Why 28V DC?

On 2004-01-14 10:34:04 -0800, "Charlie" said:

Jim Weir wrote an interesting response to the subject, then added,
"Then
there is the 115v 3ph 400Hz. discussion..."

Let's hear it!

Possibly because AC is a more efficient distribution technique that DC
for
long runs in large aircraft ? And 400Hz instead of 60Hz allows for
smaller
transformers to step down the voltage ? Just guessing here.

All of the gyros in the plane I fly (Lear 35) are powered by 400 Hz AC.
The inverters aren't more than 30 feet away. There are two transformers
(one on each bus) to provide 26 volts for the oil pressure guages, RMIs,
nav radios, and a few other things.

Back in my navy nuclear power days, I knew the reason for three phases. I
think it has something to do with power density - smaller, lighter, cheaper
is the AC mantra. Anyway.... 400 Hz provides higher power density and is
much cleaner than 60 Hz.

Am I on the right track?

--
Larry Fransson
Seattle, WA