Matronics Email Lists :: View topic - Low voltage indicator with dual alternators

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Low voltage indicator with dual alternators

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Jul 06, 2013 5:31 am Post subject: Low voltage indicator with dual alternators

 	  Quote: 	
		  I have the same setup and that's how it works.  That is, the low 

voltage light simply monitors the voltage on the buss independent of 

alternator operation.  Given that, I've wondered how a failed 

alternator would manifest itself.


	


     What architecture are we talking about? Z-12 or Z-14?

     With independent busses for each alternator, the two

     systems are normally operated with the cross-feed OPEN.

     Each LV montior will tell the condition of it's respective

     bus.



     With Z-12 where the aux alternator is paired with a

     Standby Regulator, the aux alternator is operated

     with the switch ON but with the lower set-point for

     the SB regulator voltage, the aux alternator normally

     'runs' in a relaxed state.



     If the main alternator is shut down for any reason,

     bus voltage sags and the SB regulator wakes up the aux

     alternator. If system loads are equal to or less than

     aux alternator capability, then the lv light will not

     come on but the AUX ALT LOADED indicator light will

     come on. If system loads are too great for the aux

     alternator, the AUX ALT LOADED light flashes to prompt

     reduction in load.



     If Z-12 with LR3C regulators, you would normally run

     with the aux alternator OFF and turn it on only when

     prompted by a LV warning . . . from either regulator

     having a warning light installed.



 	  Quote: 	
		  - If failure was due to an overvoltage situation, the breaker would 

pop.  Since I normally fly  with the 2 busses interconnected


	


     Not recommended.



 	  Quote: 	
		    I would expect the low voltage lights to remain off perhaps for 

 the remainder of the flight.  If one did come on because buss 

 voltage dropped below the threshold, I would expect both to come on 

 more or less simultaneously as long as the busses were 

 interconnected.  The only explicit indication of Alt failure would 

 be the popped OV breaker.


	


     The design goals for Z-14 were two-fold. (1)

     being able to parallel batteries for engine

     cranking and (2) being able to share power between

     systems in the event of an alternator failure.



     As you have deduced, running them in parallel

     during normal operations has the potential for

     obscuring failure of one of the alternators.



 	  Quote: 	
		  - Are there other modes of Alternator failure where there would be 

no explicit indication of failure?  I'm thinking that a snapped belt 

would be an example.  If loads and battery condition were such that 

the interconnected buss voltage stayed above the low volt threshold, 

there would be no explicit indication.  Is that right?


	


     Yes. Another reason for running them independently

     of each other for normal flight ops. With the crossfeed

     closed, you have a Z-12 with dual batteries. Unless

     one alternator is configured for stand-by operation by

     incorporation of the appropriate regulator, then you

     have two alternators in a paralleled mode of operation

     controlled by regulators not designed for paralleling

     (current management) of the two alternators.



     If you want to do this, then set the aux alternator

     regulator down by about 1 volt so that it stays 'relaxed'

     for normal ops.

   Bob . . .

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

Mauledriver(at)nc.rr.com
Guest

Posted: Mon Jul 08, 2013 8:59 am Post subject: Low voltage indicator with dual alternators

On 7/6/2013 9:31 AM, Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   

 <nuckolls.bob(at)aeroelectric.com>

> I have the same setup and that's how it works.  That is, the low 

> voltage light simply monitors the voltage on the bus independent of 

> alternator operation.  Given that, I've wondered how a failed 

> alternator would manifest itself.



     What architecture are we talking about? Z-12 or Z-14?

     With independent buses for each alternator, the two

     systems are normally operated with the cross-feed OPEN.

     Each LV montior will tell the condition of it's respective

     bus.

It's a Z-14
	


 	  Quote: 	
		  



> - If failure was due to an overvoltage situation, the breaker would 

> pop.  Since I normally fly  with the 2 buses interconnected



     Not recommended.

I see what you mean.
	


 	  Quote: 	
		  

>  I would expect the low voltage lights to remain off perhaps for the 

> remainder of the flight.  If one did come on because bus voltage 

> dropped below the threshold, I would expect both to come on more or 

> less simultaneously as long as the buses were interconnected.  The 

> only explicit indication of Alt failure would be the popped OV breaker.



     The design goals for Z-14 were two-fold. (1)

     being able to parallel batteries for engine

     cranking and (2) being able to share power between

     systems in the event of an alternator failure.



     As you have deduced, running them in parallel

     during normal operations has the potential for

     obscuring failure of one of the alternators.

My operational goals for the Z-14 included being able to run much of the 
	


panel on one battery while still having a fully charged battery for 

starting.  The idea being that I wanted to be able to enter flight plans 

and even check weather before engine start.  That's worked out well.  I 

can connect the buses for starts if needed and that works well as well.  

However, I normally start with the buses separated because if I go 

parallel, the voltage drop causes my 3 MDFs to re-boot.

 	  Quote: 	
		  

> - Are there other modes of Alternator failure where there would be no 

> explicit indication of failure? I'm thinking that a snapped belt 

> would be an example.  If loads and battery condition were such that 

> the interconnected bus voltage stayed above the low volt threshold, 

> there would be no explicit indication.  Is that right?



     Yes. Another reason for running them independently

     of each other for normal flight ops. With the crossfeed

     closed, you have a Z-12 with dual batteries. Unless

     one alternator is configured for stand-by operation by

     incorporation of the appropriate regulator, then you

     have two alternators in a paralleled mode of operation

     controlled by regulators not designed for paralleling

     (current management) of the two alternators.



I'll be going back to running independent.  I know what got me started 
	


running with the buses interconnected but I lost track of what this 

robust configuration is designed to do.



Thanks Bob!

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

Display posts from previous:

	Matronics Email Lists Forum Index -> AeroElectric-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum