Today's Message Index:
----------------------
1. 06:32 AM - Re: fuse or breaker for OVP? (user9253)
2. 06:41 AM - Re: fuse or breaker for OVP? (Bob McCallum)
3. 08:16 AM - Re: Overvoltage crowbar availability? (Robert L. Nuckolls, III)
4. 09:27 AM - Re: fuse or breaker for OVP? (Robert L. Nuckolls, III)
5. 09:43 AM - Re: Re: Alternator Disconnect Z17 vs Z20... (Robert L. Nuckolls, III)
6. 09:52 AM - Re: fuse or breaker for OVP? (Ken Ryan)
7. 10:00 AM - Re: fuse or breaker for OVP? (Robert L. Nuckolls, III)
8. 10:03 AM - Re: fuse or breaker for OVP? (Robert L. Nuckolls, III)
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Subject: | Re: fuse or breaker for OVP? |
Here is a link to the book:
http://www.aeroelectric.com/Book/AEC_R12A.pdf
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=435682#435682
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Subject: | fuse or breaker for OVP? |
Here it is.
http://www.aeroelectric.com/Book/AEC_R12A.pdf
Bob McC
_____
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Jim Kale
Sent: Friday, December 12, 2014 11:56 PM
Subject: RE: AeroElectric-List: fuse or breaker for OVP?
I'd like to down load "the book" if anyone can tell me what it is????
Jim Kale
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Charlie
England
Sent: Friday, December 12, 2014 5:39 PM
Subject: Re: AeroElectric-List: fuse or breaker for OVP?
I'm not Jeff, but,
A very short length (4"-6") of wire will carry much more current than its
'rated' capacity (which is for much longer lengths), and that's the basis on
which the fusible link idea arises.
Fusible links are common in cars these days for wire runs that have a very
low likelihood of overcurrent due to their load, but still need to be
protected from catastrophic faults (like pinched insulation causing a short
to ground). You can buy silicone-protected fusible link wire in bulk on line
in various sizes for protecting heavier wire. Common practice is to make the
link smaller by 4 numbers than the wire it protects (a 16ga link protects a
12ga wire). Like a fuse or breaker, it should be placed on the current
source end of the wire. Properly installed, they are much less prone to
defect-induced failure than circuit breakers or fuses (and much, much
cheaper than a/c circuit breakers). Somewhere in 'the book' you should find
a reference to making your own fusible link. It basically amounts to
sliding a woven fiberglass sleeve over the smaller gauge wire link and the
joint between link & wire. Download the book in digital form & use Acrobat
Reader's search function to find the references. If that isn't clear, just
ask for more detail.
Charlie
On 12/12/2014 4:27 PM, Ken Ryan wrote:
Thanks Jeff. Your reply is very helpful. I am developing schematics, but
have no easy way of scanning them. My system (Rotax) will have two engine
driven current producers. One of them is a more traditional alternator with
the internal regulator, and the other a permanent magnet affair with an
external regulator that the Z diagrams like to refer to as a "Dynamo."
I understand how the over voltage protection device is (differently) wired
for each of these two current producers, how for the alternator it cuts the
field circuit and for the dynamo it disconnects the regulator.
But I was unaware that the use of the OVP device eliminates the need for a
breaker in the high current charging wire. Now, looking again at the Z
drawings, I see that the "fuse" in the high current alternator wire is
marked by "note 10" which makes reference to something called a "fuse like
device called a current limiter."
How is this "current limiter" different from a fuse or breaker and why is it
preferable to a fuse or breaker?
Now, when I look at the Rotax specific drawing, I see the high current wire
from the "dynamo" seems to be protected by a 16 gauge fusible link. The
"dynamo" is rated at 22 amps. Is the 16 gauge fusible link up to the task?
Why would I want to use a fusible link, rather than a fuse or a breaker?
Ken
On Fri, Dec 12, 2014 at 12:18 PM, Jeff Luckey <jluckey@pacbell.net> wrote:
Ken,
To answer your question directly: Yes, it's okay to use a fuse w/ an OVM. It
will just be more difficult to reset ( and it does not give you a convenient
way to turn-off the alternator ).
However, I'm not sure I'm following you...
The best way to shut-down a standard, externally-regulated alternator is to
turn-off its regulator. The regulator usually draws less than 1 amp, so you
will commonly see a 1 or 2 amp Tyco Series 23 circuit breaker feeding the
regulator. Like this:
Image removed by sender.
The Over Voltage Modules we've been talking about are designed to create a
short circuit on the field breaker when high voltage is present, thus
popping it and shutting-down an errant regulator/alternator.
In this scenario, there is no big circuit breaker in the output of the
alternator because it's not needed. The output of the alternator is
controlled by the regulator & its circuit breaker. (And therein lies the
beauty of this system: no big breaker required and no big wires running to
that breaker in the panel.)
So, I'm a little confused by your question: "... Would it be okay to use the
bigger breaker in the charging circuit to accomplish a manual shutdown?"
Perhaps I'm missing something? Are you referring to one of BobN's Z
drawings? Do you have a schematic of the system you are talking about? (a
schematic is worth a thousand words)
-Jeff
On Friday, December 12, 2014 8:23 AM, Ken Ryan <keninalaska@gmail.com>
wrote:
Thanks Jeff. Are you saying that it would be okay to use the OVP device to
blow a fuse? Would it be okay to use the bigger breaker in the charging
circuit to accomplish a manual shutdown?
On Thu, Dec 11, 2014 at 9:28 PM, Jeff Luckey <jluckey@pacbell.net> wrote:
The idea behind feeding the Regulator with a circuit breaker is that it
gives the pilot the ability to shut-down the alternator (by pulling the
breaker) if that becomes necessary.
A few reasons you might want to shut down the alternator are:
1. a failed regulator that is giving full field (if you don't have an over
voltage module)
2. a failed over-voltage module
3. testing purposes
A breaker is simply more practical in this situation.
On Thursday, December 11, 2014 3:35 PM, Ken Ryan <keninalaska@gmail.com>
wrote:
I read on another forum that the B&C over voltage protection thingy must
only be used to trip a breaker, not to blow a fuse. Yet, I just re-read the
chapter on over voltage protection and did not see that mentioned. So the
question is, should the OVP device be used to: a) trip a breaker b) blow a
fuse c) either is okay ?
www.aeroelectric.com<www.buildersbooks.comwww.homebuilthelp.comwww.mypilotst
ore.comwww.mrrace.com
<http://www.matronics.com/contribution> http://www.matronics.com/c
-Matt Dralle, List - The AeroElectric-List Email List utilities such
as List Photoshare, and much much -->
http://www.matronics.com/Navigator?AeroElectric-List
http://forums.matronics.com====
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Subject: | Re: Overvoltage crowbar availability? |
At 20:43 2014-12-11, you wrote:
>
>Greetings,
>
>It looks like B and C no longer carries the stand-alone overvoltage
>crowbar (at least I think that's where I bought the one in my LongEz).
>I know Bob is trying to get out of the parts distribution business.
>Does anyone else know of a source or should I just plan on building
>my own. (and if you have the link handy to Bob's schematic that
>would be great but don't search if you don't as I'm sure I can find it...).
There is a replacement for the legacy crowbar modules
in the works. Boards are laid out and software is
nearly complete. Probably have some working hardware
in the next two weeks. B&C can probably still sell you
the older version as well.
The new one is software based and much more immune
to nuisance trips. It's also packaged to look more
like an 'airplane part' than the legacy CBOVM
modules.
Emacs!
Bob . . .
Message 4
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Subject: | Re: fuse or breaker for OVP? |
At 17:38 2014-12-12, you wrote:
>I'm not Jeff, but,
>
>A very short length (4"-6") of wire will carry
>much more current than its 'rated' capacity
>(which is for much longer lengths), and that's
>the basis on which the fusible link idea arises.
>Fusible links are common in cars these days for
>wire runs that have a very low likelihood of
>overcurrent due to their load, but still need to
>be protected from catastrophic faults (like
>pinched insulation causing a short to ground).
>You can buy silicone-protected fusible link wire
>in bulk on line in various sizes for protecting
>heavier wire. Common practice is to make the
>link smaller by 4 numbers than the wire it
>protects (a 16ga link protects a 12ga wire).
>Like a fuse or breaker, it should be placed on
>the current source end of the wire. Properly
>installed, they are much less prone to
>defect-induced failure than circuit breakers or
>fuses (and much, much cheaper than a/c circuit
>breakers). Somewhere in 'the book' you should
>find a reference to making your own fusible
>link.=C2 It basically amounts to sliding a woven
>fiberglass sleeve over the smaller gauge wire
>link and the joint between link & wire. Download
>the book in digital form & use Acrobat Reader's
>search function to find the references. If that
>isn't clear, just ask for more detail.
It's not described in the book . . . but a search at
aeroelectric.com on "fusible link" will produce a
comic book on its fabrication . . .
Bob . . .
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Subject: | Re: Alternator Disconnect Z17 vs Z20... |
Greetings,
I'm currently working on wiring up a Quickie with a Rotax 503 (and a
glass panel, go figure...). The two architecture diagrams that look
appropriate to start from are Z17 "Small Rotax System" (sounds right...)
and Z20 "Small Jabiru System".
They are basically the same EXCEPT they way the alternator is
disconnected (Z17 is downstream of regulator, Z20 is upstream of the
regulator).
I might be mistaken (please correct me...) but it also appears both
diagrams are assuming more of a diode bridge than a real regulator as
they both show a 20,000uF cap on the output of the regulator.
All z-figures for permanent magnet alternators depict
rectifier/regulators as the device of choice for
converting the PM alternator's output to DC and then
controlling it in a manner friendly to batteries and
avionics. Specifications for the 503 state:
GENERATOR OUTPUT: 170 W AC at 6000 rpm and 13.5 V RMS
RECTIFIER- REGULATOR: (optional) a.) #9103 requires min. load 12 W (1
amp) to regulate
b.) #9251 requires no min. load
Are you planning to use one of these two rectifier/regulators
or some other product? 170 watts of output probably translate
to about 14A maximum available output from the r/r . . . do
you plan electric start? Have you conducted a load
analysis of all planned accessories to determine
that you have enough engine driven power to support
the load?
My questions: 1) What's the significance, if any, of the different
approaches to the alternator disconnect?
None
2) If I use Rotax 264 870 regulator (as opposed to the 866 080
bridge) is the cap still appropriate (it's not shown in Rotex's
wiring diagrams?
Where might I find data on these two products? They're
not cited as one of the two options in the spec sheet I
downloaded. I'm not sure why anyone would ever use an
ordinary bridge rectifier between their PM alternator
and any other accessory. Can you point me to any literature
that describes/recommends this?
The capacitor has been a legacy feature of Rotax installations
on airplanes for decades. But the little testing I've been
able to do on PM alternators and rectifier/regulators cannot
confirm the value of adding this device. I'm planing to
get another look at the question with more sophisticated
equipment in the not too distant future.
Bob . . .
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Subject: | Re: fuse or breaker for OVP? |
On something like a generator charging wire that is connected to the
battery, since either end of the wire can be the power source, would it
make sense to put a fusible link at each end of the wire?
On Sat, Dec 13, 2014 at 8:22 AM, Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
>
> At 17:38 2014-12-12, you wrote:
>
> I'm not Jeff, but,
>
> A very short length (4"-6") of wire will carry much more current than its
> 'rated' capacity (which is for much longer lengths), and that's the basis
> on which the fusible link idea arises.
> Fusible links are common in cars these days for wire runs that have a ver
y
> low likelihood of overcurrent due to their load, but still need to be
> protected from catastrophic faults (like pinched insulation causing a sho
rt
> to ground). You can buy silicone-protected fusible link wire in bulk on
> line in various sizes for protecting heavier wire. Common practice is to
> make the link smaller by 4 numbers than the wire it protects (a 16ga link
> protects a 12ga wire). Like a fuse or breaker, it should be placed on the
> current source end of the wire. Properly installed, they are much less
> prone to defect-induced failure than circuit breakers or fuses (and much,
> much cheaper than a/c circuit breakers). Somewhere in 'the book' you shou
ld
> find a reference to making your own fusible link.=C3=82 It basically amo
unts to
> sliding a woven fiberglass sleeve over the smaller gauge wire link and th
e
> joint between link & wire. Download the book in digital form & use Acroba
t
> Reader's search function to find the references. If that isn't clear, jus
t
> ask for more detail.
>
>
> It's not described in the book . . . but a search at
> aeroelectric.com on "fusible link" will produce a
> comic book on its fabrication . . .
>
>
> Bob . . .
>
> *
>
===========
m>
ldersbooks.com>
.com>
com>
om/contribution>
===========
www.matronics.com/Navigator?AeroElectric-List>
===========
===========
>
> *
>
>
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Subject: | Re: fuse or breaker for OVP? |
At 17:35 2014-12-11, you wrote:
>I read on another forum that the B&C over voltage protection thingy
>must only be used to trip a breaker, not to blow a fuse. Yet, I just
>re-read the chapter on over voltage protection and did not see that
>mentioned. So the question is, should the OVP device be used to: a)
>trip a breaker b) blow a fuse c) either is okay ?
Either device will function as-intended . . . open the
alternator field circuit when an ov condition is detected.
Suggest you review the discussions unique to "crowbar"
ov protection on aeroelectric.com
http://tinyurl.com/q48agpd
You will discover both the reasoning behind adoption
of this technique along with recommendations for
its use on your airplane.
If your project includes a circuit breaker
panel, then the choice for fuse vs. breakers
is moot. If your choice of circuit protection
leans toward fuses, then the breaker is
recommended for (1) convenient inflight reset
(ONLY ONE TIME) in case of a nuisance trip,
(2) ground maintenance operations where you'd
like to stop a non-rotating alternator from
draining the battery. The later is applicable
only if you use the simple, two-pole, two-position
DC master that brings battery and alternator on
at the same time. If you choose to use the
three-position, on-on-on switch shown on various
z-figures, OFF, BAT, BAT+ALT then the pullable
breaker for ground ops is not necessary.
But in terms of OV protection, either fuse
or breaker will do the job.
Bob . . .
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Subject: | Re: fuse or breaker for OVP? |
At 11:47 2014-12-13, you wrote:
>On something like a generator charging wire that is connected to the
>battery, since either end of the wire can be the power source, would
>it make sense to put a fusible link at each end of the wire?
Not normally needed. An alternator is magnetically
incapable of blowing it's own b-lead protection.
You need protect only the battery-end of the
b-lead.
Bob . . .
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