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SD8 output at 28V?

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digidocs

Joined: 04 Dec 2013
Posts: 59

Posted: Mon Dec 22, 2014 10:49 am Post subject: SD8 output at 28V?

Hello Aeroelectric,



Does anyone have information about the SD8 output performance at 28V?



B&C are advertising a 28V version, but were unable to provide any data when I asked.



I also took Bob's 12.5V/13.8V output ratings at 3100 alternator RPM and built a Thevenin equivalent circuit.  That shows open circuit voltage of only ~20V.  Hopefully that's not an accurate way to model this device.



David

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nuckolls.bob(at)aeroelect
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Posted: Mon Dec 22, 2014 1:37 pm Post subject: SD8 output at 28V?

At 12:49 2014-12-22, you wrote:

 	  Quote: 	
		  



Hello Aeroelectric,



Does anyone have information about the SD8 output performance at 28V?



B&C are advertising a 28V version, but were unable to provide any 

data when I asked.



I also took Bob's 12.5V/13.8V output ratings at 3100 alternator RPM 

and built a Thevenin equivalent circuit.  That shows open circuit 

voltage of only ~20V.  Hopefully that's not an accurate way to model 

this device.



David


	


   Both 14 and 28v versions are wound by B&C. The

   28v version would have more turns on it than

   the 14v. The alternator's output is roughly

   limited by the magnetics. This is a 100W alternator

   frame so I would imagine that the 28v performance

   for current is 1/2 that of the 14v version.



   I'll be at B&C in then next few weeks . . .I'll

   check for sure.



   Bob . . .

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digidocs

Joined: 04 Dec 2013
Posts: 59

Posted: Mon Dec 22, 2014 1:52 pm Post subject: Re: SD8 output at 28V?

Bob,



That's really helpful information.  I currently have the 14V version and B&C told me that I could switch it to 28V by simply changing the regulator.  It sounds like that may not be the case.  (no pun intended)



David

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nuckolls.bob(at)aeroelect
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Posted: Tue Dec 23, 2014 6:32 am Post subject: SD8 output at 28V?

At 15:52 2014-12-22, you wrote:

 	  Quote: 	
		  



Bob,



That's really helpful information.  I currently have the 14V version 

and B&C told me that I could switch it to 28V by simply changing the 

regulator.  It sounds like that may not be the case.  (no pun intended)


	


   Hmmmm . . . I am surprised at that. I'll explore

   it further. I was involved in the SD-8 development

   wasssyyyy back when . . . in fact, that alternator

   was designed and produced at the request of Burt

   Rutan to Bill Bainbridge. Burt was alarmed at the

   heavy systems being installed on his designs and

   he was hoping that B&C could rise to the challenge

   of offering a 'tiny' system to run a few radios

   for day/vfr operations.



   The SD-8 and it's belt driven cousins were the

   outcome of Bill's response to Burt . . . and it

   put B&C on the fledgling OBAM aircraft industry's

   map.



   We worked with several combinations of wire size

   and turns on a 'stock' garden tractor alternator

   to optimize performance at pedestrian vacuum-pump

   pad speeds.  That was about 1982-84 and I've not had

   any hands-on with that system since . . . therefore

   not familiar with interim changes or the current

   design philosophy. I'll find out.

   Bob . . .

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