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Z13/8, max. E-bus and self-excitation

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Camillo

Joined: 09 May 2008
Posts: 2

Posted: Fri May 09, 2008 5:35 am Post subject: Z13/8, max. E-bus and self-excitation

Hi. I read all the book, surfed the forum and still have a couple of questions regarding to the Z13/8 architecture I want to use for my RV9A.

1) Is there any reason why I cannot put almost every load on E-bus and then switch what's not necessary off via breakers? I mean, if battery contactor fails, I could not use all loads on main bus. If main alternator/battery contactor fails, I can select what I need to remain under 8/10 amp. (maybe I didn't understand the book, but if I use only CB and not fuses [so I can place everything on the E-bus and switch unnecessary off], would be OK to leave only "start" circuit [and switch] on the main bus? Is the high current for a start the main reason for placing the main bus after the "battery relay" and not per the E-bus way [being controlled by a switch and not by a relay?)

2) Is Z25 self excitation mode utility needed in case of a battery short?

Edit: I found a post in which Bob said it is only needed in a cold start without a battery OR, as I can understand, if alternator will be "stalled" (under an overload). Is it right?



Thank-you.

Camillo

RV9A

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nuckolls.bob(at)cox.net
Guest

Posted: Fri May 09, 2008 7:26 am Post subject: Z13/8, max. E-bus and self-excitation

At 06:35 AM 5/9/2008 -0700, you wrote:



 	  Quote: 	
		  



Hi. I read all the book, surfed the forum and still have a couple of 

questions.



1) Is there any reason why I cannot put almost every load on E-bus and 

then switch what's not necessary off via breakers? I mean, if battery 

contactor fails, I could not use all loads on main bus. If main 

alternator/battery contactor fails, I can select what I need to remain 

under 8/10 amp.


	


   Sure . . . you can do that. Why would you want to?

   The point of the e-bus is to maximize utilization of a

   limited resource of energy (battery) during alternator

   out operations with a minimum of pilot work load (minimum

   risk of doing something undesirable under stressful

   conditions) and dual feedpaths for power.



   Obviously, there are countless combinations of architecture,

   bus loading and "plans-b" one could craft for their

   project. All combinations would function as designed.

   The questions to be asked and answered is what

   benefits are derived by departing from a repeatable

   experiment where design goals have been debated and

   refined for over a decade?



   In other words, what shortcoming do you perceive in Z13/8

   as published. What design goals do you have that are not

   addressed by Z13/8? Perhaps Z12 is a better fit for

   you.

 	  Quote: 	
		  2) Is Z25 self excitation mode utility needed in case of a battery short?


	


   No, in case the battery is not available . . . I.e. disconnected.

        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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Camillo

Joined: 09 May 2008
Posts: 2

Posted: Fri May 09, 2008 9:48 am Post subject: Re: Z13/8, max. E-bus and self-excitation

 	  Quote: 	
		  Sure . . . you can do that. Why would you want to?

   The point of the e-bus is to maximize utilization of a

   limited resource of energy (battery) during alternator

   out operations with a minimum of pilot work load (minimum

   risk of doing something undesirable under stressful

   conditions) and dual feedpaths for power. 	




Among the others instruments, I'm planning a Dynon D10A, a GPS and an ADI, all with internal batteries and I would like to disconnect them from airplane power to lower aux. alternator load in case of primary alternator failure. But, I still would be able to use plane power for them, if necessary. I understand the pilot work stress came from switching each one off separately, but I plan to mark the three said breakers in yellow in the CB panel and to make a remind above the main alt. warning light (i.e.: in case of failure, switch off bks. x,y,z). In addition, I'm planning to do IFR and I would not like to have NAV/COMM off (for a mayday or a radar assistance to home). So, if I have to keep at least this things on the E-bus, I thought it would be better to have all on it.



   	  Quote: 	
		  Obviously, there are countless combinations of architecture,

   bus loading and "plans-b" one could craft for their

   project. All combinations would function as designed.

   The questions to be asked and answered is what

   benefits are derived by departing from a repeatable

   experiment where design goals have been debated and

   refined for over a decade?

  In other words, what shortcoming do you perceive in Z13/8

   as published. What design goals do you have that are not

   addressed by Z13/8? Perhaps Z12 is a better fit for

   you. 	




I chose Z13/8 because I understood that in Z12 SD-20 would not work without a battery and adding a second battery would have not been a great idea, since an RV9 is not a Boeing (actually, the idea was to pass to Z-14, since the step would have been short...the Boeing relates to this). So, I thaught SD8, even if less powerful, would have been a better choice in terms of safety (cost and weight). Also, I can't say if Z12 could be adapted to receive SD-8. If yes, I anyway doubt it would be good choice: the battery contactor will take 1 amp. off!. In such event, will it work with SB-1 (great capability having it...) or shall it be activated manually as per Z13/8?



At the end of this, I may guess options are:

- Z13/8 as I said;

- Z12 (L40 + SD20) with Z35 to supply power to secondary alternator.



 	  Quote: 	
		  No, in case the battery is not available . . . I.e. disconnected. 	




Sorry...I may need a fourth reading of the book here. If battery is shorted I would have no alternative than using analogic instrument and internally powered electronics one. Isn't it?



Thank-you again.

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mprather(at)spro.net
Guest

Posted: Fri May 09, 2008 11:25 am Post subject: Z13/8, max. E-bus and self-excitation

 	  Quote: 	
		   

 <ungaritrasatti(at)alice.it>


	


snip

 	  Quote: 	
		   Among the others instruments, I'm planning a Dynon D10A, a GPS and an ADI,

 all with internal batteries and I would like to disconnect them from

 airplane power to lower aux. alternator load in case of primary alternator

 failure. But, I still would be able to use plane power for them, if

 necessary.


	


I wonder how much power these items will draw when the main bus voltage

drops after an alternator failure.  It might be slick if they'd switch to

internal battery if the bus voltage drops down to ~12V..  Not terribly

difficult to accomplish.

Regards,



Matt-

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