REFLECTOR: 24 volts vs. 12 volts

[Ron Brown]

By the way, isn't the voltage out put from a 12v alternator dependant on the voltage regulator?

The reason I ask this, is that a friend's 172 has a 24v system, but the installed alternator was a 12v alternator and it was charging the 24v system just fine.  The voltage is a function of the voltage regulator.  I believe an alternator can put out close to 100 volts or more if the field voltage is continued to be applied.  I doubt there is much different between a 12v and 24v alternator other than the name plate.  

But, I agree, the 12 volt system is lower cost if not a bit heavier (only a very few pounds) - eat fewer cheeseburgers!

Ronnie 
  ----- Original Message ----- 
  From: Al Gietzen 
  To: Jim_Agnew_2 at yahoo.com ; 'Velocity Aircraft Owners and Builders list' 
  Sent: Monday, January 24, 2005 12:25 PM
  Subject: RE: REFLECTOR: 24 volts vs. 12 volts






  Not true, an alternator requires cooling for the heat produced in direct

  relationship to the watts produced.  12V x 50A = 600 watts = 24V x 25A.  If you

  have the same amperage output at 24V you have a 120W alternator.



  Jim



  I think the cooling is not a function of watts out, but of the watts of loss in the windings; I^2 x R.  I don't know what all else changes in the alt design for 24v, like number of windings; but I'd expect to get more output power from a 24v setup than for 12v for the same cooling requirement.



  Al



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