Today's Message Index:
----------------------
1. 05:34 AM - Re: Re: Fusible links vs fuses (James Kilford)
2. 05:59 AM - Alternator protection ANL-40 rating (James Kilford)
3. 06:51 AM - Re: Alternator protection ANL-40 rating (Robert L. Nuckolls, III)
4. 06:54 AM - Re: Re: Fusible links vs fuses (Robert L. Nuckolls, III)
5. 07:01 AM - ANL-40 mounting (James Kilford)
6. 07:27 AM - Re: Fusible links vs fuses (rckol)
7. 07:34 AM - Re: Re: Fusible links vs fuses (James Kilford)
8. 09:24 AM - Re: Re: Fusible links vs fuses (Robert L. Nuckolls, III)
9. 12:17 PM - Re: Re: Fusible links vs fuses (Robert L. Nuckolls, III)
10. 02:41 PM - Re: Radio mounting (Jae Chang)
Message 1
INDEX | Back to Main INDEX |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Fusible links vs fuses |
Thanks for that rck.
So the fusible link is just intended to be a worst-case-scenario,
probably-won't-ever-blow fuse. Makes sense as it reduces joints.
What Bob wrote about the alternator is interesting, and makes me think
of another question, which I'll post separately.
James
On Fri, Apr 2, 2010 at 9:55 PM, rckol <rckol@kaehlers.com> wrote:
>
> James,
>
> The fuseable link is to protect the wire between the bus and the breaker. The
breaker is there as part of the overvoltage protection circuit. If you get an
overvoltage event, you want the resetable breaker to trip, not the proposed fuse
to blow, hence the sturdier fuseable link.
>
> --------
> rck
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=292811#292811
>
>
Message 2
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Alternator protection ANL-40 rating |
Bob,
Interesting what you said about the B-lead protection.
I had thought that my (planned) ANL-40 is going to protect the B-lead
wire from the battery. It's interesting to read about this
over-current scenario that could end up blowing the ANL-40 in a
"normal" situation, i.e. something designed to protect has introduced
a new failure mode.
However, I read on the B&C Specialty web site that the ANL-40 can
handle 80% more current than its rated capacity on a continuous basis.
It sounds as though this is going to stand anything extra the
alternator can put out. Is this assertion correct?
Thanks in anticipation,
James
On Sat, Apr 3, 2010 at 5:07 AM, Robert L. Nuckolls, III
<nuckolls.bob@aeroelectric.com> wrote:
> <nuckolls.bob@aeroelectric.com>
>
> At 10:14 PM 4/2/2010, you wrote:
>>
>>
>> James,
>>
>> The 5 amp breaker in the line controlling the regulator is for overvoltage
>> protection, assuming you are using a B&C or PlanePower regulator for an
>> externally regulated alternator or are using a PlanePower internally
>> regulated alternator with built in OV protection (or an OVM-14 module).
>>
>> Your overcurrent protection would be in the form of a big breaker or fuse
>> (40+ amps) on the B lead (output) of the alternator.
>
> Very close except that alternators don't require over-current
> protection like their older cousins, the generator.
>
> Alternators are magnetically limited in their ability
> to deliver current . . . so as the load on an alternator
> goes up, there comes a time about 10-20% over nameplate
> rating where the critter wont deliver any more and the
> output sags.
>
> Maximum output from the alternator happens when the
> machine is cold. On rare occasions (cold morning,
> jump start dead battery, battery is relatively
> new and will accept lots of recharge current)
> one can get a nuisance trip of the 60A breaker
> in an airplane fitted with a 60A alternator.
> This is because total ship's electrical loads
> plus battery recharge current will be what ever
> the alternator will deliver . . . which may be
> greater than the 60A breaker rating on the
> panel.
>
> This happened to me once . . . the second of
> only two times I've had a breaker open in flight.
> This is why we select b-lead protection well above the
> name-plate rating for the alternator so that the
> breaker doesn't nuisance trip. It's also why I
> call the 60A breaker on most Cessnas and Pipers
> the "breaker designed to nuisance trip".
>
> In any case, the b-lead breaker is to protect
> the rest of the system if you get shorted diodes
> in the alternator (very rare). The fusible link
> in most cares serves the same purpose.
>
> Bob . . .
>
>
Message 3
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Alternator protection ANL-40 rating |
At 07:55 AM 4/4/2010, you wrote:
>
>Bob,
>
>Interesting what you said about the B-lead protection.
>
>I had thought that my (planned) ANL-40 is going to protect the B-lead
>wire from the battery. It's interesting to read about this
>over-current scenario that could end up blowing the ANL-40 in a
>"normal" situation, i.e. something designed to protect has introduced
>a new failure mode.
>
>However, I read on the B&C Specialty web site that the ANL-40 can
>handle 80% more current than its rated capacity on a continuous basis.
> It sounds as though this is going to stand anything extra the
>alternator can put out. Is this assertion correct?
Correct. One COULD use a fuse or breaker in the b-lead.
They just need to be sized such that the alternator would
NEVER open the breaker even when temporarily "overloaded".
ANL limiters use the same schematic symbol as a fuse
because they ARE a very robust, one-time, melting element
protector, i.e. "fuse". But the differences in response
time for the ANL limiter and the ATC fuse are huge. Circuit
breakers fall in between.
A fundamental of power distribution system architecture
is to install over-current protection devices (1) to
prevent a wire from becoming overheated to the point
of becoming hazardous and (2) isolate the faulted branch
of the system without propagating the failure to other
branches.
This means that as you move from the load to the
source of power, the circuit protective devices must
become increasingly robust as you move toward the
source. This idea is common to all reliable, failure
tolerant power distribution systems. For example:
A fuse inside a toaster is much less robust (faster
acting) than the breaker in a home's power distribution
box. The breaker in the box is much less robust than
the protection for a transformer on the pole which
powers multiple houses. As one moves upstream toward
the power source, the relative robustness of each
protective device must be sized to allow operation
of any single protective device in the system without
tripping any protection upstream. This prevents a
short in a toaster from turning out lights in the
whole neighborhood.
A design goal for the crowbar ov protection system
is to place the responding circuit breaker in reach
of the pilot. IF your airplane is fitted with legacy
panel mounted bus-bars and acres-of-breakers, then
integration of the crowbar-ov protection system is
no big deal. If you're using remotely mounted fuse
blocks, then there's got to be a piece of wire that
runs from the bus (fuse block feed terminal) to the
circuit breaker on the panel. Legacy design practice
and common sense tells us to protect that wire with
some device that is more robust than the breaker,
hence the fusible link . . . which is a little
brother to an ANL limiter.
Compare the operating characteristics of the
ATC plastic fuse with ANL limiters . . .
http://aeroelectric.com/Mfgr_Data/Fuses_and_Current_Limiters/Bussman/ATC_Specs.pdf
http://aeroelectric.com/Mfgr_Data/Fuses_and_Current_Limiters/Bussman/ANL_Specs.pdf
and a typical miniature aircraft circuit breaker.
http://aeroelectric.com/Mfgr_Data/Breakers/Eaton/Eaton_4200.pdf
Under mild overload (2x rating) a fuse will be expected
to operate in about 50-100 mS, the breaker in 1-2 seconds
and an ANL never.
These differences in robustness suggest their proper
position in a power distribution system where they might
be in series with each other. Getting them out of
order can produce some unhappy results in a system that
is not failure tolerant.
Bob . . .
Message 4
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Fusible links vs fuses |
At 07:31 AM 4/4/2010, you wrote:
>
>Thanks for that rck.
>
>So the fusible link is just intended to be a worst-case-scenario,
>probably-won't-ever-blow fuse.
Correct.
> Makes sense as it reduces joints.
That was the goal. Automobiles have
See:
http://www.aeroelectric.com/articles/fuselink/fuselink.html
There's a lot of discussion on the whys and wherefors
for fusible links in the FAQ
http://www.aeroelectric.com/FAQ/AeroElectric-List/AeroElectric-List_FAQ.pdf
Do a search on "fusible" to get a good review
of their development, application and incorporation
into AEC Z-figures.
Bob . . .
Message 5
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Gents,
I forgot to ask when on the subject of ANL-40s, if there is a slightly
less "industrial" way of mounting an ANL-40. The holder I have for it
looks as though it's from an electricl sub-station, and weighs about
50lbs (a slight exaggeration perhaps).
Is it poor practice to mount the ANL-40 in some other way, perhaps
in-line to the B-lead close to the starter contactor?
Thanks in anticipation,
James
Message 6
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Fusible links vs fuses |
Bob,
Am I correct in thinking that in the rare "shorted alternator diode" scenario,
the alternator is providing a low resistance path to ground and the power source
that the big breaker or fuse is interrupting is in fact the battery?
--------
rck
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=292940#292940
Message 7
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Fusible links vs fuses |
Bob,
The FAQ is an awesome body of knowledge! I started reading it from
top to bottom... about 20 pages in I noticed it's 310 pages! After
that, Control-F became my friend!
I can't remember how I stumbled across your Aeroelectric Connection
book, and this list, but I'm extremely glad I did. It's funny how we
spend all this time and money building our planes, knowing every part
and rationalising every decision... until we get to the electrics...
then we just do exactly what Cessna and Piper have done forever,
because "it must be fine".
It's great to have done an electrical system the AC way: to plan
properly, to question it all in the same way, and learn about why
something is or isn't appropriate. It's also good to be able to
answer people's questions ("why don't you have breakers?" or "why
can't you change your fuses in flight?", etc) from a position of
knowing that, even if something turns out not to be perfect, at least
it was thought about in the first place.
James
On Sun, Apr 4, 2010 at 2:54 PM, Robert L. Nuckolls, III
<nuckolls.bob@aeroelectric.com> wrote:
> <nuckolls.bob@aeroelectric.com>
>
> At 07:31 AM 4/4/2010, you wrote:
>>
>>
>> Thanks for that rck.
>>
>> So the fusible link is just intended to be a worst-case-scenario,
>> probably-won't-ever-blow fuse.
>
> Correct.
>
>> Makes sense as it reduces joints.
>
> That was the goal. Automobiles have
>
> See:
>
> http://www.aeroelectric.com/articles/fuselink/fuselink.html
>
> There's a lot of discussion on the whys and wherefors
> for fusible links in the FAQ
>
> http://www.aeroelectric.com/FAQ/AeroElectric-List/AeroElectric-List_FAQ.pdf
>
> Do a search on "fusible" to get a good review
> of their development, application and incorporation
> into AEC Z-figures.
>
> Bob . . .
>
>
Message 8
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Fusible links vs fuses |
>Am I correct in thinking that in the rare "shorted alternator diode"
>scenario, the alternator is providing a low resistance path to
>ground and the power source that the big breaker or fuse is
>interrupting is in fact the battery?
Absolutely. Compared to the alternator, the battery
is the single most "dangerous" in terms of energy
dumped during a fault . . . a new 35 a.h. RG battery
can source over 2000 amps when presented with a short.
So yes, the b-lead protection is not going to be
tripped by the alternator but the battery when
some (very rare) failure in the alternator presents
the short.
I've seen alternator stator leads burn before the
ANL in the b-lead burned. So it may be that most
alternators are pretty well "self limiting" in
terms of effects on the rest of the system during
and right after a fault. But without extensive
testing/analysis, I wouldn't want to bet on it.
I forgot to ask when on the subject of ANL-40s, if there is a slightly
less "industrial" way of mounting an ANL-40. The holder I have for it
looks as though it's from an electricl sub-station, and weighs about
50lbs (a slight exaggeration perhaps).
They are pretty beastly . . . consider the miniature
automotive equivalents to the ANL. Or, if you're
doing b-lead protection on a 40A alternator, how about
a 60A maxi-fuse. The ANL is not the be-all-end-all
solution to the design goal.
You can build your own holder for a mini-anl out
of phenolic, delrin or other robust insulator material.
This was discussed a few days ago here on the List.
Is it poor practice to mount the ANL-40 in some other way, perhaps
in-line to the B-lead close to the starter contactor?
The goal is to place circuit protection as close
as possible to the SOURCE of the energy likely to
open the fuse. Note in all the Z-figures (at least
I think I got it done on all of them) the wire on
the battery side of the b-lead protection is marked
with a (*). That symbol on the drawing suggests
"make this wire as short as practical".
Bob . . .
Message 9
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Fusible links vs fuses |
At 09:33 AM 4/4/2010, you wrote:
>
>Bob,
>
>The FAQ is an awesome body of knowledge! I started reading it from
>top to bottom... about 20 pages in I noticed it's 310 pages! After
>that, Control-F became my friend!
Yeah, a reader on the List compiled that document some
years ago . . . it needs updating and editing. But
as you've discovered, the "find function" is very useful
for sifting all the sand.
>I can't remember how I stumbled across your Aeroelectric Connection
>book, and this list, but I'm extremely glad I did. It's funny how we
>spend all this time and money building our planes, knowing every part
>and rationalising every decision... until we get to the electrics...
>then we just do exactly what Cessna and Piper have done forever,
>because "it must be fine".
And that's not wrong . . . but it does carve your airplane's
electrical system into "legacy stone". Probably 90% of all
OBAM aircraft are wired like Uncle's Walter, Duane, and
Bill have been doing it for 60+ years and it works as
advertised.
>It's great to have done an electrical system the AC way: to plan
>properly, to question it all in the same way, and learn about why
>something is or isn't appropriate. It's also good to be able to
>answer people's questions ("why don't you have breakers?" or "why
>can't you change your fuses in flight?", etc) from a position of
>knowing that, even if something turns out not to be perfect, at least
>it was thought about in the first place.
Exactly! It would not yank my chain in the least if EVERYBODY
wired their airplanes like a C-150 if I thought they understood
how all the parts worked and made their decision from
informed choice based not upon tradition or authoritative
suggestion but from understanding.
Thank you for the kind words. I'm pleased that you
find the work informative and useful.
Bob . . .
Message 10
INDEX | Back to Main INDEX |
PREVIOUS | Skip to PREVIOUS Message |
NEXT | Skip to NEXT Message |
LIST | Reply to LIST Regarding this Message |
SENDER | Reply to SENDER Regarding this Message |
|
Subject: | Re: Radio mounting |
http://lh4.ggpht.com/_E3nI7J8M6Iw/S51_ptBMY7I/AAAAAAAAAsI/GKgzSIQV4jk/s800/IMG_0180.JPG
I discovered this very same thing between an GTX-327, SL-30, and
GMA-240. I was surprised when the Al strips I was using to mock things
up bent wide. It turns out the transponder and audio panel are about the
same width. The SL-30 was narrower. Go figure. I ended up adding some
thin washers (AN960-6L, i think) washers as shims for the SL-30.
http://lh5.ggpht.com/_E3nI7J8M6Iw/S7FQD00QWnI/AAAAAAAAA00/5M3r8fpRx3E/s800/IMG_0195.JPG
http://lh3.ggpht.com/_E3nI7J8M6Iw/S6uYQIP_1LI/AAAAAAAAAzM/4wXobq_U904/s800/IMG_0192.JPG
The above are some pictures of how I mounted my 3 items. All this is
completely new to me, so I have no idea if this is right or wrong. Also,
in my setup, to get the flush fit I wanted, the racks extend into my
panel cutout a bit. The install manuals have plenty of warnings about
making sure the connectors get seated properly.
Jae
RV-10
Bill Schlatterer wrote:
> Pix worth a thousand :-) This is a 430W tray and a SL40 Tray from Garmin.
> Definitely not the same size but I think I remember the SL40 is slightly
> smaller than the 430 as I had to add shims and the 430w tray was 6.25. 6.38
> would have been a little better as mine is snub. Note that Garmin didn't
> design the SL40 and SL30, those came with the Apollo acquisition as I
> remember which probably accounts for the difference in tray sizes.
>
> Bill S
> 7a just weeks away :-)
>
>
>
>
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|