input 40 kwh just 32,4 kw power and 7,6 kw of heat.. 

best regards Carsten - but is my second option if the black box
Dc400v-Dc600v-Ac400V 0,95% box development fails.. 

Jay K. Jeffries schrieb:
> 
> Carsten,
> You might consider a motor-generator (MG) setup...a linked combo of a DC
> unit that can operate as a motor or generator and a AC unit that can operate
> as a motor or generator.  These were used on older diesel boats to generate
> the high voltage and or frequency required to operate some electronics.  On
> present day nuclear subs, the MG resides between the steam turbine
> generators (SSTG) and the batteries.  When charging the batteries, the AC
> unit is a motor and the DC unit the generator.  When drawing power from the
> batteries, the DC unit is the motor and the AC unit the generator.  Under
> normal ship's electrical load with the SSTG on line, the MG set would be
> slowly discharging the batteries to keep them in condition.  On a loss of
> SSTG power, the MG sets convert the DC power to AC.  The system was aligned
> in a port & starboard cross connected system for redundancy.  I'll try to
> lay out an ASCII schematic; the "X" indicate isolation switches for spitting
> systems or isolating faulty components/wiring:
> 
>  (DC load side)    (AC load side)
>           _____ MG ____X______ SSTG
>          |                 |
>          X                 |
>          |                 |
> BATTERIES                  X (normally open)
>          |                 |
>          X                 |
>          |_____ MG ____X___|__ SSTG
> 
> Your boat could be wired in a similar manner where the diesel generator is
> substituted for the SSTG.  Your main motor(s) could then utilize the
> efficiency of using high voltage and lower amperage units.
> Respectfully,
> Jay K. Jeffries
> 
> Hi Stephen I got this way an run in trouble..
> On euronaut I build a 400 V 40 kw DC Motor in - and use them as motor
> underwater and generator on the surface - direct to the 400 V DC
> batteries. That was the idear - But first highpower Dc technologies is
> old technologies and not so much parts are available anymore.
> 
> The real trouble beginns when you realise that both  bilge Pumps have
> 400 V AC - both compressors have 400 V AC and other subsystem like
> chargers etzc also.
> 
> The converter to make from 400 V Dc just 400 volt AC ist not off the
> shelf..  To make 400 AC you need at least a DC Voltage of 600 Volt..
> So I need now a highpower DC-Dcconverter which make from 350-450 V DC a
> 600-700 V DC and than a DC-Ac converter to make 400 V 3-phase AC..
> 
> Maybe it is easier to go with a AC system today.
> 
> Make shure that you have all your subsystem on your list before you
> decide which way your go. To rebuild all subsystem back from AC to DC
> will be a nightmare.
> 
> 48 V DC for a 75 kw output are very, very strong cables..
> 
> 75000 watt / 48 V = 1563 ampere..
> 
> best regards Carsten
> 
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