Today's Message Index:
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1. 04:11 AM - Fusable link (JOHN TIPTON)
2. 04:13 AM - Re: Fusable link (JOHN TIPTON)
3. 05:40 AM - Re: Fusable link (Robert L. Nuckolls, III)
4. 05:58 AM - FYI - LMR195 coax (Robert L. Nuckolls, III)
5. 11:22 AM - Re: Fusable link (JOHN TIPTON)
6. 05:36 PM - Re: Re: Fusable link (Robert L. Nuckolls, III)
7. 08:17 PM - Re: Re: Fusable link (Jeff Luckey)
Message 1
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Hi Guys (Bob)
I see that Z11 is using a fuse block as opposed the CBs (no problem there), can
you tell me why the feed to the 5a CB has a fuse able link, why not use a fuse
in the distribution fuse block
Best regards
John
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=422991#422991
Message 2
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| Subject: | Re: Fusable link |
Ps: the 5amp CB did relate to the alternator feed circuit
John
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=422992#422992
Message 3
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| Subject: | Re: Fusable link |
At 06:09 AM 5/8/2014, you wrote:
<jmtipton@btopenworld.com>
Hi Guys (Bob)
I see that Z11 is using a fuse block as opposed the CBs (no problem
there), can you tell me why the feed to the 5a CB has a fuse able
link, why not use a fuse in the distribution fuse block
Best regards
John
The length of wire from fuse block feeder terminal
out to the circuit breaker is an EXTENSION of the
bus. In larger aircraft the bus feeders will sometimes
be protected by a VERY robust fusible device like
the ANN/ANL series of "current limiters" . . .
http://aeroelectric.com/Mfgr_Data/Fuses_and_Current_Limiters/Bu
http://tinyurl.com/lrjm5y3
http://tinyurl.com/k7o3l3q
Note that these devices, while 'rated' at some
value like 100A, they will CARRY 2x their
rated current almost indefinitely. At the
same time, when subjected to a hard fault
of 5 to 10x rated current, they open in tens
of milliseconds.
Legacy design goals for aircraft suggest that
this extension of the bus up to your panel
mounted circuit breaker needs a 'current limiter'
but not like the devices cited above. It's
much smaller and designed to protect the longer
run of wire to the breaker. Protection with
a response many times longer than the breaker
it feeds.
This question came up on the List a few years
ago . . .
Q: Drawing Z24 shows how to add an OV protection module for an
internally regulated power
supply. It requires the use of a 5A circuit breaker and also of a
fuselink attached to the main
connection of the main bus. The question: Can we replace the fuselink
by using one of the
outputs on the main bus protected by a larger fuse (say 15amps)? I
would like for sure the
breaker to let go before the fuse.
A: Some 5A breakers will open a 15A fuse. Fuses are MUCH faster than
breakers. This is
why I prefer the fusible link
The risks of positioning fuses upstream of breakers
is illustrated in the accident case I chronicled
here
http://tinyurl.com/msfmldj
and demonstrated here
http://tinyurl.com/ppdv5fg
The automotive world has used fusible links
in this capacity for decades and they've
served well in the capacity of mini-limiters.
Bob . . .
Message 4
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| Subject: | FYI - LMR195 coax |
I installed a new antenna on the roof yesterday
and wired it to the radio with LMR195 coax. While
this stuff has appealing performance specs, it is
NOT a drop-in-replacement for the legacy coaxes
that feature one or more braided outer conductors.
Emacs!
Unlike the RG142 illustrated above I found that the
braid wires on this coax are very small and few. The
coax's shield performance is bounded by the foil shield.
The outer braid is just a means by which connection can be made to
the foil and is relatively fragile compared to the
two heavy layers of braid in RG142/400
The installer must take extra care in the 3rd cut and
removal of the outer jacket so as not to damage
the braid.
Further, the 2nd cut designed to remove the shield
from a stub of center insulation is problematic.
Again, depth of cut and subsequent removal of the
foil shield (tightly bonded to the insulation)
is tricky.
I got my connectors installed and the feed line performs
as expected . . . but I would caution builders to work
with some scraps of this coax and some 'training
connectors' to refine their technique. I'll put
LMR195 coax termination on the list of comic books to be
crafted for the website.
Bob . . .
Message 5
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| Subject: | Re: Fusable link |
So a ANL current limiter off the main battery protecting the whole system would
not be a bad idea ?
John
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=423017#423017
Message 6
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| Subject: | Re: Fusable link |
At 01:21 PM 5/8/2014, you wrote:
><jmtipton@btopenworld.com>
>
>So a ANL current limiter off the main battery protecting the whole
>system would not be a bad idea ?
Not a bad idea . . . but not a good one either. Current
limiters have value for fault isolation in complex bus
structures . . . which are generally not found in Part
23 airplanes.
The fat wires between battery, main bus and starter
terminal are usually of such robustness that any
fault to ground would be more likely to burn a hole
in fault location as opposed to opening any limiter
in the path.
Single light TC aircraft have never been fitted with
such protection that I know of.
Bob . . .
Message 7
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| Subject: | Re: Fusable link |
=0A=0AFrom: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>=0ATo:
aeroelectric-list@matronics.com =0ASent: Thursday, May 8, 2014 5:32 PM=0AS
ubject: Re: AeroElectric-List: Re: Fusable link=0A =0A=0A--> AeroElectric-L
ist message posted by: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric
.com>=0A=0AAt 01:21 PM 5/8/2014, you wrote:=0A>--> AeroElectric-List messag
e posted by: "JOHN TIPTON" =0A><jmtipton@btopenworld.com>=0A>=0A>So a ANL c
urrent limiter off the main battery protecting the whole =0A>system would n
ot be a bad idea ?=0A=0A- Not a bad idea . . . but not a good one either
. Current=0A- limiters have value for fault isolation in complex bus=0A
- structures . . . which are generally not found in Part=0A- 23 airpl
anes.=0A=0A- The fat wires between battery, main bus and starter=0A-
terminal are usually of such robustness that any=0A- fault to ground wou
ld be more likely to burn a hole=0A- in fault location as opposed to ope
ning any limiter=0A- in the path.=0A=0ANot sure what that means... ???
- =0A=0AIf it is "robust" wouldn't it carry enough current to blow the li
miter?=0AAre you suggesting that "welding/burning" aluminum does not draw a
lot of current?=0AHave you ever tested that hypothesis?=0A=0AEven if some
of the above is true, a current limiter still could provide some protection
=0Afrom a "hard" fault, could it not?=0A=0A-Jeff=0A=0A=0A- Single light
TC aircraft have never been fitted with=0A- such protection that I know
- - - - - - - - - - - - - -Matt Dralle, List Adm
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