 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
nuckolls.bob(at)aeroelect
Guest
|
 Posted: Sun Jan 10, 2021 8:59 pm Post subject: Two charging devices running in parallel? |
 |
|
--> AeroElectric-List message posted by: "rparigoris" <rparigor(at)hotmail.com>
Hi Bob You wrote in a post for RV10: "TWO alternators don't play well running
in tandem unless their regulators are specifically chosen for parallel operation."
Okay, the legacy definition of 'paralleled alternators/generators'
says the two machines are regulated for the same set-point and
ideally, they SHARE the system loads between them.
Many GA twins were fitted with paralleling systems on their
generators. The Beech 18 had some carbon pile regulators . . .
the Cessna 310/320 had some electro-mechanical devices; both
had paralleling coils on their voltage sense magnetics.
To date, I'm aware of NO dual alternator systems in an OBAM
aircraft wherein the two alternators are expected to simultaneously
deliver energy into a system. The B&C standby systems
are fitted with lowered set-point regulators so that they
'auto-switch' when the bus voltage falls below the setpoint
due to main alternator failure.
Tandem operation was never anticipated. Yeah, they were sorta
connected up all the time but they were designed to operate
independently of each other.
My specific question is about my Rotax 914. I will be using a single Earth-X 680C
LiFe battery. It has an internal generator and I am using a B&C AVC1 regulator
with set-point at 14.5 volts. In addition on the vacuum pad I have a B&C LR3D
with set-point at 14.6 volts. The vacuum pad doesn't spin very fast and at
lower RPMs the alternator doesn't put out as much as the internal generator.
Have you discussed this will B&C? I wonder if they have
any customers with field experience on this configuration.
Let's noodle thru this:
The LiFePO4 delivers energy at 13.0 and below. So after
start up the regulators on both alternators will sense
'voltage low' and command their respective machines
to pick up the bus. If rpm is high enough the PM
alternator will pick up system loads at 14.5 . . .
at higher rpm the pad driven alternator will pick
up loads at 14.6 whereupon the PM alternator
will 'relax' until such time as system loads exceed
output of the pad-driven alternator.
The pad driven alternator becomes 'unregulated'
and limited in output only by rpm. Voltage sags
until the PM alternator picks up what's left
over.
Whether or not this is a stable condition
is subject to tests. In this case the alternators
are not sharing system loads. The pad-driven
device is running full-field and the PM alternator
becomes 'system master' and ostensibly will hold
the bus at 14.5.
Looks pretty good on paper . . . do you know
any one who is flying this?
That said the internal generator best be kept to 12 amps or less continuous
amp draw to achieve long life from it. Idea is let the alternator put out
it's best and do as much work as it can as it can do so without worry of over
taxing it. Then if set-point of 14.6 volts can't be maintained the generator
will take over and supplement. I have a shunt to read amp output on both chargers.
Would my plan satisfy "regulators specifically chosen for parallel operation."
Dunno . . . the condition Mr. Booth was citing
is classic behavior for a pair of machines
expected to operate REGULATED and regulator
dynamics causes them to wrestle with each other.
The result is often manifested in wildly
fluctuating field voltages and outputs.
In your case, you never have both alternators
fighting for regulation dominance. One of the
regulators is always hard-over wherein regulation
dynamics are not a factor. Whether or
not the regulators are sufficiently stable to
setpoints that close together remains to be
seen . . . and the spread can always be opened
up a bit.
An interesting experiment!
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
| Back to top |
|
 |
rparigoris
Joined: 24 Nov 2009
Posts: 780
|
| Posted: Mon Jan 11, 2021 5:48 pm Post subject: Re: Two charging devices running in parallel? |
|
|
Hi Bob I spoke with TJ today, he doesn't know of anyone that has done what I propose thus far. After he did a bit of noodling, he thought it will probably work OK. His suggestion was to start with a .2volt spread and could open to .3 or .4 if needed.
I don't know of anyone who is using a LR3D (or C) and a AVC1 at the same time like I propose. AVC1 has not been around too long.
I will add this to the list of Interesting Experiments!
Appreciate your opinion as always. Ron P.
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
