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darinh
Joined: 20 Apr 2006 Posts: 327 Location: Utah
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Posted: Fri Nov 16, 2007 5:46 pm Post subject: Power Diagram for Review |
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Guys,
I have had this post on the Aeroelectric list with no bites, so I thought I would ask it to you guys. I need some of you electrical geniuses to review my diagram and critique it and let me know if it will work or what needs to change. Here is my setup for background:
Rotax 914 with internal (small alternator) and external 40 amp alternator. My plan is to have the 40A be the primary and the 18A (internal) be a backup on a switch. Other than that it should be a standard Kitfox power system. The diagram shows a "Generic Ford" regulator for the primary alternator but in reality, my alternator has an built in regulator. The Rotax regulator will be connected to the backup.
Please let me know what needs to change as I am covering the fuse on Monday and I would like to do the electrical system next.
Do not archive
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Rotax 914 Modified.pdf |
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135.4 KB |
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402 Time(s) |
_________________ Darin Hawkes
Series 7
914 Turbo
Kaysville, Utah |
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Fox5flyer Guest
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Posted: Fri Nov 16, 2007 6:53 pm Post subject: Power Diagram for Review |
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I wish I could help you out Darin, but even though I managed to muddle
through my electrical system one wire at a time, this isn't my strong area.
I'm surprised that nobody responded to your request on the Aeroelectric List
because they generally jump right on to things like this. Bob himself
usually is a great help, but he's on the road a lot and he might have been
gone during this time. If you don't find the answers you need here, why
don't you try Aeroelectric again? There are a lot of aviation electrical
gurus on that list, probably more than you would find anywhere else in one
spot. This is something you need to ensure you get right (smoke test)
before covering.
Great job on the schematic. Very professional and easy to read.
Good luck,
Deke Morisse
S5, NE Michigan
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darinh
Joined: 20 Apr 2006 Posts: 327 Location: Utah
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Posted: Fri Nov 16, 2007 8:48 pm Post subject: Re: Power Diagram for Review |
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Deke,
To tell you the truth, I was very surprised I didn't get any replies either on the Aeroelectric list. And I agree, I need to get this part right but covering shouldn't affect this part of the process as I have made the boot cowl removable to access all the wiring and fabric doesn't cover this area. Thanks for the comments on the diagram, but I can't take complete credit because I simply used a couple of Bob's diagrams to make it using Autocad.
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_________________ Darin Hawkes
Series 7
914 Turbo
Kaysville, Utah |
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lcfitt(at)sbcglobal.net Guest
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Posted: Fri Nov 16, 2007 10:33 pm Post subject: Power Diagram for Review |
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Darin, It's been a while, but as I recall, the Rotax voltage regulator,
doesn't like to be without a load. It seems I read somewhere that if you
turn it off - no load - you can fry the regulator. Maybe someone else can
clarify this. You might want to put a small battery, a resister or a light
bulb somewhere in the circuit when the aux (small) generator is off line to
provide a small load. Also, I notice you have an overvoltage protection
module in the small generator circuit. I doubt you need it as the unit is a
simple permanent magnet generator rather than an alternator and run away
voltage is not an issue. At least this is the way I understand it. Bob was
a Kitfox list contributor when I was building and he influenced my circuit
design as well.
Lowell
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KITFOXZ(at)aol.com Guest
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Posted: Sat Nov 17, 2007 5:07 am Post subject: Power Diagram for Review |
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In a message dated 11/16/2007 8:50:03 P.M. Eastern Standard Time, gerns25(at)netscape.net writes:
Quote: | Guys,
I have had this post on the Aeroelectric list with no bites, so I thought I would ask it to you guys. I need some of you electrical geniuses to review my diagram and critique it and let me know if it will work or what needs to change. Here is my setup for background:
Rotax 914 with internal (small alternator) and external 40 amp alternator. My plan is to have the 40A be the primary and the 18A (internal) be a backup on a switch. Other than that it should be a standard Kitfox power system. The diagram shows a "Generic Ford" regulator for the primary alternator but in reality, my alternator has an built in regulator. The Rotax regulator will be connected to the backup.
Please let me know what needs to change as I am covering the fuse on Monday and I would like to do the electrical system next.
Do not archive
--------
Darin Hawkes
Series 7 (under Construction)
914 Turbo
Ogden, Utah
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Darin,
Very orderly, nice looking schematic! I see that you have a wire running from the load side of your battery contactor to the supply side of your starter contactor labeled both as a "4AWG" wire and as a "16AWG fuselink"??? I am sure you just left out a tie point between them to illustrate the junction of the two. I want to hear your arguments as to why you don't just run a 4AWG wire from the battery side of your battery contactor to the supply side of your starter contactor and then connect your "current limiter" "note 10" directly to the load side of your battery contactor? My concern is unnecessary voltage drop across the battery contactor contacts during cranking. The two contactors should be located side by side ideally anyway with a short 4AWG jumper in between them or even a brass/copper strap to "join" them as a single assembly.
I also agree with Lowell that the Rotax regulator needs a load on it at all times to stabilize it. A small 1/2 amp load should be plenty. A rewire of the S704-1 relay should do the trick with a resistor to ground. from the N.O. contact.
Everyone always dreads the electrical/electronic phase of construction but, I think you are just beginning one of the most fun and rewarding parts of building!
Enjoy,
John P. Marzluf "John Z"
Columbus, Ohio
Series V Outback (still out back in the garage)
Do Not Archive
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KITFOXZ(at)aol.com Guest
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Posted: Sat Nov 17, 2007 5:18 am Post subject: Power Diagram for Review |
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Darin,
Oops, forgot! Also I don't like the prospect of the battery contactor failing in flight and preventing you from restarting the engine if needed. Did I miss seeing your starter switch configuration?
John P. Marzluf "John Z"
Columbus, Ohio
Series V Outback (still out back in the garage)
Do Not Archive
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Guy Buchanan
Joined: 16 Jul 2006 Posts: 1204 Location: Ramona, CA
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Posted: Sat Nov 17, 2007 6:37 am Post subject: Power Diagram for Review |
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At 10:32 PM 11/16/2007, you wrote:
Quote: | Also, I notice you have an overvoltage protection module in the
small generator circuit. I doubt you need it as the unit is a
simple permanent magnet generator rather than an alternator and run
away voltage is not an issue.
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Darin,
I'll do more review later today, but I can believe that the
output of the voltage regulator can most definitely "run-away" as
mine does so every now and then. (It lets me know the OPM is
working!) I don't know why but I suspect a failing regulator. (Please
note I'm running a 582, but though it has different parts, I think
the operation is the same: PM alternator and 3-phase regulator.)
Guy Buchanan
San Diego, CA
K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.
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_________________ Guy Buchanan
Deceased K-IV 1200
A glider pilot too. |
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Float Flyr
Joined: 19 Jul 2006 Posts: 2704 Location: Campbellton, Newfoundland
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Posted: Sat Nov 17, 2007 6:38 am Post subject: Power Diagram for Review |
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I decided to have a look at this this morning. I do have a couple of
questions.
The OV (over voltage) module on the new alternator will cause the field coil
to ground out thereby popping the field current through the 5A breaker.
Generally these things are wired in such a way to turn on an OV light and
open the breaker. I didn't see any B+ to that OV module to power a light.
In the noisy condition of a cockpit I would think the OV light would be
rather important. It is so easy to miss the breaker popping.
Are you planning on installing two load meters or a double gang switch to
change from one generator to the other as you switch the generators in and
out?
I like the way you have your avionics buss wired to allow avionics override
in the case of a general distribution problem. No one likes the Lucas
effect.... (Lord of the dark)
I notice the dynamo OV module is hot wired through a fuse link to the B+
master terminal. An OV condition would cause the fuse link to blow and then
there is no indication of an OV condition. I think a circuit breaker would
be better in that location. An OV module that would cause an open in the
Aux Alt grounding circuit would not cause the fuse link to blow. The same
sort of OV module should be used on the field circuit of the Alternator.
I think you might be able to simplify the circuit by connecting output of
the Alternator to the NC terminal of the Aux Alt relay. I think it can be
done in such a way the OV will automatically switch the alternator to the
dynamo and give you a warning light (1 of 2). Making the connection that
way will also mean that you will only have one load bridge and one load
meter.
Noel
[quote] --
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_________________ Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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Float Flyr
Joined: 19 Jul 2006 Posts: 2704 Location: Campbellton, Newfoundland
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Posted: Sat Nov 17, 2007 6:51 am Post subject: Power Diagram for Review |
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Just had another look ... By moving the Alternator output form the starter
lug to the NC terminal of the Aux Alt relay you would reduce one load meter
and one load bridge. The Aux Alt off/ on switch should be changed to a
double gang type with the second gang opening the field coil when the Aux
Alt is activated... Not automatic but simpler and less parts.
Noel
[quote] --
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_________________ Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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Float Flyr
Joined: 19 Jul 2006 Posts: 2704 Location: Campbellton, Newfoundland
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Posted: Sat Nov 17, 2007 11:50 am Post subject: Power Diagram for Review |
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Big oops.... I forgot about the reqirement for the Rotax regulator/rectifier
to have a load.
The simple answer to saving the original Aux regulator is to switch the 2 AC
lines coming out of the Rotax internal generator..... No output, no
problems. The way your diagram works the dynamo could go into voltage
runaway.... Only the busses are protected. It would be nice to protect the
dynamo and the regulator too.
I wish I was a lot better with AutoCAD... I'd draw up what I have in mind.
If you switch the AC leads ( both of them) then you won't need switch 1-3.
Come to think of it maybe the best way to go is to put a DPST relay on the
output of the dynamo that really should be OV protected to release when an
OV occurs.
It's a Saturday night and I've had a double martooneyyyyy so I won't be
drawing any thing up until tomorrow.
Noel
[quote] --
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_________________ Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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darinh
Joined: 20 Apr 2006 Posts: 327 Location: Utah
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Posted: Sat Nov 17, 2007 12:17 pm Post subject: Re: Power Diagram for Review |
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Wow,
You guys have done well! Comments from me as to "why" I have done this the way I have will have to wait a day or two as I am prepping the fuse for covering (starting Monday morning) and have just a few items of business to finish before this can happen. Suffice it to say, I don't know why...yes I am ashamed that I don't know electronics but I am a civil engineer, we're not supposed to know about electrons.
I appreciate everyones comments and I will try to research them and make necessary changes before I bug my wise old flying friend about helping me install this (he is an electrical engineer with lots of aircraft wiring experience, just not much time to help me design).
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_________________ Darin Hawkes
Series 7
914 Turbo
Kaysville, Utah |
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