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Dual Alternator Use

 
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markn(at)fuse.net
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PostPosted: Sat Feb 04, 2006 12:30 pm    Post subject: Dual Alternator Use Reply with quote

Being one of Bob's electronic disciples, I was wondering about the use of my
B&C 40amp alternator with the SD-8 together in my GlaStar. Is it OK to use
them both at the same time, yielding an available current output of 48 amps,
or should the SD-8 only be energized when the main alternator is disengaged?
Are there voltage regulation problems having both alternators pumping
electrons into the system busses at slightly different set voltages
(determined by the exact regulator settings)?

Mark Neubauer


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Bruce(at)glasair.org
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PostPosted: Sat Feb 04, 2006 4:27 pm    Post subject: Dual Alternator Use Reply with quote

Mark,

The voltage regulator of the SD-8 is set about 1v less than the normal buss
voltage from your 40 amp main. If the main goes off line the voltage will
sag and the SD-8 will kick in. That means they will both not produce power
at the same time.

Bruce
www.glasair.org


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nuckollsr(at)cox.net
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PostPosted: Sat Feb 04, 2006 5:14 pm    Post subject: Dual Alternator Use Reply with quote

At 09:06 AM 2/4/2006 -0500, you wrote:

Quote:


Being one of Bob's electronic disciples, I was wondering about the use of my
B&C 40amp alternator with the SD-8 together in my GlaStar. Is it OK to use
them both at the same time, yielding an available current output of 48 amps,
or should the SD-8 only be energized when the main alternator is disengaged?
Are there voltage regulation problems having both alternators pumping
electrons into the system busses at slightly different set voltages
(determined by the exact regulator settings)?

Mark Neubauer

Under what circumstances do you think you will need 48 amps?
It's exceedingly difficult to make two alternators . . . especially
different sizes/styles to proportionately share a load. I've
designed special regulators for that purpose, the first back
in the Cessna 303 Crusader days.

Induced quite a bit of little-value-added hardware to the
airplane along with one more black box to go belly up to the
tune of $400/pop

If you really NEED to parallel two alternators, let's talk
some more.

Bob . . .


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nuckollsr(at)cox.net
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PostPosted: Sat Feb 04, 2006 8:30 pm    Post subject: Dual Alternator Use Reply with quote

At 01:01 PM 2/4/2006 -0500, you wrote:

Quote:


Mark,

The voltage regulator of the SD-8 is set about 1v less than the normal buss
voltage from your 40 amp main. If the main goes off line the voltage will
sag and the SD-8 will kick in. That means they will both not produce power
at the same time.

That's the installation rationale for the SD-20 when used with
an SB-1 regulator and wired per Figure Z-12. This philosophy
does not apply to the SD-8 in any of the recommended installations.

Bob . . .


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gmcjetpilot(at)yahoo.com
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PostPosted: Sun Feb 05, 2006 7:05 am    Post subject: Dual Alternator Use Reply with quote

Quote:
From: "Mark Neubauer" <markn(at)fuse.net> Subject: Dual Alternator Use
AeroElectric-List message posted by: "Mark Neubauer" <markn(at)fuse.net>

>Being one of Bob's electronic disciples, I was wondering about the use of my
>B&C 40amp alternator with the SD-8 together in my GlaStar. Is it OK to use
>them both at the same time, yielding an available current output of 48 amps,
>or should the SD-8 only be energized when the main alternator is
>disengaged?
....>
>Are there voltage regulation problems having both alternators pumping
>electrons into the system busses at slightly different set voltages
>(determined by the exact regulator settings)?
>
>Mark Neubauer


Mark:

.....What about running two alternators simultaneously in parallel but isolated.
The 40 amp does the Yeoman's duty, lets call that the (A) system, and the
SD8 back-up runs say 5 amps of other (B) system items. If the SD8 died
you still have the 40 amp. If the SD8 died you would still have system (A).
If you wanted you could manually cross feed the (B) buss and (A) buss in
event one system died (after suitable load shedding, e.g., turning stuff off).
This is the way the Big (jet) Boys do it. Parallel but isolated.

Cons:
....-Wt. (1lb) for small 0.8-1.2 amp/hr back-up (B) system battery
.....-You may be able to use a capacitor vs. a battery for the SD8
http://www.batterymart.com/battery.mv?p=SLA-12V1-3
http://www.batterymart.com/battery.mv?p=SLA-12V0-8


Pros:
....-True redundancy with isolated systems working in parallel
....-Reduced load on the (A) system alternator (B sys not dead wt.)
....-One system will not affect the other (good thing)



THE MARINE SOLUTION
If you MUST have dual sync'ed alternators consider the SD-20 and a
marine voltage regulator. I suggest the SD-20 to keep the dual
alternators of the same type. Marine regulators have been paralleling
dual alternators for decades. They don't cost much more than one so
called advanced regulator. They have all the protection you could
every want: Now having different models of alternators with different
power output potential may pose a challenge, but the marine
companies no doubt have a solution. They may be able to parallel the
SD-8 and L-40 even? You would have to ask. (food for thought only).

http://www.amplepower.com/products/sarv3/index.html
http://www.amplepower.com/products/dual_alt/index.html
http://www.amplepower.com/products/sysnav_ic/index.html
http://www.sterling-power.com/
(select>product>adv alternator reg>pro digital)

I am NOT saying this is the way to go about it, but I'm trying to open
your mind. Marine apps. have been making real rugged, reliable and
redundant DC electrical systems for a long time. If you get into real
Air Transport design and equipment it's AC, paralleled AC systems,
not readily applicable to our single engine DC systems. Boat stuff
has some of the most applicable ideas to little planes. (food/thought)



BIG PICTURE, MISS MATCHED IDEAS AND PLANES:
The marine stuff has lots of ideas for super systems. I personally have
only one I-VR alternator & battery. The obsession with air transport
category electics in a single engine plane is overkill, and can distract
from an overall goal IMHO (simple, light and cost effective). Regardless
what you do, you have one engine and many single failure points that
are way more critical to your health than wires in your plane.

It is just a thought, take it or leave it, intelligent comments welcomed.

Flame Suit On, Cheers George


---------------------------------
Brings words and photos together (easily) with


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nuckollsr(at)cox.net
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PostPosted: Sun Feb 05, 2006 10:05 am    Post subject: Dual Alternator Use Reply with quote

At 07:03 AM 2/5/2006 -0800, you wrote:

Quote:


>From: "Mark Neubauer" <markn(at)fuse.net> Subject: Dual Alternator Use
> AeroElectric-List message posted by: "Mark Neubauer" <markn(at)fuse.net>

>Being one of Bob's electronic disciples, I was wondering about
the use of my
>B&C 40amp alternator with the SD-8 together in my GlaStar. Is it
OK to use
>them both at the same time, yielding an available current output
of 48 amps,
>or should the SD-8 only be energized when the main alternator is
>disengaged?
.....>
>Are there voltage regulation problems having both alternators pumping
>electrons into the system busses at slightly different set voltages
>(determined by the exact regulator settings)?
>
>Mark Neubauer
Mark:

.....What about running two alternators simultaneously in parallel but
isolated.
The 40 amp does the Yeoman's duty, lets call that the (A) system, and the
SD8 back-up runs say 5 amps of other (B) system items. If the SD8 died
you still have the 40 amp. If the SD8 died you would still have system (A).
If you wanted you could manually cross feed the (B) buss and (A) buss in
event one system died (after suitable load shedding, e.g., turning stuff off).
This is the way the Big (jet) Boys do it. Parallel but isolated.

Cons:
.....-Wt. (1lb) for small 0.8-1.2 amp/hr back-up (B) system battery
.....-You may be able to use a capacitor vs. a battery for the SD8
http://www.batterymart.com/battery.mv?p=SLA-12V1-3
http://www.batterymart.com/battery.mv?p=SLA-12V0-8
Pros:
.....-True redundancy with isolated systems working in parallel
.....-Reduced load on the (A) system alternator (B sys not dead wt.)
.....-One system will not affect the other (good thing)

"Parallel but isolated" doesn't bring a lucid image to mind
but I think Figure Z-14 is what you're talking about.

THE MARINE SOLUTION
If you MUST have dual sync'ed alternators consider the SD-20 and a
marine voltage regulator. I suggest the SD-20 to keep the dual
alternators of the same type. Marine regulators have been paralleling
dual alternators for decades. They don't cost much more than one so
called advanced regulator. They have all the protection you could
every want: Now having different models of alternators with different
power output potential may pose a challenge, but the marine
companies no doubt have a solution. They may be able to parallel the
SD-8 and L-40 even? You would have to ask. (food for thought only).

http://www.amplepower.com/products/sarv3/index.html
http://www.amplepower.com/products/dual_alt/index.html
http://www.amplepower.com/products/sysnav_ic/index.html
http://www.sterling-power.com/
(select>product>adv alternator reg>pro digital)

I am NOT saying this is the way to go about it, but I'm trying to open
your mind. Marine apps. have been making real rugged, reliable and
redundant DC electrical systems for a long time. If you get into real
Air Transport design and equipment it's AC, paralleled AC systems,
not readily applicable to our single engine DC systems. Boat stuff
has some of the most applicable ideas to little planes. (food/thought)

The regulators described are intended to PARALLEL two
alternators (running on perhaps different engines a-la
C-337, Beech Baron, etc.) to a single bus structure
and single battery or batteries in parallel. The engine
driven power sources drive a common bus full time
and cannot be isolated.
Quote:
BIG PICTURE, MISS MATCHED IDEAS AND PLANES:
The marine stuff has lots of ideas for super systems. I personally have
only one I-VR alternator & battery. The obsession with air transport
category electics in a single engine plane is overkill, and can distract
from an overall goal IMHO (simple, light and cost effective). Regardless
what you do, you have one engine and many single failure points that
are way more critical to your health than wires in your plane.

Very few machines being crafted for the OBAM aircraft
community can make use of Z-14 style systems. Dual
electrical systems make sense only when you have dual
cockpit systems both capable of launching into the
worst you intend to traverse. I can't imagine any
airplane short of a fully decked out LAIVP making
good use of Z-14. However, if one plans to have two
alternators, driving them from a common regulator scheme
into a single battery structure doesn't make sense
either. The Main/Aux alternator schemes described in
the Z-Figures ASSUME that at least one alternator
(main) will easily carry ALL of the maximum anticipated
running loads without support from the other alternator
(aux). The duties of the aux alternator are to pick up
minimal needed loads in the RARE event that the main
alternator becomes unavailable.

Paralleling multiple alternators to run full time
into a single bus structure is exactly what the
"big guys" do. Further, they may also depend on both
generators being on line to carry normal max running
loads. This architecture leads to a variety problems
with failure modes, meeting load analysis goals and
supplying 30 minutes of snort when a system designed
to suffer emergencies goes completely dark.

If one plans an all-electric panel, then there's a
vacuum pump pad open. It seems a waste not to plug
that pad with a 4-pound alternator installation which
gives rise to Figure Z-13/8.

This architecture is suited to 99+ percent of any
OBAM aircraft flying wherein the builder would be
willing to launch into his/her favorite IMC in a
Piper Cherokee fitted with a generator and vacuum pump.

Z-13/8 offers a hedge against the vast majority of
single point failures that would have taken the
panel dark in certified ships for the past six
decades for a 4-pound weight penalty. Further, Z-11
is easy to start out with and morph into Z-13/8
at a future time if you feel it's desirable.

If anyone is considering a Z-14 style installation,
let's talk. It's going to be heavier, more complex
and not likely to service your needs in anything
short of an airplane like the Lancair IVP I described
above. If you believe there is a necessity/benefit
from running both alternators full time into a common
bus, let's talk some more. This should not be necessary.

Mark, if you have planned loads in your project that
would overload a 40A machine, please consider a 60A
alternator and keep the SD-8 in relaxed reserve for
what it does best.

It's really easy for the neophyte builder to succumb
to much of what's misunderstood by the general public
(including most pilots) as to what kinds of failures
really put an airplane in jeopardy and what practical
countermeasures will mitigate the risk. Your #1 backup
in ANY airplane is the flashlight and hand-helds in
your flight bag. The rest is icing on the cake. But take
care lest you pile 10 pounds of icing on a two pound
cake. 10 years from now, you will wish that you had that
extra weight carrying ability available for fuel and
baggage (and that the cost-of-ownership dollars had
gone into your retirement account).
Bob . . .


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