Re: DC Voltages

From:         Chris Jardine <>
Organization: Wood County Telephone Company
Date:         20 May 96 10:13:17 
References:   1
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In Article<airliners.1996.668@ohare.Chicago.COM>, <> write:
> I have a question about the 28VDC used on commercial aircraft.  Are
> there any special or unusual characteristics about this current?  I
> have a need to take the 28VDC and convert it to 12VDC in an aircraft,
> any ideas?

	The first thing that we need to know is what the current requirements
would be for this project. If you need a major amount of current (like for a
starter motor, or anything in excess of about 30 Amps) you will be best to
gain access to the batteries as many times 28 volts is simply 2 batteries in
series and about 12V is available at a junction between the two batteries that
make the series combination. Anything less and you can usually use some sort
of voltage regulator system. It can be a linear pass regulator or a
chopping/switching system using a transformer and some other control, like in
your PC. It all depends on the minimum, normal, and maximum current load.
	Post a response and I'll see if I can make a recommendation. I am not
certified to do any work on aircraft and I really don't know if there are any
specific regulations reguarding any of my recommendations. I will say,
however, that I do have a degree in Electrical Engineering and should be able
to help.

Chris Jardine
CJ Electronics