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Sizing a B-lead ANL

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Eric Page

Joined: 15 Feb 2017
Posts: 245

Posted: Tue Feb 22, 2022 9:35 pm Post subject: Sizing a B-lead ANL

I'm asking for a friend, who is installing a Verner radial engine on a Kitfox...



In some of the Z-figures, ANL current limiters are annotated as "sized to alternator."  In others, the annotation refers to Note 10, which doesn't discuss sizing.  On Z-12, the alternator is labeled as 60A, and the ANL is annotated as "ANL60."



So, should the ANL rating match the alternator nameplate rating as closely as possible, or slightly exceed it, or is there some other formula?  I didn't find anything specific in the text of the 'Connection, and a search on the forum came up empty as well.



Thanks,



Eric

user9253

Joined: 28 Mar 2008
Posts: 1925
Location: Riley TWP Michigan

Posted: Wed Feb 23, 2022 8:17 am Post subject: Re: Sizing a B-lead ANL

https://www.eaton.com/content/dam/eaton/products/electrical-circuit-protection/fuses/data-sheets/bus-ele-ds-2024-anl.pdf

The rating of the ANL current limiter should NOT exceed the alternator rating.

Alternators are self current limiting.  The purpose of the fuse is to protect the battery and electrical system from "B" lead and alternator short circuits.

The rating of the fuse should be chosen so that it will never blow while conducting maximum alternator current output.

Your friend might consider a maxi fuse.  They look like giant ATC fuses.

https://m.littelfuse.com/~/media/automotive/datasheets/fuses/passenger-car-and-commercial-vehicle/blade-fuses/littelfuse_maxi_58v_datasheet.pdf

_________________
Joe Gores

Eric Page

Joined: 15 Feb 2017
Posts: 245

Posted: Wed Feb 23, 2022 9:03 am Post subject: Re: Sizing a B-lead ANL

Thanks very much, Joe.  I'll pass that along.



Eric

johnbright

Joined: 14 Dec 2011
Posts: 165
Location: Newport News, VA

Posted: Wed Feb 23, 2022 11:16 am Post subject: Re: Sizing a B-lead ANL

I haven't been able to find a definition or history of current limiters, but, at least in the case of ANL current limiters of the ratings we use, it seems like they are designed so you don't have to calculate how much bigger than the load to size them, just use one placarded for your load. Note a 60A ANL will carry over 100A continuously. 



Here's what I put on my schematic:



Littlefuse MIDI/Bussmann AMI fuses are specified on this schematic for the alternator B leads versus legacy ANL current limiters because they are physically smaller.



ANL current limiters with the same rating as the alternator could be used but MIDI fuses of a higher rating are chosen. It is assumed the alternator is capable of 120% of its rated output, this is divided first by 0.75 (nuisance blowing factor per Littelfuse "Fuseology" document) and then by 0.95 (temperature re-rating factor per Littelfuse MIDI data sheet, 170F firewall temperature is assumed).



Main alternator: (60 * 1.2) / (0.75 * 0.95) = 101 A, close enough to 100 to choose a 100 A MIDI.

  

Vacuum pad alternator: (35 * 1.2) / (0.75 * 0.95) = 59 A, a 60 A MIDI is chosen.



Alternate for alternator B leads is FLW (fuse link wire) 6" long, 4 awg smaller than B lead, PICO brand is common; available from 10 to 20 awg. FLW is a slightly cleaner installation; ANLs, and especially MIDIs, open with less energy.

_________________
John Bright, RV-6A, at FWF, O-360
Z-101 single batt dual alt SDS EM-5-F.
john_s_bright@yahoo.com, Newport News, Va
N1921R links

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Feb 23, 2022 11:35 am Post subject: Sizing a B-lead ANL

At 11:35 PM 2/22/2022, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "Eric Page" <edpav8r(at)yahoo.com>



 I'm asking for a friend, who is installing a Verner radial engine on a Kitfox...



 In some of the Z-figures, ANL current limiters are annotated as "sized to alternator."  In others, the annotation refers to Note 10, which doesn't discuss sizing.  On Z-12, the alternator is labeled as 60A, and the ANL is annotated as "ANL60."



 So, should the ANL rating match the alternator nameplate rating as closely as possible, or slightly exceed it, or is there some other formula?  I didn't find anything specific in the text of the 'Connection, and a search on the forum came up empty as well.

 	


   ANL devices are EXCEEDINGLY robust



  http://aeroelectric.com/Mfgr_Data/Fuses_and_Current_Limiters/Bussman/ANL_Specs.pdf 



   An ANL60 will carry over 100A continuously.

   This tells us that current limiters are designed

   to mitigate HARD faults (many hundreds of Amps).

   So picking an ANL equal to or even SMALLER than

   the alternator is not a sketchy idea.



   Alternatively, consider a fusible link (4AWG

   smaller than B-lead). This will serve the same

   purpose and is often less expensive and more

   installer-friendly.



   As the Z-figures evolve, ANL and similar

   devices are going to be replaced with fusible

   links.



 

 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Feb 23, 2022 11:37 am Post subject: Sizing a B-lead ANL

At 01:16 PM 2/23/2022, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "johnbright" <john_s_bright(at)yahoo.com>



 I haven't been able to find a definition or history of current limiters, but, at least in the case of ANL current limiters of the ratings we use, it seems like they are designed so you don't have to calculate how much bigger than the load to size them, just use one placarded for your load. Note a 60A ANL will carry over 100A continuously. 



 Here's what I put on my schematic:



 Littlefuse MIDI/Bussmann AMI fuses are specified on this schematic for the alternator B leads versus legacy ANL current limiters because they are physically smaller.



 ANL current limiters with the same rating as the alternator could be used but MIDI fuses of a higher rating are chosen. It is assumed the alternator is capable of 120% of its rated output, this is divided first by 0.75 (nuisance blowing factor per Littelfuse "Fuseology" document) and then by 0.95 (temperature re-rating factor per Littelfuse MIDI data sheet, 170F firewall temperature is assumed).



 Main alternator: (60 * 1.2) / (0.75 * 0.95) = 101 A, close enough to 100 to choose a 100 A MIDI.

   

 Vacuum pad alternator: (35 * 1.2) / (0.75 * 0.95) = 59 A, a 60 A MIDI is chosen.



 Alternate for alternator B leads is FLW (fuse link wire) 6" long, 4 awg smaller than B lead, PICO brand is common; available from 10 to 20 awg. FLW is a slightly cleaner installation; ANLs, and especially MIDIs, open with less energy. 	


   Exactly. But life is much simpler with fusible links.



 

 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

Ceengland

Joined: 11 Oct 2020
Posts: 391
Location: MS

Posted: Wed Feb 23, 2022 1:43 pm Post subject: Sizing a B-lead ANL

snipped

      	  Quote: 	
		  

           Alternatively, consider a fusible link (4AWG

           smaller than B-lead). This will serve the same

           purpose and is often less expensive and more

           installer-friendly.

         

           As the Z-figures evolve, ANL and similar

           devices are going to be replaced with fusible

           links.

         

         

                

             Bob . . .

            	
     That's what I did. I confess to using a pair of off-the-shelf Denso     internally regulated alternators, with the OV protection on a pair     of continuous duty contactors on the firewall. The blue wires in the     pic are actually 12awg fusible link wire, doing double duty as     interconnects and protection for the 8awg B leads (~2 foot runs). 

     

     Needless to say, I'm a big fan of using links.

     

     Charlie

     	          		Virus-free. www.avast.com 		 	 [url=#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2] [/url]

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_________________
Charlie

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Feb 23, 2022 7:48 pm Post subject: Sizing a B-lead ANL

 	  Quote: 	
		  That's what I did. I confess to using a pair of off-the-shelf Denso internally regulated alternators, with the OV protection on a pair of continuous duty contactors on the firewall. The blue wires in the pic are actually 12awg fusible link wire, doing double duty as interconnects and protection for the 8awg B leads (~2 foot runs). 



 Needless to say, I'm a big fan of using links. 	


   me too . . .



 

   The probability of a hard-fault to a b-lead is exceedingly

   low . . . but FMEA protocols do not consider 'exceedingly

   low' . . . they ASSUME that if a failure is at all possible, then

   design mitigation into the system.



   This is how mission-reliability is promoted . . . mission

   critical features of the airplane are first rendered

   non-hazardous and then backed up by a system unlikely

   to be affect by the same stresses while you finish consuming

   one tank full of fuel. Hence, NO SYSTEM is really mission-

   critical irrespective of the MTBF numbers.



   ANL and similar devices are parts, installation and cost

   intensive while adding an incalculably small if not

   zero value to system reliability. So a piece of 'magic

   wire' with a terminal on one end and splice on the other

   seems quite practical.



 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

Eric Page

Joined: 15 Feb 2017
Posts: 245

Posted: Thu Feb 24, 2022 11:49 am Post subject: Re: Sizing a B-lead ANL

Thanks, everyone.  I've given my friend a link to this thread so he can absorb the hive's wisdom directly.



One other question he asked me is whether or not to carry a spare for whatever B-lead protection he chooses, whether it's ANL, Maxi or fusible link.  Thoughts, pro or con?

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Feb 24, 2022 12:56 pm Post subject: Sizing a B-lead ANL

At 01:49 PM 2/24/2022, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "Eric Page" <edpav8r(at)yahoo.com>



 Thanks, everyone.  I've given my friend a link to this thread so he can absorb the hive's wisdom directly.



 One other question he asked me is whether or not to carry a spare for whatever B-lead protection he chooses, whether it's ANL, Maxi or fusible link.  Thoughts, pro or con? 	


  If you've popped a b-lead protector . . . having a spare

  is the least of your worries. If this protection ever

  opens, there's a SERIOUS issue to be addressed.



  In fact, if he is using fuseblocks as opposed to

  breakers, council him on temptations to fiddle

  with ANY fuse or breaker in flight. . .



  See:  http://aeroelectric.com/articles/fusvsbkr.html



 

 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

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