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nuckolls.bob(at)aeroelect
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 Posted: Sat May 06, 2017 6:20 am Post subject: Overvoltage event (non-lithium battery) |
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At 12:17 PM 5/5/2017, you wrote:
| Quote: | --> AeroElectric-List message posted by: "bobmeyers" <bobmeyers(at)meyersfamily.org>
Bob,
Have you ever commented on these little guys. They are resettable breakers that fit into an ATC slot.
http://tinyurl.com/n4fem4d
I used fuses in my first build and also in my second build. I have looked at these as a natural fit for alternator field power.
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The narrative that goes with this product is
interesting . . .
Low profile ATO / ATC circuit breakers are single pole thermal overload type circuit protection devices. They can be used in many automotive, marine, and industrial applications. Low profile breakers are ideal when space is limited and for replacing fuses on your critical accessories[/i]. Commonly considered a type-3 thermal breaker, these can fit into most ATO / ATC fuse panels. Each breaker is color-coded by amperage according to automotive industry standards. Anyone who has conducted an FMEA on their
'critical accessories' knows that there are
many more failure modes that DO NOT open
the breaker than failure modes that DO
open the breaker. They should also know
that an open breaker probably announces
a fault that will not be cured by resetting
the breaker.
Suitability to task upstream of a crowbar
ov module is not clear. The miniature
breakers common to aircraft installations
are tested for ability to open multiple
'hard faults'. Here's one example of a
breaker not suited to the task as discovered
by a builder here on the List . . .
http://tinyurl.com/mqjz523
I cannot offer a learned opinion without
further evaluation and testing of this product's
construction. Another point in the list of
design goals says that using this breaker
in the crowbar ov system encourages positioning
the fuse panel in reach of crew during flight . . .
another practice which I discourage. See:
http://tinyurl.com/lvwnwkx
Bob . . .
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user9253
Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan
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| Posted: Sat May 06, 2017 9:31 am Post subject: Re: Overvoltage event (non-lithium battery) |
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Speaking of some circuit breakers that are not suitable to the task, I can vouch for that. I purchased a Schurter 3 amp circuit breaker, part number
4400.0010 to protect an over-voltage relay circuit. Before installing it in the airplane, I tried it out on the workbench. Instead of tripping when the crowbar circuit shorted out, the breaker continued to conduct and smoked. Although the smoke was not enough to be a hazard, it could be enough to distract a pilot and contribute to an incident.
I have a whole lot more confidence in fuses.
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Joe Gores |
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nuckolls.bob(at)aeroelect
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| Posted: Sat May 06, 2017 4:52 pm Post subject: Overvoltage event (non-lithium battery) |
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At 12:31 PM 5/6/2017, you wrote:
| Quote: | --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com>
Speaking of some circuit breakers that are not suitable to the task, I can vouch for that. I purchased a Schurter 3 amp circuit breaker, part number
4400.0010 to protect an over-voltage relay circuit. Before installing it in the airplane, I tried it out on the workbench. Instead of tripping when the crowbar circuit shorted out, the breaker continued to conduct and smoked. Although the smoke was not enough to be a hazard, it could be enough to distract a pilot and contribute to an incident.
I have a whole lot more confidence in fuses. |
To be sure, fuses have a certain finality in
the physics of their operation. Breakers can
too . . .
Some of you graybeards here on the List may
recall some terse discussions about the various
breaker options . . . especially when used
with crowbar ov protection.
Some off-hand numbers were offered a dire
predictions for failure-to-perform under
extreme fault conditions. I did some bench
demonstrations that measured much more
benign conditions than 'predicted' along
with citations from a military test
protocol by which our favorite breakers
are judged.
[img]cid:.0[/img]
These guys are tested under conditions far more
severe than those impressed upon it with
a crowbar ov protection system.
Beech agreed with this assessment too . . . a
few years back. I very nearly got crowbar ov
protection onto the Beech Lightning, a single
engine turboprop. Program go canceled about
the same time Burt Rutan left the employ of
Beech as VP of Engineering. He got the airplane
as part of his severance pay. I understand he
wanted the engine and instruments.
[img]cid:.1[/img]
I last saw the 'bones' of this project sitting outside
one of Burt's hangars on Mojave Airport. I had left
the employ of Electro-Mech by that time. I was no
longer involved in new alternator controller designs
for TC aircraft. I didn't get a chance to put
crowbar ov protection into airplanes until the series
of LR controllers at B&C. Two examples of which went
around the world with Dick and Jeana . . . and
now flys on thousands of both TC and OBAM aircraft.
But in any case, demands placed on the breaker
used with crowbar ov protection are beyond the
capability of some products. Fortunately, the
commercial clone of the military qualified
miniature breakers are quite suited to task.
Bob . . .
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Sat May 06, 2017 5:31 pm Post subject: Overvoltage event (non-lithium battery) |
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At 12:31 PM 5/6/2017, you wrote:
| Quote: | --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com>
Speaking of some circuit breakers that are not suitable to the task, I can vouch for that. I purchased a Schurter 3 amp circuit breaker, part number
4400.0010 to protect an over-voltage relay circuit. Before installing it in the airplane, I tried it out on the workbench. Instead of tripping when the crowbar circuit shorted out, the breaker continued to conduct and smoked. |
Was it you who sent me this breaker?
[img]cid:7.1.0.9.0.20170506201431.04e4a280(at)aeroelectric.com.0[/img]
I think it's a Schurter breaker. Uses a thin metal
'heater' to warm a bi-metal trip 'thermostat'. High
current faults would burn the strip before the thermostat
could sense and react.
Bob . . .
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user9253
Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan
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| Posted: Sat May 06, 2017 6:08 pm Post subject: Re: Overvoltage event (non-lithium battery) |
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It could have been me. My memory fades as I get older.
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Joe Gores |
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