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Alternator capacity

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tomcostanza

Joined: 19 Oct 2008
Posts: 49

Posted: Sat Nov 08, 2008 6:07 am Post subject: Alternator capacity

Hi all,



What should I consider when I calculate the capacity of an alternator?  I've read Bob's posts about never seeing a situation that couldn't be served by a 40A unit.  But if I just add the requirements of each item, I get closer to 60A.  Should I consider things like landing/taxi lights (I have 4 bulbs (at) 6.5A each), or count them as zero (since they will only be used for a few minutes before, during, and after landing)?  What else am I missing?



Thanks.

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_________________
Clear Skies,
Tom Costanza
-- in year 17 of a 3 year project

nuckolls.bob(at)cox.net
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Posted: Sun Nov 09, 2008 5:55 am Post subject: Alternator capacity

At 06:07 AM 11/8/2008 -0800, you wrote:

 	  Quote: 	
		  

<Tom(at)CostanzaAndAssociates.com>



Hi all,



What should I consider when I calculate the capacity of an 

alternator?  I've read Bob's posts about never seeing a situation that 

couldn't be served by a 40A unit.  But if I just add the requirements of 

each item, I get closer to 60A.  Should I consider things like 

landing/taxi lights (I have 4 bulbs (at) 6.5A each), or count them as zero 

(since they will only be used for a few minutes before, during, and after 

landing)?  What else am I missing?


	


   If you used landing and taxi lights intermittently

   and for short periods of time, they do not become

   high-energy loads that beg for continuous support

   by the alternator. Do you use all four lights on

   at any one time?



   On my website at:



http://www.aeroelectric.com/PPS/Load_Analysis/



   you will find a number of exemplar spread

   sheets where members have conducted their

   own detailed load analysis. You can take

   one of these and consider it for how changes

   to match your airplane would give you a clearer

   picture of your operational energy requirements.

   There is also a blank form at:



http://www.aeroelectric.com/PPS/Load_Analysis/Blank_Form.pdf

   I use this format as the index page to my

   wire-book products where the load analysis

   becomes a list of all electrical sub-systems

   in the airplane, indexes the page were wiring

   for that sub-system can be found in the wire-book,

   and discusses energy requirements for each

   sub-system depending on how and when it is

   used in the operation of the airplane. An

   exemplar work-in-progress can be seen here:



http://www.aeroelectric.com/Reference_Docs/Misc_PDF/N820JPWB.pdf



   Depending on how and in what combinations you

   operate appliances in your aircraft, you may well

   find that a 40A alternator has the necessary

   overhead to run all needed equipment while holding

   10A or so in reserve for the purpose of recharging

   a battery.



   Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------

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