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JLuckey(at)pacbell.net
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 Posted: Tue Jun 26, 2012 5:25 pm Post subject: What's wrong with this circuit? |
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Bob,
What's the failure you're trying to
make tolerable?
Mechanical failure of feed lines from a batt contactor to distribution panel (in instrument panel). One possibility: a lug cracking and breaking loose and going to ground. (I’ve seen this one) I’m sure I could dream-up a few other scenarios…(likelihood is really the question)
What are the cost, weight, energy
benefits ratios for diode isolation versus hard-contacts
isolation?
I see the $ cost as acceptable; the additional weight as minimal; the wasted energy as insignificant;
I see the “automatic” nature of this protection as a big plus.
-Jeff
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert L. Nuckolls, III
Sent: Tuesday, June 26, 2012 17:49
To: aeroelectric-list(at)matronics.com
Subject: RE: AeroElectric-List: What'w wrong with this circuit?
At 06:41 PM 6/26/2012, you wrote:
There are certainly “intelligent” charge dividers available
Can you cite such a product we can see on the 'net?
I'm not sure I know what these devices are . . .
but in this case I’m thinking about something much more “old-fashioned” – like a couple of diodes in the output of the alternator which isolate the 2 batteries from each other. I will scribble a schematic when time permits.
You might wish to fold ideas in this article
into your deliberations.
http://tinyurl.com/77sf9sx
http://tinyurl.com/78lg7kf
http://tinyurl.com/7lhbbah
What value do you see for solid-state isolation of
batteries? What's the failure you're trying to
make tolerable? What are the cost, weight, energy
benefits ratios for diode isolation versus hard-contacts
isolation?
01234567890123
No virus found in this message.
Checked by AVG - www.avg.com
06/26/12 [quote][b]
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JLuckey(at)pacbell.net
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| Posted: Tue Jun 26, 2012 5:30 pm Post subject: What's wrong with this circuit? |
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Can you cite such a product we can see on the 'net?
I'm not sure I know what these devices are . . .
Charge Dividers:
http://www.philippi-online.de/index.php5?url=produkte.php5&m1id=2&sprache=en&kat1_nr=2&kat2_nr=2
http://www.ludomcgurk.com/charge-divider-1-product-32.html
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert L. Nuckolls, III
Sent: Tuesday, June 26, 2012 17:49
To: aeroelectric-list(at)matronics.com
Subject: RE: AeroElectric-List: What'w wrong with this circuit?
At 06:41 PM 6/26/2012, you wrote:
There are certainly “intelligent” charge dividers available
Can you cite such a product we can see on the 'net?
I'm not sure I know what these devices are . . .
but in this case I’m thinking about something much more “old-fashioned” – like a couple of diodes in the output of the alternator which isolate the 2 batteries from each other. I will scribble a schematic when time permits.
You might wish to fold ideas in this article
into your deliberations.
http://tinyurl.com/77sf9sx
http://tinyurl.com/78lg7kf
http://tinyurl.com/7lhbbah
What value do you see for solid-state isolation of
batteries? What's the failure you're trying to
make tolerable? What are the cost, weight, energy
benefits ratios for diode isolation versus hard-contacts
isolation?
01234567890123
No virus found in this message.
Checked by AVG - www.avg.com
06/26/12 [quote][b]
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Tue Jun 26, 2012 5:57 pm Post subject: What's wrong with this circuit? |
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At 08:24 PM 6/26/2012, you wrote:
| Quote: | Bob,
What's the failure you're trying to
make tolerable?
Mechanical failure of feed lines from a batt contactor to distribution panel (in instrument panel). One possibility: a lug cracking and breaking loose and going to ground. (I’ve seen this one) I’m sure I could dream-up a few other scenarios…(likelihood is really the question) |
But doesn't the dual feed e-bus take care of
this exceedingly unlikely scenario? A cracked
lug and/or bus going to ground speaks of poor
materials and craftsmanship. I've never seen this
become a worry to be addressed by design changes.
Dual batteries with and dual-feed e-bus pretty
much covers it . . . and doesn't hide anything
from the pilot by making failure mitigation
'automatic'. So just suppose the bus does go
dark? How long does it take to get on line with
an adequate suite of gear for continued flight
by flipping a couple of switches?
Just run electrically dependent engines from dual
sources, at least one of which is a battery bus.
Low volts light ON. Turn alternator off and
then exercise your plan-B designed to deal with
this event. The last high current feeder going
to ground I heard of at HBC was a King Air on
short final who was suddenly deprived of elevator
control.
Go-around was followed by un-eventful landing using
elevator trim. Found re-routed wire under co-pilot's
floorboard that rubbed against elevator cable. This
soft-fault eroded away the steel cable over many hours
of operation while doing little damage to the copper
wire. No smoke, no flashing lights, no smells . . .
It was one for the books. Bottom line is that
good craftsmanship with suitable materials makes
your fat-wires about as reliable as prop-bolts.
Bob . . . [quote][b]
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JLuckey(at)pacbell.net
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| Posted: Tue Jun 26, 2012 7:32 pm Post subject: What's wrong with this circuit? |
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My comments are mixed in below…
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert L. Nuckolls, III
Sent: Tuesday, June 26, 2012 18:56
To: aeroelectric-list(at)matronics.com
Subject: RE: AeroElectric-List: What's wrong with this circuit?
At 08:24 PM 6/26/2012, you wrote:
Bob,
What's the failure you're trying to
make tolerable?
Mechanical failure of feed lines from a batt contactor to distribution panel (in instrument panel). One possibility: a lug cracking and breaking loose and going to ground. (I’ve seen this one) I’m sure I could dream-up a few other scenarios…(likelihood is really the question)
But doesn't the dual feed e-bus take care of
this exceedingly unlikely scenario? A cracked
lug and/or bus going to ground speaks of poor
materials and craftsmanship. I've never seen this
become a worry to be addressed by design changes.
Dual batteries with and dual-feed e-bus pretty
much covers it
I don’t think I’m totally convinced of the benefit of multiple busses, main & essential. In my airplane almost everything is essential (except perhaps lighting & a few accessories). My list of essential stuff: Electronic Ignition, fuel pump, regulator, EFIS, at least one nav/com, transponder. Everything else is either not used frequently (like pitot heat) or has very minimal draw where a minute or two delay in turning-off the item is not significant.
With the single main bus that is essentially wired like a UPS (uninterruptible power supply) it seems simpler from an operational standpoint.
. . . and doesn't hide anything
from the pilot by making failure mitigation 'automatic'.
Not to confuse automatic w/ unknown – In this scenario, the system would produce a “Low Batt B Volts” alarm. (and a quick look at the Batt B voltmeter would indicate not only low but zero).
So just suppose the bus does go
dark? How long does it take to get on line with
an adequate suite of gear for continued flight
by flipping a couple of switches?
Just run electrically dependent engines from dual
sources, at least one of which is a battery bus.
Low volts light ON. Turn alternator off and
then exercise your plan-B designed to deal with
this event. The last high current feeder going
to ground I heard of at HBC was a King Air on
short final who was suddenly deprived of elevator
control.
Go-around was followed by un-eventful landing using
elevator trim. Found re-routed wire under co-pilot's
floorboard that rubbed against elevator cable. This
soft-fault eroded away the steel cable over many hours
of operation while doing little damage to the copper
wire. No smoke, no flashing lights, no smells . . .
Un-authorized arc welding (while airborne), very scary!
It was one for the books. Bottom line is that
good craftsmanship with suitable materials makes
your fat-wires about as reliable as prop-bolts.
agree, there is no substitute for quality components properly installed.
Bob . . . | Quote: | | http://www.matronics.com/Navigator?AeroElectric-List |
01234567
No virus found in this message.
Checked by AVG - www.avg.com
06/26/12 [quote][b]
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Wed Jun 27, 2012 9:45 am Post subject: What's wrong with this circuit? |
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At 10:30 PM 6/26/2012, you wrote:
I don’t think I’m totally convinced of the
benefit of multiple busses, main & essential. In
my airplane almost everything is essential
(except perhaps lighting & a few
accessories). My list of essential stuff:
Electronic Ignition, fuel pump, regulator, EFIS,
at least one nav/com, transponder. Everything
else is either not used frequently (like pitot
heat) or has very minimal draw where a minute or
two delay in turning-off the item is not significant.
Actually, it's not a 'essential bus' but an 'endurance bus'.
It's a means by which one can reduce loads on a battery to
the useful necessities for continued flight in the en route
mode. The idea is to design an electrical system with
endurance equal or greater than fuel aboard. This concept
goes to Plan-B for dealing with failure of the least reliable
energy source on the airplane . . . the alternator.
Suggest you review the chapter on system reliability and
List discussions on the philosophy and utility of the
E-bus . . .
Your 'concerns' are significant but may I suggest that
many are of such low risk as to be outside the sphere
of thought for designing your system? The hapless Mr.
Lloyd may have installed every back-up-to-backup system
in his airplane but all went for naught when wires pulled
out of terminal.
A search of FAA Service Difficulty Reports and NTSB accident
reports will show that very few accidents were precipitated
or exacerbated by electrical system failures. Those accidents
that DID have an electrical system component would have been
greatly mitigated by a combination of thoughtful architecture,
good preventative maintenance (don't run batteries 'til they
die) and pilot understanding of how the system worked.
The prime directives for this List are "thougtful architecture
that goes to comfortable tolerance of high risk failures",
"understanding based on simple ideas in physics, processes and
materials" and the study of "lessons learned from the experiences
of others".
With the single main bus that is essentially
wired like a UPS (uninterruptible power supply)
it seems simpler from an operational standpoint.
Simpler for the mitigation what failure for which there
is a demonstrably significant risk?
Not to confuse automatic w/ unknown – In this
scenario, the system would produce a “Low Batt B
Volts” alarm. (and a quick look at the Batt B
voltmeter would indicate not only low but zero).
But what is the risk for "zero volts" on a bus and
what elements make up the constellation of events that
might produce that event. Is it not better to first
reduce those risks by changes in design, process or
materials? After the ingredients that go into your proposed
recipe for success are carefully combed, only then do
you exercise tools necessary to craft a Plan-B for the
failure that might put the mission (or hygene in your
shorts) at risk.
The goal is to comfortably assert that "my airplane
is exceedingly unlikely to suffer an electrical
emergency. It may suffer many failures of components
for which I will suffer the expense of maintenance . . .
but any and all will be no-sweat events."
Un-authorized arc welding (while airborne), very scary!
Scary to contemplate but in reality, so 'gentle' that
it took many flight hours for the effects to achieve
the interesting conclusion. The fact that there was
a Plan-B in the pilots hip pocket paired to other
features of the airplane's architecture turned a
'scary' contemplation into a 'no sweat' event.
Bob . . .
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