Matronics Email Lists :: View topic - Definition of Alternator B-lead?

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

Definition of Alternator B-lead?

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

jgswartout(at)earthlink.n
Guest

Posted: Tue Nov 07, 2006 3:40 pm Post subject: Definition of Alternator B-lead?

Bob has recommended keeping the B-lead out of the cockpit to avoid electromagnetic interference with instruments & radios.  How much of the B-lead are we concerned about?  Looking at Z-13/8, it seems to me that all five wires connected to the battery contactor (except the master switch wire), plus the E-bus main feed path, are all electrically equivalent to the B-lead.  Does that mean, if the goal is to keep the B-lead out of the cockpit,  that the battery, the battery contactor, and the three power busses must be forward of the firewall too?  If not, where do you draw the line?  What’s the ideal, and if one must compromise, how should one prioritize component location?  

   

Thanks.  

   

John       

       [quote][b]

- 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

nuckollsr(at)cox.net
Guest

Posted: Tue Nov 07, 2006 4:45 pm Post subject: Definition of Alternator B-lead?

At 06:36 PM 11/7/2006 -0500, you wrote:



 	  Quote: 	
		  Bob has recommended keeping the B-lead out of the cockpit to avoid 

electromagnetic interference with instruments & radios.  How much of the 

B-lead are we concerned about?  Looking at Z-13/8, it seems to me that all 

five wires connected to the battery contactor (except the master switch 

wire), plus the E-bus main feed path, are all electrically equivalent to 

the B-lead.  Does that mean, if the goal is to keep the B-lead out of the 

cockpit,  that the battery, the battery contactor, and the three power 

busses must be forward of the firewall too?  If not, where do you draw the 

line?  What s the ideal, and if one must compromise, how should one 

prioritize component location?


	


   The "b-lead" is limited to that hunk of wire that

   runs from the alternator to the circuit protection

   (classically a breaker on the panel).



   The b-lead has strong magnetic fields modulated

   with alternator ripple.  It's useful to keep this

   (and all other FAT wires) as far from potential

   victims as practical . . . if everything BUT the

   bus feeders could be kept forward of the firewall,

   super. Depart from this 'ideal' as needed but make

   all practical efforts to maintain separation.



   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       >

      ---------------------------------------------------------

- 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

mprather(at)spro.net
Guest

Posted: Tue Nov 07, 2006 5:20 pm Post subject: Definition of Alternator B-lead?

I just looked at the latest z13/8 and noticed something interesting about

the drawing..  The B-lead coming from the alternator to the starter

contactor is listed as 4g.  I think that might be overkill for that

portion of the circuit, as something as small as 10g (8g to be

conservative) would do for a 60A alternator.



The output of the alternator is noisy.  Using the fatest wire to connect

the alternator to the battery provides the best filtering.  Making the

wire between the starter contactor and battery contactor perform double

duty allows using a much fatter wire for the alternator without any

penalty (for many architectures).



The RI noise will be worst on the starter end of the wire between the

starter contactor and the battery contactor.  Ideally the system

architecture would allow making the connection between the battery and

battery contactor short as compared to the connection between the battery

contactor and the starter contactor.  This will minimize the noise on the

remaining connections to the battery contactor.  Keeping the wire between

the battery contactor and the battery short also makes the contactor

perform as it's intended - to de-energize the majority of the electrical

system.



I believe there have been system architectures that routed the b-lead

directly to an ammeter on the panel, and then to the battery, with a

totally seperate wire used to power the starter.  Using a remote shunt in

line with the b-lead, as in the Z-drawing eliminates any need for such

nonsense.



If the engine is in the nose, and the battery is behind the cockpit,

obviously, the B-lead/starter_feed will go through the cockpit..  If you

have a choice, keep that wire further from the panel than you would other

wiring.  Don't use the starter end of that wire to power anything else -

make all connections as close to the battery contactor as possible.



Sorry if that seems like an indirect answer to your query...

Regards,



Matt-

 	  Quote: 	
		   Bob has recommended keeping the B-lead out of the cockpit to avoid

 electromagnetic interference with instruments & radios.  How much of the

 B-lead are we concerned about?  Looking at Z-13/8, it seems to me that all

 five wires connected to the battery contactor (except the master switch

 wire), plus the E-bus main feed path, are all electrically equivalent to

 the

 B-lead.  Does that mean, if the goal is to keep the B-lead out of the

 cockpit,  that the battery, the battery contactor, and the three power

 busses must be forward of the firewall too?  If not, where do you draw the

 line?  What's the ideal, and if one must compromise, how should one

 prioritize component location?



 Thanks.



 John

- 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

nuckollsr(at)cox.net
Guest

Posted: Wed Nov 08, 2006 5:43 am Post subject: Definition of Alternator B-lead?

At 06:18 PM 11/7/2006 -0700, you wrote:



 	  Quote: 	
		  


	


   <snip>

 	  Quote: 	
		  If the engine is in the nose, and the battery is behind the cockpit,

obviously, the B-lead/starter_feed will go through the cockpit..


	


   but easily kept low on the firewall and under the floorboards . . .



 	  Quote: 	
		     If you

have a choice, keep that wire further from the panel than you would other

wiring.  Don't use the starter end of that wire to power anything else -

make all connections as close to the battery contactor as possible.


	


    If the battery is in the rear, then the starter contactor

    becomes the forward local power distribution point for

    fat wires that connect to the alternator and main bus.



    Keeping the b-lead out of the cockpit focused very narrowly

    on the decades old practice of feeding generators/alternators

    onto the bus with panel mounted breakers.



    For fat wires in general, SEPARATION from compass for reducing

    magnetic effects is a good thing to do . . . but in small airplanes,

    it's probably impossible to get the fat wires so far from the

    compass that noticeable effects are zero. This is why compass

    swinging procedures call for making note of what electro-whizzies

    are ON during the procedure. Magnetic coupling of noise to other

    systems is easily handled by not bundling victim wires with

    fat wires.



    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