Thread: Why 28V DC?
View Single Post
  #5  
Old January 14th 04, 05:08 PM
Todd Pattist
external usenet poster
 
Posts: n/a
Default

Jim Weir wrote:

And the inquisitive student might ask, if 24/28 was so good, why not go 3 in
series and get 36 volt systems...or like the phone company with 4 in series for
48 volts? Because, grasshopper, the calculation WAS made to find out the most
efficient combination of voltage/current/wire size and at the time (WWII) it
came out just shy of 30 volts. Rather than dick around with special 30 volt (15
cell) batteries, the decision was made to use off-the-shelf dual 12 or single 24
volt "industrial" batteries.


And since WWII the calculation has shifted, so you now find
cars being designed for 36 or 48 volts. The reason is still
cost/weight/size of wiring. When you want lots of power,
and don't want heavy/expensive/fat copper wiring you want a
higher voltage. Engines are being sold with valves that are
lifted by electromechanical actuators instead of mechanical
cams. The designers would go to even higher voltage if not
for fear that the mechanics/owners out there who're only
familiar with 12/24 volt systems in vehicles would be
electrocuted.

Todd Pattist
(Remove DONTSPAMME from address to email reply.)
___
Make a commitment to learn something from every flight.
Share what you learn.