Re: DC Voltages

From: (David T. Medin)
Organization: Rockwell Avionics - Collins, Cedar Rapids, IA
Date:         01 Jun 96 16:32:39 
References:   1 2 3
Followups:    1
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In article <airliners.1996.788@ohare.Chicago.COM>, Steve Lacker <> writes:
|> > wrote:
|> >>
|> >> 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?
|> >
|> There are numerous commercial DC-to-DC convertors available (we use the Vicor
|> brand extensively). These things are pretty remarkable in that they will
|> deliver a rock solid output voltage, even at their max rated current draw,
|> while the input voltage varies over a factor of 3 or more. They are also
|> amazingly compact.

I'll put another plug in for Vicor. The converters also use a 500 KHZ
to 1 MHz conversion frequency, so it is easier to filter out conducted
EMI. The radiated EMI from Vicor converters is almost nil. Efficiency
is upwards of 80%, so there is little heat. Application is real simple.

The original poster didn't mention what aircraft was the target for
the project. Make sure you check out the applicable FAA regs for
onboard appliances. In the case of air transport category aircraft
(most of which use 28 VDC for the battery bus), DO-160B is the most
common standard. This is apart from the STC you might need for

       David Medin            Phone: (319) 395-1862
   Rockwell Collins ATD	      Internet:
     Cedar Rapids, IA