Today's Message Index:
----------------------
1. 05:12 AM - Re: Fusible Links in lieu of ANL protectors (rockitdoc)
2. 05:48 AM - Re: Fusible Links in lieu of ANL protectors (rockitdoc)
3. 05:53 AM - Fusible Link Performance vs ANL Current Limiters (rockitdoc)
4. 08:05 AM - Re: Re: Fusible Links in lieu of ANL protectors (Robert L. Nuckolls, III)
5. 08:54 AM - Re: Fusible Link Performance vs ANL Current Limiters (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Fusible Links in lieu of ANL protectors |
nuckolls.bob(at)aeroelect wrote:
> At 05:25 PM 11/22/2022, you wrote:
>
> >
> > I am building an RV14A. I planned on using ANL current limiters for the two
alternators (60A PP and 40AB&C), but have since learned of these fusible link
thingys. I would prefer not to drill more holes in my firewall to mount the
ANLs an fusible links would foot the bill nicely. That is, if they provide
the services necessary to protect stuff.
>
> Fusible links are the way to go. Just splice them onto the
> risk-source end of your protected feeder.
>
> For the big alternator, I suggest an 8AWG (or larger)
> feeder with this fusible link.
>
> https://tinyurl.com/2md9xov3
>
> For the little alternator build a 10AWG feeder (or larger)
> with this fusible link.
>
> https://tinyurl.com/2mek723r (https://tinyurl.com/2mek723r)
>
> These are just a few options. You can buy
> BULK fusible link wire but you wind up with
> a extra wire you will probably
> never need. Buying automotive pre-fab
> links is a lot less fussy and nothing
> to inventory.
>
>
>
> Bob . . .
>
> Un impeachable logic: George Carlin asked, "If black boxes
> survive crashes, why don't they make the whole airplane
> out of that stuff?"
Thanks, Bob.
Do I need to protect the fusible link with a fire sleeve, or do the ready-made
versions come with protection? And, for that matter, does the bulk fusible link
wire come with protection?
Scott
--------
RV14A
Began 7-23-20
Fuse and tail Completed 2-20-21
Wings 99%
Finish 90%
Engine 99%
Wiring in Process
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=509082#509082
Message 2
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| Subject: | Re: Fusible Links in lieu of ANL protectors |
nuckolls.bob(at)aeroelect wrote:
> At 05:25 PM 11/22/2022, you wrote:
>
> >
> > I am building an RV14A. I planned on using ANL current limiters for the two
alternators (60A PP and 40AB&C), but have since learned of these fusible link
thingys. I would prefer not to drill more holes in my firewall to mount the
ANLs an fusible links would foot the bill nicely. That is, if they provide
the services necessary to protect stuff.
>
> Fusible links are the way to go. Just splice them onto the
> risk-source end of your protected feeder.
>
> For the big alternator, I suggest an 8AWG (or larger)
> feeder with this fusible link.
>
> https://tinyurl.com/2md9xov3
>
> For the little alternator build a 10AWG feeder (or larger)
> with this fusible link.
>
> https://tinyurl.com/2mek723r (https://tinyurl.com/2mek723r)
>
> These are just a few options. You can buy
> BULK fusible link wire but you wind up with
> a extra wire you will probably
> never need. Buying automotive pre-fab
> links is a lot less fussy and nothing
> to inventory.
>
>
>
> Bob . . .
>
> Un impeachable logic: George Carlin asked, "If black boxes
> survive crashes, why don't they make the whole airplane
> out of that stuff?"
Thanks, Bob.
Do I need to protect the fusible link with a fire sleeve, or do the ready-made
versions come with protection? And, for that matter, does the bulk fusible link
wire come with protection?
Scott
--------
RV14A
Began 7-23-20
Fuse and tail Completed 2-20-21
Wings 99%
Finish 90%
Engine 99%
Wiring in Process
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=509083#509083
Message 3
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| Subject: | Fusible Link Performance vs ANL Current Limiters |
I read a good review of this but cannot find it anywhere. Can somebody lead me
to it. The discussion regarded why the fusible link was a better method than
the ANL for electrical protection near the alternators.
--------
RV14A
Began 7-23-20
Fuse and tail Completed 2-20-21
Wings 99%
Finish 90%
Engine 99%
Wiring in Process
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=509084#509084
Message 4
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| Subject: | Re: Fusible Links in lieu of ANL protectors |
>Thanks, Bob.
>
>Do I need to protect the fusible link with a
>fire sleeve, or do the ready-made versions come
>with protection? And, for that matter, does the
>bulk fusible link wire come with protection?
>
>Scott
Check the ones in your car . . .
I wrote about his back in 2018 which I repeat here:
>Thanks so much...as usual a real education.=C2 =C2
>I had no idea that a 22 AWG fuselink is
>equivalent to a 30-40AMP fuse.=C2 =C2 Intuitively I
>thought it was much less.=C2 =C2 Much appreciated.
>
>So if a 22AWG wire is normally "rated" to 5A
>which means 10degC (Ch8-8) current rise
>presumably therefore needs 40A to get to melting point.=C2
Exactly . . . see https://goo.gl/zye61w
Circuit protection is about keeping insulation
temperatures comfortably below maximum rated
operating vales. Wire size is all about maintaining
distribution voltage drops below acceptable levels
based on system design goals. 5% is the max-drop
rule of thumb although other values may be adopted
by program managers.
Wire sizing tends to be very conservative . . . unless
you are as weight-sensitive as a moon mission or
Voyager flight, the design rules will keep wires
pretty cool.
>By the same token the 16AWG fuselink at the
>starter contactor (from the alternator) and from
>the battery contactor to the buss performs in a
>similar way. If this is correct the 16AWG
>fuselink rated at 12.5A for 10 degC current rise
>will melt at something like 100A. Whereas the
>12AWG wire it's protecting will melt at something like 150.
Fusible links in vehicles are expected to protect
major feeders of a distribution system against
hard faults . . . generally experienced only during
major disassembly of the vehicle. By hard fault,
were talking many times hundreds to thousands of
amps supplied by a battery . . . not the soft
fault precipitated by a failing appliance.
https://goo.gl/QEBeZs
>Is this correct?
Generally . . . When we use plain-vanilla wire
as a fusible link in the OBAM aircraft world, it's
a good idea to use the silicone/fiberglas sleeving
over it to limit the propagation of heat damage
during a fusing event. In the ground transportation
industries, fusible links are fabricated from wire
having friendlier outcomes during the fusing event.
Hypalon insulation (A Dupont product that targeted
electric locomotives in mines) is used on many
fusible link replacement assemblies available at your
local car parts stores . . . or in bulk wire on
places like eBay.
https://goo.gl/RH2eEY
The material selected for a fusible link has
little to do the loads presented by downstream
appliances. The wire in fusible link is EXPECTED
to burn . . . at many degrees above the insulation
rating. Selection of material is about reduction
of risk in the rare but catastrophic event.
So, fusible link wire is simply used as a short extension
of the feeder to be protected by splicing a short chunk
(6-10 inches) onto the end of the feeder.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 5
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| Subject: | Re: Fusible Link Performance vs ANL Current Limiters |
At 07:52 AM 11/23/2022, you wrote:
><scott.shuler@colostate.edu>
>
>I read a good review of this but cannot find it anywhere. Can
>somebody lead me to it. The discussion regarded why the fusible
>link was a better method than the ANL for electrical protection near
>the alternators.
'Better' is not a very quantifiable term when applied
out of context. The design goal calls for reduction of
risk to certain conductors in the system against hazardous
fault currents. How much current? In this case, a battery
feed fault with a potential for hundreds of amps
for an extended period of time. Precipitating event?
Destruction of semiconductor devices in (1) output of
alternator or (2) rectifier regulator.
Options? Fuses, circuit breakers, current limiters, fusible
link, etc.
With respect to functionality, ANY of these would serve
just fine. Design goals? Hmmmm . . . ease of installation,
reduction of weight, minimum cost, attractive service life,
or any combination of these.
Fuses, current limiters, breakers have significant costs
for procurement and installation. They may also feature
threaded fasteners which adds to complexity and risk of
loss of integrity due to environmental effects or deficiencies
in craftsmanship.
The lightest and lowest parts count approach is the fusible
link. Tooling and skills are no greater than required
for all other wires and terminals in the system. So unless
constrained by other design goals favoring alternatives,
I suggest that fusible links are the elegant solution to
a VERY LOW RISK problem.
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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