Today's Message Index:
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1. 05:30 AM - Re: z13 battery bus protection (user9253)
2. 07:56 AM - Re: z13 battery bus protection (mmcelrea)
3. 10:32 AM - Re: z13 battery bus protection (user9253)
4. 11:04 AM - Re: Diy AOA, anyone ? (GTH)
5. 11:20 AM - Re: Re: z13 battery bus protection (Robert L. Nuckolls, III)
6. 11:28 AM - Re: z13 battery bus protection (user9253)
7. 03:22 PM - Re: Re: z13 battery bus protection (Robert L. Nuckolls, III)
8. 11:29 PM - Re: z13 battery bus protection (mmcelrea)
Message 1
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| Subject: | Re: z13 battery bus protection |
A fast blow fuse will INSURE that the essential bus IS taken out. Do not use a
fast blow fuse in series with the E-Bus no matter which end of the wire it is
located.
--------
Joe Gores
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http://forums.matronics.com/viewtopic.php?p=479393#479393
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| Subject: | Re: z13 battery bus protection |
Will a maxifuse not blow as fast as a normal blade fuse? Is a slow blow blade fuse
available?
The endurance bus feed wire from the hot battery bus is protected by a fuse at
one end and a fuselink at the other. Is it not acceptable to do the same with the
feed wire to the hot battery bus from the battery?
I would prefer to keep the simplest, most durable protection devices within the
engine compartment, ie a fuselink.
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http://forums.matronics.com/viewtopic.php?p=479396#479396
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| Subject: | Re: z13 battery bus protection |
On the Littlefuse website,
http://www.littelfuse.com/products/fuses/automotive-passenger-car/blade-fuses/299.aspx
it says, "MAXI 32V Series - MAXI Slo-Blo 32V Automotive Blade Fuse"
I assume that "Slo-Blo" means slow blow. The datasheet
http://www.littelfuse.com/~/media/automotive/datasheets/fuses/passenger-car-and-commercial-vehicle/blade-fuses/littelfuse_maxi_32v_datasheet.pdf
graph looks like the 30 amp fuse will hold 40 amps for several minutes without
blowing.
The reason that the endurance bus wire is protected at both ends is because there
are two current paths.
The wire needs to be protected from current coming from either end.
A maxifuse is a blade type fuse, but it is twice as big as ATX and ATO fuses.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=479397#479397
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| Subject: | Re: Diy AOA, anyone ? |
Le 16/04/2018 01:01, Robert L. Nuckolls, III a crit:
>
> We had some discussions here on the List about
> various AOA sensor/display options about 15 years
> ago. During and since that time I'd collected some
> articles on the topic which I posted here
>
> https://goo.gl/5XdU1y
>
> One of the articles cloned a sensor mast that
> was popular with Piper as I recall. Don't recall
> the manufacturer off hand.
Hi Bob and all,
A big thank you for your inputs, docs etc. !
We now have to do our homework. Nevertheless the project is still at the
initial build stage, and we are still in the process of (slowly)
reducing drag on our present 4-seater, so it may be some time til we are
ready for the AOA flight tests.
Thank you everyone !
--
Best regards,
Gilles
http://contrails.free.fr
http://lapierre.skunkworks.free.fr
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| Subject: | Re: z13 battery bus protection |
At 09:55 AM 4/17/2018, you wrote:
>
>Will a maxifuse not blow as fast as a normal blade fuse? Is a slow
>blow blade fuse available?
No . . . haven't got time right now to answer this
question carefully . . . but I will soon.
In the mean time, research the fault reaction time
curves for the devices being cited . . .
"Fast" and "slow" are un-quantified, squishy terms.
Bob . . .
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| Subject: | Re: z13 battery bus protection |
According to this chart:
http://www.litz-wire.com/New%20PDFs/Fusing_Currents_Melting_Temperature_Copper_Aluminum_Magnet_Wire_R2.011609.pdf
A #18 AWG fuselink will conduct up to 82 amps before it melts.
--------
Joe Gores
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http://forums.matronics.com/viewtopic.php?p=479400#479400
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| Subject: | Re: z13 battery bus protection |
At 09:55 AM 4/17/2018, you wrote:
>
>Will a maxifuse not blow as fast as a normal blade fuse? Is a slow
>blow blade fuse available?
No . . . and here's why . . .
Let's go to the engineering data for a sample of fuses
common to our designs. First the ATC10 plastic fuse
that fits the popular fuseholders . . . and probably
the largest fuse to be included on the battery bus
under consideration:
I have calculated a 'fusing constant' for this
fuse based on numbers taken from the ATC fuse
performance chart below. At approx 2x the 'carry
forever' current of the ATC10 fuse, it opens in
approx 0.4 seconds which produces an I(squared)T
value of 270. If we cause the fuse to carry twice
that value of 52A, we know that it will open in
approx ONE FOURTH that time or 0.1 seconds.
Double the current again to ~100A and we'll
anticipate fuse operation in ~0.05 seconds.
The chart below says it will be shorter still,
so perhaps my fusing constant number needs
trimming. Suffice it to say that the fusing
constant calculation carries an AMPS(SQUARED)
term in it suggesting that increasing current
shortens the operating time by 1/4th each doubling.
[]
[]
Now let us look at the 30A MaxiFuse. Note that
it has a much larger fusing constant (again perhaps
needing a tweak) but consider the operating time
at 100A. From the chart we read something on
the order of 3 SECONDS.
Suppose a MAX30 were protecting the battery
bus with a ATC10 fuse in it and you fault
that fuse with a 100A load. The ATC10 will open
many times faster than the MAX30 thus the
integrity of the bus feed is not at risk.
[]
Now, if we were protecting a SWITCHED bus in a TC
aircraft with similar distribution characteristics,
we might choose to use the ANL35 current limiter.
Note that its fusing constant is actually LESS
than the MAXI30. At 2x the ANL's carry forever
current, the fusing time is only 0.4 seconds. But
when loaded with our hypothetical fault of 100A
on an ATC10 fuse, the ANL35 is pretty close to
a never-operates condition.
[]
A take-away from this narrative has several points.
(1) 'Fast' and 'slow' are non-quantified, un-scientific
terms for evaluating performance of any circuit
protective device. You can say device A is faster
than device B under some cited conditions . . . but
that's about it.
(2) The fusing constant is useful for making some
broad predictions about performance between
two styles of product. For example, in the
charts about we see that Kf of 13K for the
ANL (a mechanically robust fuse compared to
the MAXI) is about 20x faster at the 2x
overload point than the MAXI with a Kf of 44K.
(3) I've not illustrated fusing characteristics
for the 18AWG fusible link . . . we know it's
going to be a BIG number. Now, considering that
the design goal for upstream protection of the
non-legacy battery bus is to MINIMIZE the
potential for expenditure of energy in a hard
fault condition, very robust devices like
fusible links are not consistent with the
design goal.
(4) The design goal calls for selection of an upstream
fuse with thermal characteristics consistent with
maintaining bus integrity under a downstream
BRANCH fault while minimizing energy expenditure
during a FEEDER fault.
(5) There is a significant simplification of the physics
in this narrative that does NOT consider PRE-
HEATING of the feeder protection due to normal
operating loads. Pre-heating figured heavily
in the demise of N811HB . . .
https://goo.gl/hWQdE6
I think I read the number 15A as the max running load
for this design. Assuming no branch fuse is greater than
10A . . . with most probably being smaller . . .
I'll s stand by my recommendation for a MAXI30 or
even a MAXI40 protecting a 10AWG feeder.
Having said that, I'd much rather the battery
bus was located near the battery.
The 30 Series aircraft at Beech have had fuses on the
firewall for decades
[]
Further, they were/are glass cartridge fuses (ugh!)
with threaded fasteners (fooey) . . . but I'm aware
of no problems with this design philosophy.
Bob . . .
Bob . . .
Message 8
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| Subject: | Re: z13 battery bus protection |
Bob, thankyou for your reply, much appreciated.
Miller
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=479419#479419
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