Today's Message Index:
----------------------
1. 07:06 AM - Tap into antenna coax? (Dr. Andrew Elliott)
2. 07:06 AM - Re: Re: Points for discussion OVP//more (Paul Messinger)
3. 07:08 AM - Echo in head sets with 2 ANR plugged in (Charles Heathco)
4. 07:37 AM - Re: Tap into antenna coax? (Dj Merrill)
5. 07:45 AM - Re: Tap into antenna coax? (Craig P. Steffen)
6. 07:59 AM - Re: Tap into antenna coax? (James E. Clark)
7. 07:59 AM - Re: Re: Points for discussion OVP//more (Robert L. Nuckolls, III)
8. 08:18 AM - Re: Tap into antenna coax? (Charlie England)
9. 09:03 AM - Re: Re: Points for discussion OVP//more (Ken)
10. 09:10 AM - Re: Tap into antenna coax? (Jerry Grimmonpre)
11. 09:56 AM - Re: Re: Points for discussion OVP//more (Robert L. Nuckolls, III)
12. 10:22 AM - Re: OV protection debate (Robert L. Nuckolls, III)
13. 10:45 AM - Re: White Paper on Crowbar OV Protection (Robert L. Nuckolls, III)
14. 10:47 AM - [Fw: [FlyRotary] Re: Alternators] (Charlie England)
15. 10:50 AM - Re: Using a 115 volt 400 hz device in a 12 (Robert L. Nuckolls, III)
16. 11:18 AM - Re: Re: care and feeding of batteries (Robert L. Nuckolls, III)
17. 12:46 PM - Re: Re: Subaru z-figure (Jon Finley)
18. 02:07 PM - Re: Alternators] (Robert L. Nuckolls, III)
19. 02:15 PM - Re: Tap into antenna coax? (Robert L. Nuckolls, III)
20. 06:21 PM - Re: Re: Crowbar OV Protection (Robert L. Nuckolls, III)
21. 06:44 PM - Re: Re: Points for discussion OVP//more (Dan O'Brien)
22. 07:42 PM - Re: Re: Crowbar OV Protection (Jerry Grimmonpre)
23. 08:14 PM - Re: LOCATION OF WX 500 ANTENNA (CHAD FELDPOUCH)
24. 08:36 PM - Re: Re: Crowbar OV Protection (Matt Prather)
25. 08:45 PM - Re: Re: LOCATION OF WX 500 ANTENNA (Jim Stone)
26. 08:58 PM - Re: relevancy redux (Robert L. Nuckolls, III)
27. 09:15 PM - Re: Re: Crowbar OV Protection (Robert L. Nuckolls, III)
28. 09:28 PM - (Paul Messinger)
29. 09:41 PM - Re: White Paper on Crowbar OV Protection (Robert L. Nuckolls, III)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Tap into antenna coax? |
--> AeroElectric-List message posted by: "Dr. Andrew Elliott" <a.s.elliott@cox.net>
I recently ripped out all the 25-30 year-old avionics in my plane and
installed a modern all-in-one box. Now I would like to semi-permanently
install a T-type tap at the antenna end of the coax for my primary comm.
The idea would be to have a second coax run going to the handheld I keep
for emergency backup.
Although it is fine in the local area, the heavily loaded short whip
antenna the handheld comes with doesn't work very well in cruise at
altitude, especially here in the SW where there are long stretches of
really empty country. Hooked to a regular comm antenna, though, it is
sufficient.
My planned use would be to have *either* the primary comm *or* the
backup radio turned on at any time, never both. Is this idea OK???
Will it work???
Andy Elliott
N481HY/AA-1(TD,160)/KFFZ
That's "One Hot Yankee"
http://members.cox.net/n481hy/
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Points for discussion OVP//more |
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
Thanks for your comment.
For the record I repeat what I have said in the past.
"Bob has contributed more than ALL the others combined for the homebuilders
electrical wiring systems"
That does not mean everything suggested should be used blindly nor is
everything the best in today's world.
I doubt that many realize the huge currents (and I have documented 400 amps
+ many times) that can be produced by the OVP and frankly likely with the LR
series of external regulators. I can find nothing suggestion the possibility
of such currents and the potential for side affects. As a extremely simple
mod reduces the peak current to reasonable values and does nothing to the
functionally of the OVP I simply find Bob's resistance strange to say the
least. 25 amps will pop the fuse nearly as fast without the potential side
affects.
You know I never gave Bob's OVP approach much thought until the load dump
testing we did last year. I never was a proponent of crowbars and NEVER
where the crowbar was used to short a hi current battery ALL my engineering
peers were astounded to find there was a non current limited crow bar being
used across a battery as none had ever seen or heard of such an application.
I would be surprises if anyone at Lance realized the specific currents
produced by the OVP in their blanket endorsement of Bob. BTW I have often
sent builders to Bob for design and building methods for their electrical
system with the exception of those with an electrically dependent aircraft
where Bob has not completely addressed the issues unique to an engine that
needs 10-20 amps just to run and cannot stand even momentary battery
terminal voltage under approx 11.0 V.
More on this in other past and future posts.
Paul
----- Original Message -----
From: "Dan O'Brien" <limadelta@gmail.com>
Subject: AeroElectric-List: Re: Points for discussion OVP//more
> --> AeroElectric-List message posted by: "Dan O'Brien"
> <limadelta@gmail.com>
>
>>Paul wrote:
>>A developer of a new avionics system who only looks at certificated
>> aircraft will not notice your design, nor will those who also inquire
>>with major experimental aircraft manufacturers like Vans.
>
> Hmm... the top composite experimental (Lancair) says in its IVP
> manual, its ES manual, and its recently updated Legacy manual (see
> http://www.lancair-kits.com/manual_revisions/Legacy_manual_rev-0105.pdf,
> p. 27-4):
>
> "Robert Nuckolls is also an excellent reference for wiring. He
> publishes a newsletter,
> The AeroElectric Connection, and also contracts his services to
> individual builders to design custom electrical schematics. He can be
> reached at:
>
> Medicine River Press
> 6936 Bainbridge Road
> Wichita, Kansas 67226-1008
> (316) 685-8617"
>
> While specifics of this may be slightly off or dated (is there a
> "newsletter" we don't know about beyond the website?), this is
> clearly an endorsement from a pretty big player in the experimental
> category. Yeah, Lancair is "small" compared to Vans, but I think it's
> number one among the more "modern" composite players. FWIW.
>
>
>
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Echo in head sets with 2 ANR plugged in |
--> AeroElectric-List message posted by: "Charles Heathco" <cheathco@comcast.net>
I noticed this problem a while back, but didnt tie it to the condition until second
time it was a factor. If Im alone, or psgr has non ANR headset, no problem.
Two ANR headsets and get a feedback type of echo when comm with each other.
I have a mono flight com 403. I think it is suspect and wondered if anyone else
had this problem.
Would an upgrade to say a sterio PS enginering eliminate this problem? charlie
heathco
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Tap into antenna coax? |
--> AeroElectric-List message posted by: Dj Merrill <deej@thayer.dartmouth.edu>
Dr. Andrew Elliott wrote:
> My planned use would be to have *either* the primary comm *or* the
> backup radio turned on at any time, never both. Is this idea OK???
> Will it work???
>
> Andy Elliott
Hi Andy,
I'd be concerned with the transmit power of the
first radio going directly into the receiver of the
second radio. Not sure if having it powered off would
be adequate, and if you ever accidentally left it
on you would likely fry the receiver in the other radio.
Narco used to make a relay device that let
you use two radios with one antenna. I have one
somewhere here in a box that I'd be willing to let go
relatively cheap ($20+s/h), but as I just moved most of my
life is still in a box, so I don't know exactly
where it is at present.
Rather than use the relay, I ended up installing
a second COM antenna. It was relatively cheap - I think
I paid around $70 for the antenna and the install was
easy. I helped with the installation in the Cessna 150
and I think the total bill was around $100.
-Dj
--
Dj Merrill
deej@thayer.dartmouth.edu
"TSA: Totally Screwing Aviation"
Message 5
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Tap into antenna coax? |
--> AeroElectric-List message posted by: "Craig P. Steffen" <craig@craigsteffen.net>
On Sun, Mar 20, 2005 at 08:04:46AM -0700, Dr. Andrew Elliott wrote:
> I recently ripped out all the 25-30 year-old avionics in my plane and
> installed a modern all-in-one box. Now I would like to semi-permanently
> install a T-type tap at the antenna end of the coax for my primary comm.
> The idea would be to have a second coax run going to the handheld I keep
> for emergency backup.
>
> My planned use would be to have *either* the primary comm *or* the
> backup radio turned on at any time, never both. Is this idea OK???
> Will it work???
NO. In general, this will not work.
For receiving, half the power of the incoming signal will go down each
of the branches. The loss of that much signal is probably tolerable,
but...
I don't know that transmitting would work at all. Say you're using
the primary radio, and nothing was plugged into the handheld line.
When the signal hits the T-fitting, part of the signal goes out the
antenna, and part of it goes down the other branch. It reflects off
the empty and, reflects back down it, and then goes out the antenna
_out of phase_. The physics of the wave propogation in the cable is
similar to sound propogation inside of a tube. If you cut a hole in
the side of a trombone and fasten on a 6 foot long piece of PVC pipe,
you'll still get sound out, but it won't be at the right pitch, and it
won't sound like a trombone.
If you have spare radio plugged in and you're using the primary radio,
it might work somewhat. I don't know how the receive part of a radio
is wired; it might have the termination resistor across the contacts
at all times, in which case it would absorb the reflections I
described above. However, at best, you're still only transmitting
half the energy of the primary radio out the antenna; half of it's
going into the handheld. And be absolutely sure that the termination
resistor in the handheld can absorb half of the transmitting power of
the primary radio.
It's possible that there's something that I'm missing, and it actually
would work, but I think it's very prone to messing things up and it's
unlikely to ever work quite right.
Craig Steffen
--
craig@craigsteffen.net
public key available at http://www.craigsteffen.net/GPG/
current goal: use a CueCat scanner to inventory my books
career goal: be the first Vorlon Time Lord
Message 6
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Tap into antenna coax? |
--> AeroElectric-List message posted by: "James E. Clark" <james@nextupventures.com>
Another option ...
King used to make an adapter for their KX99 Handheld that can be used.
Basically the mini jack/plug arrangement opens the coax from the panel and
closes the connection to the handheld. It is all done in a neat little box
and you get a mini->coax pigtail.
Don't know if they still sell them or not.
James
| -----Original Message-----
| From: owner-aeroelectric-list-server@matronics.com [mailto:owner-
| aeroelectric-list-server@matronics.com] On Behalf Of Dr. Andrew Elliott
| Sent: Sunday, March 20, 2005 10:05 AM
| To: aeroelectric-list@matronics.com
| Subject: AeroElectric-List: Tap into antenna coax?
|
| --> AeroElectric-List message posted by: "Dr. Andrew Elliott"
| <a.s.elliott@cox.net>
|
| I recently ripped out all the 25-30 year-old avionics in my plane and
| installed a modern all-in-one box. Now I would like to semi-permanently
| install a T-type tap at the antenna end of the coax for my primary comm.
| The idea would be to have a second coax run going to the handheld I keep
| for emergency backup.
|
| Although it is fine in the local area, the heavily loaded short whip
| antenna the handheld comes with doesn't work very well in cruise at
| altitude, especially here in the SW where there are long stretches of
| really empty country. Hooked to a regular comm antenna, though, it is
| sufficient.
|
| My planned use would be to have *either* the primary comm *or* the
| backup radio turned on at any time, never both. Is this idea OK???
| Will it work???
|
| Andy Elliott
| N481HY/AA-1(TD,160)/KFFZ
| That's "One Hot Yankee"
| http://members.cox.net/n481hy/
|
|
Message 7
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Points for discussion OVP//more |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 07:06 AM 3/20/2005 -0800, you wrote:
>--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
>
>Thanks for your comment.
>
>For the record I repeat what I have said in the past.
>
>"Bob has contributed more than ALL the others combined for the homebuilders
>electrical wiring systems"
>
>That does not mean everything suggested should be used blindly nor is
>everything the best in today's world.
>
>I doubt that many realize the huge currents (and I have documented 400 amps
>+ many times) that can be produced by the OVP and frankly likely with the LR
>series of external regulators. I can find nothing suggestion the possibility
>of such currents and the potential for side affects. As a extremely simple
>mod reduces the peak current to reasonable values and does nothing to the
>functionally of the OVP I simply find Bob's resistance strange to say the
>least. 25 amps will pop the fuse nearly as fast without the potential side
>affects.
<snip>
Please my friend, how did you get 400 amps? Let's postpone any discussions
about how the science is applied. Let's assume we're talking about fault
currents downstream of ANY over-current protection device be it fuse,
breaker or electro-whizzy. Let's assume the fault can come from a variety
of instances not the least of which are wires contacting the airframe
or even a crowbar ov module. Where would I "fix" the experiment cited
to approach the fault currents you're citing . . .
What I'm suggesting . . . and attempting to illustrate is the
detail level of understanding of underlying principals upon which
every product should be crafted irrespective of its application
or comparative performance with other products.
BTW I have often
>sent builders to Bob for design and building methods for their electrical
>system with the exception of those with an electrically dependent aircraft
>where Bob has not completely addressed the issues unique to an engine that
>needs 10-20 amps just to run and cannot stand even momentary battery
>terminal voltage under approx 11.0 V.
There are two separate issues here. Need to support an engine's
energy requirements and the need to maintain bus voltage above
some level for minimum performance of some product.
We already know of several popular products where the
designers have chosen to ignore or just didn't appreciate
the value of considering a wealth of tribal knowledge that
precedes their endeavors . . . not the least of which are
DO-160 recommendations. If a builder chooses to use these
products, separate battery support is required and it
doesn't matter who is the low voltage antagonist be
it starter motor, landing gear pump, air conditioner
drive motor, or crowbar ov protection module or a short
somewhere in the electrical system.
If one wishes to embrace these products as standard bearers
for "modern electronics" and overlook relaxation of
design goals for "yesterday's electronics", it's certainly
their right. These are experimental airplanes and I hope
the remain so for ever. The risk is that relaxation of
common practice for yesterday's electronics in today's
electronics may lead to further relaxation in tomorrow's
electronics. In my never humble opinion, this is not
progress or even maintenance of the best we know how to
do today.
I'm pleased to note that our friends down at Emagair
have crafted an ignition system that will allow one to
prop an engine using a battery that is too weak to even
close its own battery contactor. How cool is that?
Hey you guys at Slick . . . put that in your Unison pipe
and smoke it! Well, fooey. I jumped off the science
wagon myself and fell into the philosophy puddle
. . . my apologies.
I think it's important to bring our constituents up to
speed on the science before we analyze philosophy.
I'm posting the next revision to the science white paper
this afternoon sometime.
Bob . . .
Message 8
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Tap into antenna coax? |
--> AeroElectric-List message posted by: Charlie England <ceengland@bellsouth.net>
James E. Clark wrote:
>--> AeroElectric-List message posted by: "James E. Clark" <james@nextupventures.com>
>
>Another option ...
>
>King used to make an adapter for their KX99 Handheld that can be used.
>Basically the mini jack/plug arrangement opens the coax from the panel and
>closes the connection to the handheld. It is all done in a neat little box
>and you get a mini->coax pigtail.
>
>Don't know if they still sell them or not.
>
>James
>
snipped
You can make one of these for yourself if you're handy with a soldering
iron. Jim Weir actually described construction in an old Kitplanes article.
http://www.rst-engr.com/kitplanes/KP0203/KP0203.htm
The design won't make HAM radio guys or RF engineer types happy, but it
works fine considering the limited use it will get. If you're really
worried, put it in a little aluminum box.
Charlie
Message 9
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Points for discussion OVP//more |
--> AeroElectric-List message posted by: Ken <klehman@albedo.net>
There certainly isn't any automotive based stuff that doesn't run well
below 11 volts or many cars would never even start. If the goal is a
21st century power source then perhaps the systems that use electricity
should also catch up to the automotive world. Mine has because it is
automotive.
Ken
>BTW I have often
>sent builders to Bob for design and building methods for their electrical
>system with the exception of those with an electrically dependent aircraft
>where Bob has not completely addressed the issues unique to an engine that
>needs 10-20 amps just to run and cannot stand even momentary battery
>terminal voltage under approx 11.0 V.
>
>
Message 10
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Tap into antenna coax? |
--> AeroElectric-List message posted by: "Jerry Grimmonpre" <jerry@mc.net>
Would it work to tape a rubber ducky antenna outside a gear leg fairing to
test out the handheld for xmit/rec? If it worked it could then go inside
the fairing for more permanent use. Has anyone tried this?
Jerry
> Dr. Andrew Elliott wrote:
>
>> My planned use would be to have *either* the primary comm *or* the
>> backup radio turned on at any time, never both. Is this idea OK???
>> Will it work???
Message 11
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Points for discussion OVP//more |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 09:45 PM 3/19/2005 -0500, you wrote:
>--> AeroElectric-List message posted by: "Dan O'Brien" <limadelta@gmail.com>
>
> >Paul wrote:
> >A developer of a new avionics system who only looks at certificated
> > aircraft will not notice your design, nor will those who also inquire
> >with major experimental aircraft manufacturers like Vans.
>
>Hmm... the top composite experimental (Lancair) says in its IVP
>manual, its ES manual, and its recently updated Legacy manual (see
>http://www.lancair-kits.com/manual_revisions/Legacy_manual_rev-0105.pdf,
>p. 27-4):
>
>"Robert Nuckolls is also an excellent reference for wiring. He
>publishes a newsletter,
>The AeroElectric Connection, and also contracts his services to
>individual builders to design custom electrical schematics. He can be
>reached at:
>
>Medicine River Press
>6936 Bainbridge Road
>Wichita, Kansas 67226-1008
>(316) 685-8617"
>
>While specifics of this may be slightly off or dated (is there a
>"newsletter" we don't know about beyond the website?), this is
>clearly an endorsement from a pretty big player in the experimental
>category. Yeah, Lancair is "small" compared to Vans, but I think it's
>number one among the more "modern" composite players. FWIW.
Yes, this is VERY dated info but not particularly relevant.
This isn't a contest and there's no value in tallying up
votes for or against any particular philosophy or champion
of that philosophy.
I'm reminded of a plaintiff attorney who once made the
statement, "You guys only have two witnesses who stated
that the engineer blew the whistle and I have a dozen
witnesses to state that the engineer didn't blow the
whistle. Therefore I win by 12 to 2"
The statement illustrates the total lack of logic that
says just because a person does not perceive the
sound of the whistle, does not mean with certainty that
it did not blow. However, if only only one honorable
witness heard the whistle and testifies as to fact,
then without a doubt the whistle DID blow.
Lets focus on facts as deduced by repeatable experiment
and then build a philosophy on those facts.
Bob . . .
Message 12
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: OV protection debate |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 08:00 PM 3/18/2005 -0800, you wrote:
>--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
>
>I did testing that included all you seem to want in the Load Dump study.
>
>I setup a simple but complete electrical system (using real sized wiring and
>gauges) from battery to running alternator. For the OVP testing I tested 3
>different CB styles from 2 mfgrs to verify the data.
>
>I have several hundred photos and many pages of test results that are on the
>slow path to being on my web site.
Paul,
Please don't mistake my activity as a tool attempting to
flog you into action nor is it intended to chastise you for inaction.
Please take care of important business. We all have to make
decisions as to the best use of our most limited resource . . . $time$.
The effort I put into the current work probably wasn't so much
a better use of $time$ from perspective of return-on-investment
as opposed to a break from the frustrations of trying to design/fix
parts of certified ships while working within the mandated framework
of a committee . . . most of whom to not understand what I do.
Revision -B- to my paper will publish today . . . revision -C-
is some time in the future and perhaps even never. Please don't
react to it in any manner except as a critical reviewer capable
of spotting bogus science and errors.
<snip>
>I have taken a lot of heat from Eric on publishing the complete report but I
>have so little time and so much to do. Eventually is what #2 priority gets
>:-) If one only publishes parts there are unanswered questions that remain.
>Also I dislike to report in pure engineering terms as there are so few that
>would understand what I am saying and so many that need to hear it in
>general english.
Aw . . . tell Eric to get himself a beer and go out on
the deck with a good book. All good things will come
in due course. I agree on the hazards of trying to communicate
in the academic vernacular. My technical leader at RAC recommended
a paper on leadership to all of his subordinates about a week
ago. This thing was about 6 pages long and my eyes were glazed
over after the first page . . . I'm writing my own paper on
qualities of leadership which I will submit back to him and
ask for critical review. "Hey boss, how does the paper you
cited differ this one?" Mine is about done and is only 2 pages
long . . . and uses no words that the average engineer at
RAC should have to look up in the Dictionary of Vague Terms.
By all means, when your work IS ready for critical review,
please word it in a manner that all discussions leading out
of it can include the majority (if not all) of our friends here
on the List.
Bob . . .
> > Would it maybe not help solve some of this debate as to the OV
> > protection if perhaps Eric, Paul, and Bob all drew up their
> > favorite OV protection circuit, and maybe one or all of them
> > took the time to actually run them and produce a situation
> > that would cause trouble? I know Bob ran his circuit to
> > prove his....
No Tim, this wasn't the intent of the first issue of
the white paper . . . nor is it the intent of the
issue out today . . .
> > . . . but I'd be interested to see a couple of different
> > OV options, and graphs of voltage and current spikes that
> > happened when an OV condition was created. It seems like
> > all of this debating back and forth could be settled
> > with just a few hours of directly compared experiments...
We're working up to that. Far too much water has already
run under the bridge roiled up by bad science and
personal interpretations/emotions.
This is a multi-layered experiment . . . bottom layer
is the science of the philosophies offered. Several
other layers exist in between but the layer is an
experiment to offer readers of this list what I
hope is a valuable tool: An illustration of how any
useful philosophy worth adopting must be supported by good
science first.
Bob . . .
Message 13
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: White Paper on Crowbar OV Protection |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 07:43 PM 3/18/2005 -0800, you wrote:
>--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
>
>If the internal regulator gets all its power from the field lead then
>opening this lead stops the alternator output current. I have modified
>several brands to eliminate the internal "B" lead to regulator connection
>and then the only "B" lead protection is a fuse. Not easy to do on ND brand.
>
>GOOD alternator internal regulators have adequate load dump protection built
>in. Why Vans fail when coupled with OVP and not just Bobs is a mystery at
>present. Vans has no answer.
A KEY perception. Van's wasn't incorrect in their description
of circumstances surrounding the failure events . . . yes, the
alternators WERE fitted with b-lead disconnect contactors and
OV protection.
Further, their reaction is quite understandable. If
you stick your hand through a hole and pull back some bloody fingers,
the simplest remedy is to suggest "don't put your hand through that hole".
But if a useful feature of your airplane is accessed through that
hole, then you are encouraged to deduce what's wrong with the design on the
other side. For whatever reasons, Van's chooses not to join that
investigation and that's fine. It's not their venue of expertise
and things about which they choose to acquire expertise are done very well.
>However its not necessary to disconnect the "B" lead when the alternator is
>running except in a failure mode. It should never be done as a matter of
>testing in my opinion.
Agreed. In fact, a concern that has/needs to be investigated
is what happens to a failed alternator if the b-lead connector
is opened in response to regulation failure. It seems that it
would continue to run self-excited in the runaway mode and
probably smoke the field winding or short some diods. While an
b-lead disconnect will certainly save the rest of the system,
is their an elegant solution to keeping a $5 part in an alternator
from forcing the destruction of other perfectly good parts in
the alternator.
Bob . . .
> > Matt:
> > "If a device that simply opens the B lead is enough to damage the
> > alternator, it doesn't sound like the real reason is the OVP module
> > (although it is possible it could make a problem more likely). It
> > suggests to me that these alternators should not be disconnected at all
> > once running, and if you want the ability to do that maybe they are not
> > suitable. Of the thousands of aircraft flying without failures, how many
> > have tested what happens if the alternator is disconnected?"
Matt . . . very good question which I touched on above.
> >
> > I agree. The alternators that Van's sells probably are ones which
> > don't source the field current through the sense wire. They are probably
> > automotive derivative and as such, running without a battery wasn't one of
> > the design parameters.
>
> > Operationally, the risk of damage from a disconnect can probably be
> > minimized. Take actions which disconnect the b-lead only when the
> > loads and possible output are low. Don't cycle the alternator on a cold
> > night when all the lights are on and the engine is turning cruise RPM.
Correct. You wouldn't do this in your Cessna . . . why do it
in your RV?
> > Whether an alternator which supplies its field current through the control
> > wire should be installed with a b-lead contactor is debatable. If I use
> > an alternator that has internal regulator, it will have the contactor. I
> > don't know what the fail modes in the regulator are.. Is there another
> path for
> > excitation to get through?
The question would more properly focus on the b-lead to field
path internal to the alternator that works INSIDE the b-lead
disconnect barrier which precipitates further damage onto an alternator
after the regulator fails.
I've seen alternator schematics that show a zener diode downstream
of a fuse INTERNAL to but in series with the b-lead supply to the
field. The schematic didn't reveal component values but it suggests
a practical way to build some protection of the alternator field
into an alternator used with a b-lead contactor. If the voltage
after opening the b-lead contactor continues to rise (to some
value with healthy head-room - like 20-25 volts) then the zener
shorts and the fuse opens protecting the alternator from self
immolation.
Bob . . .
Message 14
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: [Fwd: [FlyRotary] Re: Alternators] |
--> AeroElectric-List message posted by: Charlie England <ceengland@bellsouth.net>
Bob,
This showed up on another list & some would like to see your comments,
since you are directly involved in certified hardware. I'm pretty sure I
could write more about the inconsistencies here than he's written about
the differences, but I'd also like to see your opinion. I'll post back
to the other list if that's acceptable.
Thanks,
Charlie
Begin quote:
From Pifer's Airmotive, Inc. Pontiac MI
DIFFERENCES BETWEEN AIRCRAFT & AUTO ALTERNATORS USING A FORD BELT DRIVEN 12v
OR 24v ALTERNATOR FOR A COMPARISON
1. Although alternators are bi-rotational, aircraft engines turn opposite of
automotive. This means cooling fans must be canted in the opposite direction.
Also, pulley and belt size vary due to coming-in speed.
2. The thru bolts are of a higher tensile strength utilizing an
anti-rotation
device in the form of a lock tab. The rectifier assembly has a heavy duty
diode with higher voltage and amp. capacity. Also, one excites at 90 PIV (Peak
Inverse Voltage) and the other at 150 PIV. Radio suppression is designed for
108 frequencies and up which is the VHF and 108 and down which is FM band.
3. The brushes have a higher graphite content and they utilize a tin plate
on
the brush leads to prevent corrosion.
4. The stator is of the Delta wind rather than the Y" wind and it does not
utilize the stator terminal. The aircraft unit also carries H" insulation
which is capable of 200 degrees centigrade temperatures. It also is rated at
60 amp. instead of 55.
5. The rotor has a shorter shaft and a smaller thread size. Because of the
opposite rotation it is wound in the opposite direction. It also uses "H
insulation and Havel varnish.
6. The front and rear housings are the same as automotive.
With this brief description, I hope I have enlightened you on the
differences
between aircraft and automotive alternators. Using automotive units in an
aircraft creates a potential safety hazard as well as a short alternator life
and unreliability.
End quote
Message 15
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Using a 115 volt 400 hz device in a 12 |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 09:37 PM 3/18/2005 -0600, you wrote:
>--> AeroElectric-List message posted by: Jerzy Krasinski
><krasinski@provalue.net>
>
>
> >
> > A few years hence, someone decided that we could eliminate
> > an expensive heavy drive system if devices requiring AC
> > power could be made to accept a wider range of frequencies.
> > Transformers can be designed with 400Hz windings and core
> > magnetics but fabricated from 1000Hz materials with respect
> > to losses and guess what? The thing runs fine over range
> > of 400-1000 Hz.
> >
> > This is the philosophy of choice for new systems design
> > and has been in place now for perhaps 20 years or more.
> >
> > Bob . . .
> >
> >
> >
>Bob,
>Just for curiosity, what frequency is generated by alternator (before
>rectification) in a typical Cessna in cruise conditions?
>Jerzy
It's been a very long time since I had a "scope" on an
alternator and (of course) the gear/pulley ratios between
crankshaft and alternator have a profound effect on the
frequency as does the number of poles in the stator and field.
I seem to recall measuring numbers in the 200-400 Hz range
for boss-hogg 100A Teledyne alternators on a big recip
Cessna Twin. I was looking at rewinding the alternators
with a lighter 28v winding and using the space opened up
to add a low current, 200 volt winding to bring
3-phase AC out for windshield heating. I don't recall the
exact numbers now but my best guess is perhaps 200 Hz
at ramp idle on a gear driven alternator up to a 1000 Hz
or more on a belt driven, small pulley alternator on the
front of a Lycoming at cruise.
After my test stand gets set up, I'll be able to get
some better and more current data.
Bob . . .
Message 16
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: care and feeding of batteries |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
<snip>
>Right. But I still hold that batteries need not fail in 18 months if
>properly treated.
Quantify "failure" . . .
I've had builders walk up to the B&C booth at OSH and extolling
the virtues of "a B&C's battery still going strong in my
airplane after 5 years". Bill was delighted that folks standing
at the booth took reverent notice . . . I had to bite my tongue.
The guy flying that five year old battery was able to crank
the engine to get the ship to OSH. Had he experienced an
alternator out condition on his way to OSH three years ago
he might well have considered the battery "failed" when
it didn't get him back on the ground comfortably.
> >> OTOH, there is no reason that a properly cared-for battery shouldn't
> >> provide 90% capacity at 5 years. If viewed that way the extra
> >> complexity starts to look like break-even. Hey, guys are buying the
> >> Unison/Slick electronic magneto system.
> >
> > Again, not enough data to support the premise. I have
> > "properly cared for" batteries in my shop that are well
> > over 5 years old. They're deep cycle batteries used in
> > instrumentation systems. Each one has been used to about
> > 50% capacity perhaps a dozen times. They sit on Battery
> > Tenders the rest of the time. If those batteries
> > were in constant use . . . say discharged to 50% twice a
> > week . . . I can guarantee that they'd be sent to the
> > recycling pile a couple of years ago.
> >
> > 100 deep discharge cycles spread over 5 years is 20 cycles
> > per year. One every two weeks. How often do you pull your
> > batteries down to less than 50% charge?
>
>On my boat? My normal daily cycle is about 25%-30% discharge. Every
>couple of months I pull them down to about 70% discharge to check that
>they are still delivering normal capacity. Deka claims that I should
>see 600 cycles to 80% discharge and 2100 cycles at 25% discharge. So I
>should still see something close to a 5 year life at these rates.
Boat and RV batteries are designed for deep cycle service as are
golf cart and fork lift batteries. The some of the Odyssey batteries are
thin plate, supper crankers and not as well suited to deep cycle
service. Bottom line is still that unless a battery user chooses
to TEST a battery periodically for capacity and compare that to
his/her individual requirements for capability, the true service
life of a battery is something of a crap-shoot.
I have to strongly protest non-quantified, non-specific
application advertisement of ANY battery . . . particularly
those touted for their cranking and cold-weather abilities.
There's more to running a railroad that shoveling coal into
the firebox and more to battery selection and maintenance
than picking one that gets that tired ol' untuned engine
running on a cold morning.
> >> It shouldn't be all that difficult. Three-stage charge regulators for
> >> the marine and RV markets are less expensive then the B&C VR by a long
> >> way. Some even include current and/or temperature sensing to limit
> >> the output of the alternator to a safe level.
> >
> > Keep in mind that the B&C "regulator" is an alternator
> > control system. It includes ov protection and low voltage warning.
> > This works out to three gizmos in one box for $75/gizmo. Yeah,
> > if the only task was to regulate the voltage based on some
> > scheme designed to enhance battery life, we could produce such
> > a device for a whole lot less than $225.
>
>And the three-stage regulators are a charge control system. What's in
>a name? OTOH, once you put in the microprocessor you can combine some
>of the functions to reduce parts count.
Yup, there are some really interesting products coming over
the hill. Very capable and good value too. I told
Bill this was coming 10 years ago and encouraged him to have
a replacement product on the back burner for introduction
5 years ago. He has decided to invest IR&D $time$ in other
products.
I suspect that R12 or at latest R13 of the 'Connection will
have to show the LR series regulators from a historical
perspective and recommend some more modern offerings as
products of choice.
Bob . . .
Message 17
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Subaru z-figure |
--> AeroElectric-List message posted by: "Jon Finley" <jon@finleyweb.net>
Hi Hans,
I think I've seen your electrical system schematic (maybe on the FlySoob
list) but can't find it now. Do you have it posted somewhere?
Jon Finley
N90MG Q2 - Subaru EJ-22 DD - 467 Hrs. TT
Apple Valley, Minnesota
http://www.FinleyWeb.net/Q2Subaru
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com] On
> Behalf Of Hans Teijgeler
> Sent: Wednesday, March 16, 2005 2:25 AM
> To: aeroelectric-list@matronics.com
> Subject: RE: AeroElectric-List: Re: Subaru z-figure
>
>
> --> AeroElectric-List message posted by: "Hans Teijgeler"
> --> <hans@jodel.com>
>
> Jon,
>
> Your requirements exactly match mine. Strictly VFR, Subaru
> engine and tough luck for ATC, but as soon as my alternator
> dies the radio will be switched off, no lights, no strobe, no
> tpx, no electric flaps, no electric trim, just the engine to
> feed from two batteries.
>
> I've ended up with a very simple diagram:
>
> Battery A feeds pump A, computer A and the main bus.
> Battery B feeds pump B, computer B and the starter
> One alternator tops off both batteries through some diodes
>
> No crossfeeding, no E-bus, no complexity. I know that I am
> throwing away a lot of flexibility, I know that a triple
> failure might shut me down (alternator, battery A and
> computer B broken = glider), but I can live with that. The
> reduced complexity makes up for that- for me.
>
> Thanks Bob for the preview. The diagram makes a lot of sense
> if you want to keep alive more than the engine alone. Like
> with Jon, it simply is overkill for my requirements.
>
> Hans
>
>
> > -----Oorspronkelijk bericht-----
> > Van: owner-aeroelectric-list-server@matronics.com [mailto:owner-
> > aeroelectric-list-server@matronics.com] Namens Jon Finley
> > Verzonden: dinsdag 15 maart 2005 17:48
> > Aan: aeroelectric-list@matronics.com
> > Onderwerp: RE: AeroElectric-List: Re: Subaru z-figure
> >
> > --> AeroElectric-List message posted by: "Jon Finley"
> > --> <Jon@finleyweb.net>
> >
> >
> > Sort of opportune moment to jump into this thread Ive been
> trying to
> > find the time to compose some intelligent questions about a simple
> > electron- dependent-engine system (Subaru).
> >
> > After studying the Z diagrams (I've not yet studied these
> sneak-peak
> > diagrams), I came up came up with the system posted on my website
> > (http://www.finleyweb.net/default.asp?id=131). This was
> designed and
> > constructed more than a year ago. Since this time Ive
> learned a lot
> > by lurking here and now understand that my system has a number of
> > weaknesses/problems (which probably means that are more
> things that I
> > dont even know about yet).
> >
> > My biggest issue/hurdle is that the relevant Z diagrams seem overly
> > complicated for my simple system. I do not have a highly complex
> > airplane nor do I have a difficult mission profile. While I
> am an IFR
> > pilot, I know that my airplane is strictly VFR. When I detect an
> > electrical problem, everything in the airplane is going to be
> > shutdown. The engine keeps running from the battery and I
> land (within
> > an hour). I dont NEED a radio, transponder, gauges,
> five-hour range,
> > etc... just need the engine to keep running for a bit. I could
> > probably babble on for a long time about this but my point
> (really a
> > request) is that I would really like to see a simple system for a
> > Subaru.
> >
> > Thanks Bob!
> >
> > Jon Finley
> > N90MG Q2 - Subaru EJ-22 DD - 467 Hrs. TT
> > Apple Valley, Minnesota
> > http://www.FinleyWeb.net/Q2Subaru
> >
>
Message 18
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Alternators] |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 12:47 PM 3/20/2005 -0600, you wrote:
>--> AeroElectric-List message posted by: Charlie England
><ceengland@bellsouth.net>
>
>Bob,
>
>This showed up on another list & some would like to see your comments,
>since you are directly involved in certified hardware. I'm pretty sure I
>could write more about the inconsistencies here than he's written about
>the differences, but I'd also like to see your opinion. I'll post back
>to the other list if that's acceptable.
>
>Thanks,
>
>Charlie
>
>Begin quote:
>
> From Pifer's Airmotive, Inc. Pontiac MI
>
> DIFFERENCES BETWEEN AIRCRAFT & AUTO ALTERNATORS USING A FORD BELT DRIVEN 12v
>OR 24v ALTERNATOR FOR A COMPARISON
>
> 1. Although alternators are bi-rotational, aircraft engines turn opposite of
>automotive. This means cooling fans must be canted in the opposite direction.
>Also, pulley and belt size vary due to coming-in speed.
An automotive fan looses only 10 percent or so of its cooling
efficiency when spun the wrong direction. Van used to sell or
recommend an alternator that featured an external cooling
fan. He recommended removing it because it turned "the wrong
direction". Bad idea. The alternator went from a slightly
compromised fan to NO fan.
Modern alternators have bi-directional fans and I now believe
most have brushes mounted right over the slip-ring shaft center
so these alternators can be spun either direction without
concerns.
> 2. The thru bolts are of a higher tensile strength utilizing an
>anti-rotation device in the form of a lock tab. The rectifier assembly has
>a heavy duty
>diode with higher voltage and amp. capacity. Also, one excites at 90 PIV (Peak
>Inverse Voltage) and the other at 150 PIV. Radio suppression is designed for
>108 frequencies and up which is the VHF and 108 and down which is FM band.
The gentleman may indeed be looking at the specifications
for some "certified" alternator. Further, the datasheet may
be some revision printed in 1975 . . . It's difficult to know.
Radio noise from alternators is not a big issue at VHF
comm and nav frequencies. ADF and LORAN are the vulnerable
systems. Many (if not all) of the alternators I've seen torn
down over the last 5 years have hi-quality filters built in.
AM radio receivers are the vulnerable system in cars and it's
not difficult to include such filtering in the alternator's
basic design. I doubt anyone even makes a diode that won't run
at 200 volts plus. This used to be a big deal but it's so easy
to craft a diode that nobody worries much about tailoring one
for a low voltage application. Thru bolts are NOT an issue. The
automotive conversions have run quite well by the thousands
of installations over a decade.
Certified aircraft alternators crap with regularity. The
vast majority of B&C alternators sold over the past 15 years
are still running as original installation parts.
> 3. The brushes have a higher graphite content and they utilize a tin plate
>on the brush leads to prevent corrosion.
Bull hocky. Corroded brush leads are the very LEAST of one's
concerns for brush life . . . don't know about the "graphite content"
and can't imagine why it's an issue on slip rings.
> 4. The stator is of the Delta wind rather than the Y" wind and it does not
>utilize the stator terminal. The aircraft unit also carries H" insulation
>which is capable of 200 degrees centigrade temperatures. It also is rated at
>60 amp. instead of 55.
Also bull hockey . . . one can wind the stator any way they
wish to take advantage of some feature that gives is preference
over another. I've read the sand-sifting offered by several
folks on this subject but there are alternators wound both
ways that perform just fine. Some older airplanes use the center
tap "stator" terminal to drive an alternator failure warning system
but this is super-antiquated. With a low voltage warning lamp, you
can deduce everything the pilot NEEDS to know about altenrator
performance whether the thing is Y or Delta wound.
> 5. The rotor has a shorter shaft and a smaller thread size. Because of the
>opposite rotation it is wound in the opposite direction.
Yes, the nuts retaining the pulley on an ND alternator running
in an airplane are put on with an impact wrench. Sometimes
the pulley is keyed to a flange on the shaft which makes thread
direction irrelevant for pulley retention. Alternator shaft torques
are so low that clamp up forces on a properly installed nut
totally negate any sensitivity to direction of threads.
>It also uses "H insulation and Havel varnish.
Everybody used class "H" insulation. An automotive alternator is
more likely to run at temperature limits than anything on an airplane.
Cars don't get the benefits of lower ambient temps and 100+ MPH
ram air if needed.
> 6. The front and rear housings are the same as automotive.
>
> With this brief description, I hope I have enlightened you on the
>differences between aircraft and automotive alternators. Using automotive
>units in an
>aircraft creates a potential safety hazard as well as a short alternator life
>and unreliability.
My sense is that the data being offered is outdated and features
offered as uniquely "aircraft" because the product has been spec'd
onto somebody's type certificate are overblown or irrelevant to the
application.
Given the DEMONSTRATED service life of modern automotive alternators
on OBAM aircraft and exemplar performance in automobiles, I venture
to say that one wouldn't want to put an "aircraft alternator" on a
car. They're expensive, fewer folks stock them, even fewer folks have
parts for them and they don't last as long.
I'd opt for an ND alternator modified to run external regulator
for ANY belt driven certified alternator any day.
Bob . . .
Message 19
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Tap into antenna coax? |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
Don't know how long Jim's had his butt-ugly hand held antenna adapter
article posted. My own version is at:
http://aeroelectric.com/articles/commtap/commtap.html
HOWEVER, the top paragraph of my article cites the preferred way
of breaking into the feedline for your comm antenna . . . put a
male/female junction in the feedline with some excess coiled under
a seat or behind a velcro'ed upholstery panel. The coax "T" will not
work and puts one or both radio's receivers at risk for damage by
the other radio's transmitter.
Bob . . .
At 10:16 AM 3/20/2005 -0600, you wrote:
>--> AeroElectric-List message posted by: Charlie England
><ceengland@bellsouth.net>
>
>James E. Clark wrote:
>
> >--> AeroElectric-List message posted by: "James E. Clark"
> <james@nextupventures.com>
> >
> >Another option ...
> >
> >King used to make an adapter for their KX99 Handheld that can be used.
> >Basically the mini jack/plug arrangement opens the coax from the panel and
> >closes the connection to the handheld. It is all done in a neat little box
> >and you get a mini->coax pigtail.
> >
> >Don't know if they still sell them or not.
> >
> >James
> >
>
>snipped
>
>You can make one of these for yourself if you're handy with a soldering
>iron. Jim Weir actually described construction in an old Kitplanes article.
>http://www.rst-engr.com/kitplanes/KP0203/KP0203.htm
>The design won't make HAM radio guys or RF engineer types happy, but it
>works fine considering the limited use it will get. If you're really
>worried, put it in a little aluminum box.
>
>Charlie
>
>
>--
>No virus found in this incoming message.
>Checked by AVG Anti-Virus.
>Version: 7.0.308 / Virus Database: 266.7.4 - Release Date: 3/18/2005
>
>
>-- incoming mail is certified Virus Free.
>Checked by AVG Anti-Virus.
>Version: 7.0.308 / Virus Database: 266 - Release Date: 3/18/2005
Bob . . .
--------------------------------------------------------
< Throughout history, poverty is the normal condition >
< of man. Advances which permit this norm to be >
< exceeded -- here and there, now and then -- are the >
< work of an extremely small minority, frequently >
< despised, often condemned, and almost always opposed >
< by all right-thinking people. Whenever this tiny >
< minority is kept from creating, or (as sometimes >
< happens) is driven out of a society, the people >
< then slip back into abject poverty. >
< >
< This is known as "bad luck". >
< -Lazarus Long- >
<------------------------------------------------------>
http://www.aeroelectric.com
Message 20
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Crowbar OV Protection |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 08:27 AM 3/19/2005 -0500, you wrote:
>--> AeroElectric-List message posted by: "Mike Lehman" <lehmans@sympatico.ca>
>
>My question refers to the VR-166 Ford type voltage regulator with an
>alternator B+ to regulator terminal 'A' connection supplying alternator
>field current. When the crowbar protection reduces VR terminal 'S' to under
>2 volts, is the field current supply via terminal 'A' always interrupted? I
>presume that the answer depends on the failure mode of the VR-166 that
>caused the crowbar to 'fire' in the first place.
>
>In other words, with the old mechanical VR-166, I have confidence that the
>crowbar protection is adequate. Substituting an electronic VR-166 (with the
>B+ to terminal 'A' wire, not with terminal 'A' and 'S' jumpered per Bob's
>diagrams) seems to create the equivalent of an alternator with an internal
>voltage regulator.
How so? Trace the connection between B-lead and field supply if
the master switch or field supply breaker are open?
>Hopefully, alternator field current via VR termimal 'A', with terminal 'S'
>de-energized, is a low probability VR-166 failure mode? Anyone really know
>???
Some if not most solid state clones of the original Ford
electro-mechanical regulator are form, fit and function
replacements. The original electro-mechanical regulator had
only a voltage regulator 'relay' and could have been made
to function without a field relay. See
http://www.aeroelectric.com/Pictures/Ford_EM_Reg.jpg
http://www.aeroelectric.com/Pictures/Ford_EM_Reg_Field_Relay.jpg
http://www.aeroelectric.com/Pictures/Ford_EM_Reg_Volage_Relay.jpg
The field relay monitored voltage at the stator tap of a
"Y" wound alternator. An alternator fail indicator lamp
was wired across the open contacts of the field relay.
The 100 mA or so of lamp current would excite the alternator
enough so that the alternator would excite and bring the
stator center tap up to about 1/2 bus voltage. "S" on
the regulator was the field relay coil connection and
went to "S" on the alternator stator winding.
Cessna simply used the "S" terminal on the regulator
as a field control and turned the relay on/off with
1/2 of the split rocker. Later, the OV protection
went into this lead.
When the solid state clones came out, there was
and intense desire to eliminate all forms of relay
and this is an exemplar product:
http://www.aeroelectric.com/Pictures/Ford_SS_Reg.jpg
http://www.aeroelectric.com/Pictures/Ford_SS_Reg_open.jpg
Look ma! No relays.
Problem was that some "forward looking" designs used
the old "S" terminal for bus voltage sensing instead
of field CONTROL . . . field source came in through "A"
like always. However, when dropping voltage on "S", instead
of opening a relay that REALLY shut the alternator
off, the regulator instead senses low bus voltage and
full-fields the alternator. Tried one of these
regulators to test the alternator system in a Cessna
and was surprised to find that shutting off the master
switch did NOT kill the alternator but in fact, produced
a design induced OV runaway.
Hence, all my drawings that utilize the generic Ford
regulator tie "A" and "S" together and run those off
to the bus via the master switch and alternator field
breaker. No problems will be encountered with this
wiring philosophy irrespective of the regulator you
find laying around.
Getting back to your original question: When wired as
shown in Z-23, as soon as the SCR in the ov module
fires, field supply to the alternator chokes off at
2 volts or less and the alternator begins to go to
sleep even before the circuit breaker trips. When it
does trip, the dragon fires are completely dead.
Bob . . .
Message 21
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Re: Points for discussion OVP//more |
--> AeroElectric-List message posted by: "Dan O'Brien" <limadelta@gmail.com>
>>this [Lancair's endorsement of the aeroelectric connection approach]
>> is clearly an endorsement from a pretty big player in the experimental
>>category.
> Yes, this is VERY dated info but not particularly relevant.
Not RELEVANT? Ever heard of Bayes theorem? It's a basic fundamental
in probablility theory, which is fundamental to every other scientific
discipline. It's also a basic building block of rational
decision-making. If a customer believes a) Lancair knows something
the customer doesn't know, and b) Lancair is not randomly pitching
darts in drawing their endorsment, then Baye's theorem implies the
endorsement is "relevant" to the customer. This is nothing more than
probability 101.
Get it?
And by the way, your political analogies to my last two posts were,
well, political analogies that were not particularly relevant.
Message 22
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Crowbar OV Protection |
--> AeroElectric-List message posted by: "Jerry Grimmonpre" <jerry@mc.net>
Bob, Paul, listers...
You are reading from the keyboard of a complete novice, sometimes I don't
know my + from my -- butt (pun) manage to get by with the dirt simple stuff.
With that said and trying to follow more experienced minds, in this debate,
I would like to run this idea by the jury.
I understand the drawing AND testing of circuits are now done with computer
programs. Isn't it, therefore, possible to do this OVP design work and
testing like that? If that can be done, how about a step further ... slow
down the simulated progress of the circuit so all those electrons can be
both, tracked and timed as to their behavior. Design out the problems and
build it. What could be simpler? Tell us all this can be done and for the
jury to standby. My 2 cents is standing by.
Appreciate all the talent you pros display in this debate and with best
regards ...
Jerry Grimmonpre
Message 23
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | RE: LOCATION OF WX 500 ANTENNA |
--> AeroElectric-List message posted by: CHAD FELDPOUCH <1pouch@sbcglobal.net>
Can anyone tell me if it will matter much if I mount a WX 500 antenna within 8
inches from an Stec pitch trim servo ? It will also be about 18 to 20 inches from
the landing gear power pack , battery and a couple solinoids . I know what
the install manual says, but this is about the only good location I have and
there would not be a place in the whole plane to meet the requirements of the
install manual . Will this work ? Also can I mount a GDL 49 , WX 500 processor
and an HSI remote gyro within 2 inches of each other and within 6 to 8 inches
from the battery and the landing gear power pack ?
Thanks,
Chad..
CHAD FELDPOUCH
FELDPOUCH AVIATION
PHONE: (618) 267-8035
FAX: (618) 283-7285
EMAIL: 1pouch@sbcglobal.net
Message 24
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Crowbar OV Protection |
--> AeroElectric-List message posted by: "Matt Prather" <mprather@spro.net>
Hi Jerry,
What you propose is a not a bad idea. Electrical Engineers use
circuit simulation software all of the time. Usually, they are used
for circuits with far more components. For an application like
this, there are limitations in the capabilities of the software,
unfortunately.
In this case, probably the biggest limitation is that simulations
depend on accurate models of the circuits they simulate. The way
the sim software that I am aware of works is that the engineer has
to draw out what the circuit looks like in terms of conductors,
resistors, capacitors, inductors, transistors, transformers, and
diodes. The key to making the software work is identifying what
components actually exist, and where. Sometimes that's a big
challenge, becuase it may be difficult to know just how much of each
fundamental electromagnetic principle is happening.
For instance, it's often difficult to model noise propagation. Let's
say two parallel conductors sit somewhat adjacent. How much do
current transients on one conductor affect the adjacent wire? That may
be difficult to predict.
Then, to make use of the model, the user has to figure out what
kind of electrical signals should be used to stimulate the circuit.
It's only slightly like a CSI simulation. :)
Even though the alternator/regulator bus circuit might seem like it has
a bunch of components, it should be rather simple model. Consider that
sims are built for circuits that have literally billions of transistors.
None the less, what you suggest is worth probably worth trying. Almost
always, something interesting is learned from attempting to build a
detailed circuit model. Who wants to break out some SPICE? I've
been away from it for so long it would take me a while.
Regards,
Matt-
VE N34RD, C150 N714BK
> --> AeroElectric-List message posted by: "Jerry Grimmonpre"
> <jerry@mc.net>
>
> Bob, Paul, listers...
> You are reading from the keyboard of a complete novice, sometimes I
> don't know my + from my -- butt (pun) manage to get by with the dirt
> simple stuff. With that said and trying to follow more experienced
> minds, in this debate, I would like to run this idea by the jury.
>
> I understand the drawing AND testing of circuits are now done with
> computer programs. Isn't it, therefore, possible to do this OVP design
> work and testing like that? If that can be done, how about a step
> further ... slow down the simulated progress of the circuit so all
> those electrons can be both, tracked and timed as to their behavior.
> Design out the problems and build it. What could be simpler? Tell us
> all this can be done and for the jury to standby. My 2 cents is
> standing by.
> Appreciate all the talent you pros display in this debate and with best
> regards ...
> Jerry Grimmonpre
>
>
Message 25
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | RE: LOCATION OF WX 500 ANTENNA |
--> AeroElectric-List message posted by: "Jim Stone" <jsto1@tampabay.rr.com>
What kind of plane are you working on?
Jim Stone
Jabiru J450
Clearwater FL.
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of CHAD
FELDPOUCH
Subject: AeroElectric-List: RE: LOCATION OF WX 500 ANTENNA
--> AeroElectric-List message posted by: CHAD FELDPOUCH
--> <1pouch@sbcglobal.net>
Can anyone tell me if it will matter much if I mount a WX 500 antenna
within 8 inches from an Stec pitch trim servo ? It will also be about 18
to 20 inches from the landing gear power pack , battery and a couple
solinoids . I know what the install manual says, but this is about the
only good location I have and there would not be a place in the whole
plane to meet the requirements of the install manual . Will this work ?
Also can I mount a GDL 49 , WX 500 processor and an HSI remote gyro
within 2 inches of each other and within 6 to 8 inches from the battery
and the landing gear power pack ?
Thanks,
Chad..
CHAD FELDPOUCH
FELDPOUCH AVIATION
PHONE: (618) 267-8035
FAX: (618) 283-7285
EMAIL: 1pouch@sbcglobal.net
=
=
Message 26
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: relevancy redux |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 09:40 PM 3/20/2005 -0500, you wrote:
>--> AeroElectric-List message posted by: "Dan O'Brien" <limadelta@gmail.com>
>
> >>this [Lancair's endorsement of the aeroelectric connection approach]
> >> is clearly an endorsement from a pretty big player in the experimental
> >>category.
>
> > Yes, this is VERY dated info but not particularly relevant.
>
>Not RELEVANT? Ever heard of Bayes theorem? It's a basic fundamental
>in probablility theory, which is fundamental to every other scientific
>discipline. It's also a basic building block of rational
>decision-making. If a customer believes a) Lancair knows something
>the customer doesn't know, and b) Lancair is not randomly pitching
>darts in drawing their endorsment, then Baye's theorem implies the
>endorsement is "relevant" to the customer. This is nothing more than
>probability 101.
>
>Get it?
>
>And by the way, your political analogies to my last two posts were,
>well, political analogies that were not particularly relevant.
Hmmm . . . I'll have to ponder that a bit. Permit me to clarify
my perceptions of "relevancy" and use of the term:
There have been many purveyors of products, information and
services who have achieved some level of popular or even
critically reviewed acclaim for their efforts. I'm personally
extra-critical of acclaim embedded in the work of others.
Particularly when it's very outdated and when there has
been essentially zero participation by Lancair on this
list or through any other communication with me. Not
that I'm bad-mouthing acclaim from folks who are leaders
in their chosen skills . . . but please consider this
example.
There's a manufacturer of an up-and-coming
glass cockpit system who's popularity and loyal consumer
base might reasonably expect HIS evaluation of MY
work to be "relevant" in the scientific community.
None-the-less, we had a little tte--tte with the
gentleman a few months ago where degrees of both modest
acclaim and energetic berating could be had in the short
span of 5-6 email exchanges.
See:
http://aeroelectric.com/articles/richter/richter.html
So what relevancy should I place on either acclaim or
berating from this particular source even though
his customers seem to find good value in his products
and choose to believe he walks on water?
An contrary extreme might be illustrated
by this hypothesis: Suppose someone like Saddam Hussein
says the "Connection is the best electrical system book
out there" and because his words are faithfully repeated
through many channels I suddenly get orders for thousands
of books. While it might be good for the bank account
I cannot imagine a worse endorsement.
If you're selling high dollar sneakers, then acclaim
from anyone having name recognition seems to boost
the sales of those shoes whether or not the individual
making the endorsement wears or even likes the product.
I'm VERY pleased for the positive support from a
company like Lancair. I'd be equally pleased to have
positive support from Blue Mountain. But in ANY and
ALL cases, relevancy of the support has more to do with
mutual understanding of the topic of interest and
less to do with how many books I've sold, how many
glass screens he's sold, how well their airplanes
fly, or how many acolytes any of us have acquired.
In the case of both Lancair and Blue Mountain, I
can attest to very little or no mutual understanding
of what transpires here on the List or in my published
works.
This is how I evaluate relevancy of acclaim as a scientist,
engineer and teacher. Others are certainly free to place their
own boundaries on the meaning of the term. But in any
instance my friend, please know that I wasn't whacking
on you.
Bob . . .
Message 27
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Crowbar OV Protection |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
At 09:39 PM 3/20/2005 -0600, you wrote:
>--> AeroElectric-List message posted by: "Jerry Grimmonpre" <jerry@mc.net>
>
>Bob, Paul, listers...
>You are reading from the keyboard of a complete novice, sometimes I don't
>know my + from my -- butt (pun) manage to get by with the dirt simple stuff.
>With that said and trying to follow more experienced minds, in this debate,
>I would like to run this idea by the jury.
>
>I understand the drawing AND testing of circuits are now done with computer
>programs. Isn't it, therefore, possible to do this OVP design work and
>testing like that? If that can be done, how about a step further ... slow
>down the simulated progress of the circuit so all those electrons can be
>both, tracked and timed as to their behavior. Design out the problems and
>build it. What could be simpler? Tell us all this can be done and for the
>jury to standby. My 2 cents is standing by.
>Appreciate all the talent you pros display in this debate and with best
>regards ...
Yes, all this stuff can be and is indeed accurately simulated. In fact,
the next installment to the White Paper will take advantage of some
computing as an aid to the analysis. But before the computer can
do good work, the models have to be accurately entered for each
component. Things under discussion now about the effects of internal
impedance, wiring resistance, battery behavior, etc. must all be
deduced and properly modeled or the simulation will be at least suspect
and possibly useless (garbage in, garbage out).
I find herding electrons on the bench and recording results with
'scope and camera is a better way to share simple-ideas with
a range of individuals having many levels of understanding. It's also
useful to do the touchy-feely thing with the hardware and
tools as opposed to running any simulation no matter how
well crafted. After years of designing and building products
I'm still surprised at the appearance, shape and feel of
a new etched circuit board or a machined part when I pick it
up for the first time. In spite of having stared at its
representation on the screen for hours, picking up the real
part for the first time is both a revelation and decided buzz.
The real pleasure of holding the elegant solution in your
hand or watching it do the job for a satisfied customer
is the acme of understanding and design. Simulation can
be a useful tool but for me at least will always be a tiny
part of the path between simple-ideas and satisfied customers.
Bob . . .
Message 28
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
--> AeroElectric-List message posted by: "Paul Messinger" <paulm@olypen.com>
I was startled, surprised, astonished, and disappointed by what starts out
like a professional engineering report and rapidly changes into very non
engineering list of strange assumptions that are not supported by the facts
as presented by the manufacturer's data sheets.
Further the included, technically flawed, analysis fails to support the use
of any combination of parts which any GOOD analysis must do if the design is
made available as a do it your self design where any part combination is
likely to be used.
Sorry this is so long but I am only doing to this report what Bob has often
done to other reports he did not care for.
My entire career in engineering was marked with respect for and by my
associates. When one made a report of his or her test results, the rest of
us would consider the results and ask questions. If one of us wanted to
duplicate the results (I cannot recall when this was ever done however), we
would already have the details as that was always a part of the discussion.
Perhaps more important, any test results would always include an analysis of
why this result compared to the part specifications and therefore what one
could reasonably expect any random selection of parts to produce. This is
always required to validate the design for production. Never was a single
test used to validate the design. It was always supported with a worst case
analysis to validate the design for production.
I tested the OVP design dozens of times using different batteries and using
3 different CB designs from 2 manufacturers based on what parts were being
used in general aviation aircraft and commonly available to builders from
common sources like Wicks and Aircraft Spruce. My test setup was a mock up
simulation of a basic aircraft electrical system including parts, wire
sizes, and lengths. From a good battery thru common contactors (3 different
types and 2 manufacturers also normally available from AC etc) and a
operating alternator (ac motor driven) and last but not least the OVP as
described in Aeroelectric connection (this was and is the so called load
dump test series that was mostly conducted in the spring of 2004. The
specific CB used in this subject test is NOT available from these common
sources but is a good part for aircraft usage however)
The so called load dump testing we did last year rapidly expanded to EVERY
part of a basic electrical system Thus it included the OVP crowbar which is
the subject of this specific discussion
In fact there is not a single part of the subject test that represents
neither what I tested nor what might be found in any real aircraft (with the
exception of the CB). What I tested (and its detailed setup) would have been
provided to Bob (if only he had asked). This at least could have made his
test an apple to apple test for a reasonable comparison.
However in this case there are no usable conclusions other that there is
some current pulse, of some amplitude, and some trip time and neither of us
have defined the max/min parameters. I only wanted to define what was inside
the realistic range to show how ridiculous the crowbar approach was and Bob
apparently wanted to show how good it was and appeared to have set the test
up to produce a lower current pulse and perhaps a shorter time to open the
CB. Its also apparent he wanted to disprove my test results (which I take as
a personal insult to my professional career).
Bob made a test that is not like any real aircraft wiring etc and made
conclusions that were not consistent with the component's data sheets. In
fact a glance at the CB data sheet should have raised a red flag that
something was wrong as the test results of 15 ms to trip is outside the
range of 46 ms to 800 ms. at 1000% of rated current (at 25 deg C). True
the test was at nearly 3000% of rating and the data sheet only went to
1000%. However looking at the data sheet it's hard to get 15 ms as
reasonable for a typical CB. While it's possible the part was in spec it's
clearly NOT typical!
My testing quickly discovered that the very first trip in the morning at 15
C was nearly double the following trips made several minutes later. I would
guess that Bob's test results were after several dry runs to verify the
measuring equipment etc. This would have internally heated the CB and
produced, as I found out, 1/2 the cold trip time that is what one could
expect in normal aircraft operation. The temperature sensitivity is defined
on the data sheet which seems to not have been referenced. Again as the trip
time is well out of specification for any but the fastest in spec CB. Surely
one could not expect a 800ms part to trip in 15 ms even considering the
overload. As trip time is not linear with increasing loads (from the data
sheet again). If the XB was heated from recent testing and at the fast end
of the specification tolerance I can see 15ms as possible. I found that I
needed to wait nearly one hour to get valid cold trip times (and it was not
unusual to have trip times cold of over 100ms)..
In any event I have no reason to question Bob's test results. Bob has not
offered me the same courtesy which is unfortunate. (6 other experienced
engineers have and 2 actually inspected the setup and witnessed the testing,
all concurred with my test setup and results 400 amps and 50 ms or longer
time to trip)
Bob then goes on with "out of the thin air conclusions" :-) that are not
based on any real facts and in fact the available data (again from various
data sheets) do not support the conclusions.
For example:
From the report:
". Battery delta E for 135A load is about 2.4 volts for an internal
impedance of about 17 milliohms.
About what one would expect from a two year old battery that started out in
the 8 to 10 milliohm."
The Panasonic data sheet says approximately 12 milliohm. Approximately is
hardly an engineering term but it's also not 8-10 as Bob suggests for a new
battery.
My testing was with 2 parallel PC-625 batteries 4 years old and they have
been load tested to be like new. Each has a specified internal resistance of
7 milliohms and 2 in parallel is 3.5 milliohms Nearly 5 times lower. That
alone is a major reason why my test current was 3 times higher.
As for the greater duration of the event 15ms vs. 50 ms I suggest its likely
my parts were closed to nominal in the range of 50-500ms to start with for
the 7277 CB. If this was not the only variable it could be a simple
explanation for most of the different test results.
With the small size the OVP has a nice home taped right on the side of the
CB so there is essentially no lead resistance to deal with. I can see no
reason for the wire lengths in Bob's report.
Why 2 batteries? I was only using the design that Bob suggests for an
electrically dependent aircraft in normal operation with 2 batteries
connected together so both get charged from the one alternator. No attempt
to load the test other than to use what I feel are far better batteries but
that is another issue.
Going on we find a violation of ohms law :-)
From the report:
". Wiring drops during the crowbar event were about 8.4 volts for a loop
resistance on the order of 62 milliohms.
. Energy dissipated in the SCR during the crowbar event was E*A/t or 2.0 x
135 x 0.015 or 4 watt seconds.
Analysis:
. This experiment illustrates the ways that resistance of individual
features can stack on top of each other. 2-feet of 20AWG wire used to wire
the experiment contributes only 20 milliohms of the 62 milliohm total we
observed. The experiment has 6 crimped terminals and 6 bolted joints.
. Further, the circuit breaker when new is rated for a maximum voltage drop
of 0.35 volts at 5A or 7 milliohms
When I do the math I get 70 NOT 7 milliohms on the last line (for the CB)
which conflicts with the first line of 62 milliohms total loop resistance.
From this and my earlier comments the entire technical analysis is clearly
faulty.
There is much more I could point out with regard to faulty assumptions; but
assumption is not a term I ever allowed my engineers to make. We use real
data and cannot afford to make guesses etc. Further, and much more
important, we never allowed the use of a 'sample of one' lab test as more
than a proof of concept. Here the battery used is no where typical of what
should be used, nor are ANY of the conclusions regarding the trip times
given the wide range in the manufacturers data sheets that indicate trip
times 10-20 times longer are possible. 15 ms vs. 400+ ms is not
insignificant. Based on the SCR data sheet I expect that the mild overload
as tested here would be a gross overload with a worst case long time to
trip. 400 ms is a very long time for a 25 amp device.
If wiring resistance, CB trip times, etc are critical then this needs to be
made clear so any builder is alerted to such constraints. I know of no such
warnings.
Consider the following data from the manufacturer's data sheet on 3 of the
more popular CB that are commonly available and I tested.
I used is a Klixon 7277 vs. the Klaxon 7274 which is commonly available and
has a max voltage drop of 0.25 v vs. 0.35 v for the 7274
At 1000% the time to open is 0.028-0.550 seconds for the 7277.
At 1000% the time to open is 0.046-0.800 milliseconds for the 7274
(Both specified for aircraft use by Klaxon). Both have similar but
significantly different specifications.
The Klixon 7271 has a specified trip time at 1000% is 1.4 seconds.
The W23 is listed at 0.03 ohms +/-30%
The Trip time at 1000% is 0.25-0.6 seconds
In conclusion Bob seems to have missed my point entirely. I demonstrated
that the crowbar could produce currents of as much as 400 amps and time to
open of 50 ms (or much more). This is entirely unnecessary with a different
approach to OVP design. Even adding a 1/4 ohm resistor in the OVP module
cuts the current down to 50 amps or less which still pops the CB nearly as
fast. After all, 50 amps is 1000% overload and the maximum load specified
where the time to open is defined.
My issue is that it is not important if the current is 100 amps or 400 amps,
neither is needed for a fast trip, and is an overkill with questionable side
affects (in a upcoming post, yes there are many more issues to consider)
The parts I have selected for the 21 st century system shut down in a
millisecond at 200% of rated current or what ever limit I program into it.
No large current pulses (even 50 amps is large for a 5 amp circuit) and it
shuts down many times faster. Smaller, lighter, more reliable, and meets
much higher test standards than required in DO-160 plus its much lower cost.
I simply do not understand the massive resistance to make an improvement
(even the addition of 1/4 ohm is resisted).
Paul Messinger
Message 29
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: White Paper on Crowbar OV Protection |
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <b.nuckolls@cox.net>
>
>Actually, my question was intended to be a lot more specific than that.
>I think Paul Messinger raised concerns about a load dump damaging
>regulators when the contacter is opened on the "B" lead, because the
>crowbar short drives the alternator to full output before the contacter
>opens.
>
>In the whitepaper, Bob said
>"If one uses a crowbar OV module in combination with an internally
>regulated alternator, field supply to the alternator is choked off at
>the 2 volt level as soon as the SCR fires . . . the alternator is
>already starved for field current long before the breaker opens."
>
>My question is: "Is that really true?" I can see how that would be the
>case for an externally regulated alternator, but I am not convinced that
>dropping the field voltage to 2 volts would do anything to reduce the
>output from an internally regualted alternator - which is the original
>problem.
Bad on me. That's a typo. The alternator under discussion in
that paragraph is EXTERNALLY regulated. This will be fixed in
rev C.
>I have no doubt the crowbar would protect the rest of the devices on the
>bus, but the concern is what could it do to the regulator if you open
>the B lead when the alternator is producing maximum output.
>
>I have some similar concerns about the system I will have on my Rotax,
>as the suggested design for that also has a contacter on the output
>lead, although (correct me if I'm wrong) I don't think the PM
>alternators have the same problem with load dump because they don't
>control the magnetic field.
All alternators will experience some degree of "load dump"
phenomenon. It's a function of regulator/alternator dynamics
for rapidly changing loads . . . particularly large ones
that disappear suddenly. It would really be nice to have
access to a Rotax alternator on a drive stand to explore
it's true nature but I don't see that happening soon.
Bob . . .
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|