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Sizing a B-lead ANL

 
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Eric Page



Joined: 15 Feb 2017
Posts: 241

PostPosted: Tue Feb 22, 2022 9:35 pm    Post subject: Sizing a B-lead ANL Reply with quote

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


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user9253



Joined: 28 Mar 2008
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Location: Riley TWP Michigan

PostPosted: Wed Feb 23, 2022 8:17 am    Post subject: Re: Sizing a B-lead ANL Reply with quote

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


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Eric Page



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PostPosted: Wed Feb 23, 2022 9:03 am    Post subject: Re: Sizing a B-lead ANL Reply with quote

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

Eric


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johnbright



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PostPosted: Wed Feb 23, 2022 11:16 am    Post subject: Re: Sizing a B-lead ANL Reply with quote

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.


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PostPosted: Wed Feb 23, 2022 11:35 am    Post subject: Sizing a B-lead ANL Reply with quote

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?"


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PostPosted: Wed Feb 23, 2022 11:37 am    Post subject: Sizing a B-lead ANL Reply with quote

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?"


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Ceengland



Joined: 11 Oct 2020
Posts: 378
Location: MS

PostPosted: Wed Feb 23, 2022 1:43 pm    Post subject: Sizing a B-lead ANL Reply with quote

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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PostPosted: Wed Feb 23, 2022 7:48 pm    Post subject: Sizing a B-lead ANL Reply with quote

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?"


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Eric Page



Joined: 15 Feb 2017
Posts: 241

PostPosted: Thu Feb 24, 2022 11:49 am    Post subject: Re: Sizing a B-lead ANL Reply with quote

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?


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PostPosted: Thu Feb 24, 2022 12:56 pm    Post subject: Sizing a B-lead ANL Reply with quote

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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