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z13/8 ess bus feed

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mmcelrea

Joined: 05 Nov 2017
Posts: 10

Posted: Sat Nov 11, 2017 3:49 pm Post subject: z13/8 ess bus feed

Hi. Building an RV7 in the UK with a G3X system and thinking of using the z13/8 architecture with the SD8 backup alt and GAD27 to maintain voltage to the GDU etc during engine start. Is it normal or acceptable to keep the essential bus alternate feed on during flight in case of battery contactor failure? I'd rather not add a second battery. I'm thinking of the scenario in case the battery contactor fails then both busses would be offline. How can power be maintained to the essential bus without a backup battery?

Thanks

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nuckolls.bob(at)aeroelect
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Posted: Sun Nov 12, 2017 4:56 pm Post subject: z13/8 ess bus feed

At 05:49 PM 11/11/2017, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "mmcelrea" <mmcelrea(at)hotmail.com>



 Hi. Building an RV7 in the UK with a G3X system and thinking of using the z13/8 architecture with the SD8 backup alt and GAD27 to maintain voltage to the GDU etc during engine start. Is it normal or acceptable to keep the essential bus alternate feed on during flight in case of battery contactor failure? I'd rather not add a second battery. 	


   Battery contactors seldom fail in fight . . . I use

   the word 'seldom' because the rate is fanishingly

   small. I've never encountered such a failure.



   A contactor on the edge of failure will raise caution

   flags by causing fussy starts or failure to close

   during start up.



   Even if it does fail, you probably wouldn't know it

   until the next preflight.



   The airplane will continue to run on the self

   excited alternator. But if you want to fly around with

   the alternate feed switch closed, it doesn't hurt

   anything but it's unnecessary.  



 

 

   Bob . . .

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mmcelrea

Joined: 05 Nov 2017
Posts: 10

Posted: Mon Nov 13, 2017 3:16 am Post subject: Re: z13/8 ess bus feed

Thankyou Bob

I am building the aircraft with approval for IFR flight here in the UK and the LAA are concerned about single failure points. Using the Z13.8 architecture is it possible to monitor if the backup alternator is working, even if its not supplying?

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nuckolls.bob(at)aeroelect
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Posted: Mon Nov 13, 2017 1:19 pm Post subject: z13/8 ess bus feed

At 05:16 AM 11/13/2017, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "mmcelrea" <mmcelrea(at)hotmail.com>



 Thankyou Bob

 I am building the aircraft with approval for IFR flight here in the UK and the LAA are concerned about single failure points. Using the Z13.8 architecture is it possible to monitor if the backup alternator is working, even if its not supplying? 	


   Not really . . . but demonstrated failure rates

   on the SD8 used in standby service is essentially

   zero. The system runs stone cold in normal flight

   meaning that thermal wear/tear on components and materials

   is zero, there are no brushes or slip rings. Further

   system is both pre-flight and in=flight testable.



   Don't know how you would get better reliability

   numbers on an engine driven power source.

    



 

 

   Bob . . .

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mmcelrea

Joined: 05 Nov 2017
Posts: 10

Posted: Wed Nov 15, 2017 12:50 am Post subject: Re: z13/8 ess bus feed

Is the SD8 on/available during normal flight? If the output is fed through a diode would that prevent the alternators 'competing' or is the voltage set at lower level than the main alternator and monitoring voltage and amps output from both alternators?

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nuckolls.bob(at)aeroelect
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Posted: Wed Nov 15, 2017 8:47 am Post subject: z13/8 ess bus feed

At 02:50 AM 11/15/2017, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "mmcelrea" <mmcelrea(at)hotmail.com>



 Is the SD8 on/available during normal flight? If the output is fed through a diode would that prevent the alternators 'competing' or is the voltage set at lower level than the main alternator and monitoring voltage and amps output from both alternators? 	


   You can run it during normal flight . . . but why?

   It's a STANDBY alternator that demonstrates exceptional

   reliability by sitting there doing NOTHING until

   pressed into service as a consequence of main

   alternator failure.



   It should be pre-flight tested . . . but allowed

   to sit in cold repose waiting for the rare failure

   of the main alternator.



 

   Bob . . .

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mmcelrea

Joined: 05 Nov 2017
Posts: 10

Posted: Fri Nov 24, 2017 12:35 pm Post subject: Re: z13/8 ess bus feed

Is it acceptable to use cb's, fuses or limiters in place of the fuse links from the stby alternator, main bus to master and the alternate essential bus feed? Also is it ok to use 1 amp fuses in place of fuse links from the shunts on a G3X system?

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nuckolls.bob(at)aeroelect
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Posted: Sat Nov 25, 2017 10:37 am Post subject: z13/8 ess bus feed

At 02:35 PM 11/24/2017, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "mmcelrea" <mmcelrea(at)hotmail.com>



 Is it acceptable to use cb's, fuses or limiters in place of the fuse links from the stby alternator, main bus to master and the alternate essential bus feed? Also is it ok to use 1 amp fuses in place of fuse links from the shunts on a G3X system?



 

 	


   Sure. Fusible links are simply a low cost, lower parts

   count, convenient substitute for the LONG TIME CONSTANT

   current limiter. Fusible links and current limiters target

   the battery-driven, hard fault condition.



   For your purposes, you can replace ANY fusible link

   shown in the drawings with a fuse or circuit breaker

   but I suggest that it only adds to cost and labor.

   But it's not 'unacceptable'.



   I would avoid using fuses lower than 3A for

   mechanical robustness concerns . . . in fact,

   for airplanes wired with nothing smaller than

   22AWG, a 5A fuse is a practical lower limit 

   for fuse selection.



 

 

   Bob . . .

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