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Z-13/8 Bad if both alternators on at once?

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nuckollsr(at)cox.net
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Posted: Wed Feb 15, 2006 5:22 am Post subject: Z-13/8 Bad if both alternators on at once?

At 04:01 PM 2/14/2006 -0800, you wrote:



 	  Quote: 	
		  



Would it be "bad" if the main alternator was still running and the standby

alternator were engaged?  My assumption is that which ever alternator's

regulator had the higher set point would max itself out (assuming a high

enough load) and the other alternator would pick up the rest (or idle) with

no ill effect on the system overall.  Is this true, or are there issues I'm

missing like dynamic circuit response causing some kind of feedback or the

smaller SD8 burning itself up?  A related question:  If the load is greater

than the SD-8 can support is there any consequence other than the battery

supplying the extra required current?  For instance if I flip on the battery

master and run landing lights or pitot heat or something.


	


   No, there is no risk to any system components by having both

   alternators on at the same time. The alternator having the higher

   regulation setpoint will become fully loaded before the other

   alternator . . . which is generally not a risk to the alternator

   itself. But in case of the SD-8 where the high stress component

   is the regulator, there is perhaps some risk to this device if not

   well heat-sinked.



   Generally speaking, the well designed alternator cannot be damaged

   by overloading. It simply goes into current limited operation and

   the output voltage sags. Generators from days of yore would willingly

   destroy themselves in an overload condition hence the need for BOTH

   current and voltage limiting in the generator's regulator. Alternators

   have never needed such protection.



   Bob . . .

      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

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nuckollsr(at)cox.net
Guest

Posted: Thu Feb 16, 2006 4:14 pm Post subject: Z-13/8 Bad if both alternators on at once?

At 01:52 PM 2/16/2006 -0500, you wrote:



 	  Quote: 	
		  



Scott,



Unless special provisions are made, an over voltage condition on one

alternator would trigger the over voltage protection on both.



Jon


	


    I designed the SB-1 alternator for B&C such that it

    KNOWS which of the two alternators is causing the OV

    condition. An OV condition on the main alternator will

    not trip the OV protection in the standby alternator

    when wired per Z-12.



    Bob . . .

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Jon.Goguen(at)umassmed.ed
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Posted: Fri Feb 17, 2006 3:57 pm Post subject: Z-13/8 Bad if both alternators on at once?

Bob,



Just to clarify.  Scott's original question concerned Z-13/8.  If he were to use the BC-1 regulator for his main alternator rather than the specfied generic Ford, would he avoid OV cross-talk with an SD-8 using the standard OV protection scheme?



Jon

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