 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
mddickens(at)comcast.net
Guest
|
 Posted: Tue Sep 04, 2012 10:05 am Post subject: Backup Alternator Wiring |
 |
|
<![endif]-->
I am starting off with drawing Z-12 as a basis for my architecture and am wondering if there would be an issue with connecting the backup alternator B lead to the battery side of the battery contactor instead of the starter contactor side. The field would also be powered and switched off of the E-Buss. The reason I am interested in doing this is to address the possibility of a battery contactor or master switch failure, so that the battery could be charged as I ran on the E-Buss. I’ve never seen it wired this way, so I assume there’s a problem with it, but I am not seeing it. Normal 0 false false false EN-US X-NONE X-NONE <![endif]--> <![endif]--> /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} <![endif]-->
[quote][b]
| | - 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 |
|
 |
nuckolls.bob(at)aeroelect
Guest
|
| Posted: Tue Sep 04, 2012 10:35 am Post subject: Backup Alternator Wiring |
|
|
At 01:04 PM 9/4/2012, you wrote:
I am starting off with drawing Z-12 as a basis for my architecture
and am wondering if there would be an issue with connecting the
backup alternator B lead to the battery side of the battery contactor
instead of the starter contactor side. The field would also be
powered and switched off of the E-Buss. The reason I am interested in
doing this is to address the possibility of a battery contactor or
master switch failure, so that the battery could be charged as I ran
on the E-Buss. I've never seen it wired this way, so I assume there's
a problem with it, but I am not seeing it.
No 'problem' I perceive. It does violate the
legacy design goal for "max cold" wiring when
the battery contactor is open . . . your b-lead
is always hot. But this is a minor if not insignificant
worry. You'd need to be aware of it when working
around the rear of your standby alternator . . .
in cars it's recommended that one disconnect
the (-) battery cable during maintenance ops.
Bob . . .
| | - 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 |
|
|
mddickens(at)comcast.net
Guest
|
| Posted: Tue Sep 04, 2012 10:56 am Post subject: Backup Alternator Wiring |
|
|
Thanks. Looking at it harder, I see that doing this really isn't necessary since the current would get back to the battery through the "back door", traveling through the main power buss across the e-buss diode and back upstream to the battery. Sound right?
From: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>
To: aeroelectric-list(at)matronics.com
Sent: Tuesday, September 4, 2012 1:34:27 PM
Subject: Re: Backup Alternator Wiring
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>
At 01:04 PM 9/4/2012, you wrote:
I am starting off with drawing Z-12 as a basis for my architecture
and am wondering if there would be an issue with connecting the
backup alternator B lead to the battery side of the battery contactor
instead of the starter contactor side. The field would also be
powered and switched off of the E-Buss. The reason I am interested in
doing this is to address the possibility of a battery contactor or
master switch failure, so that the battery could be charged as I ran
on the E-Buss. I've never seen it wired this way, so I assume there's
a problem with it, but I am not seeing it.
No 'problem' I perceive. It does violate the
legacy design goal for "max cold" wiring when
the battery contactor is open . . . your b-lead
is always hot. But this is a minor if not insignificant
worry. You'd need to be aware of it when working
around the rear of your standby alternator . . .
in cars it's recommended that one disconnect
the (-) battery cable during maintenance ops.
Bob . . .
| | - 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 |
|
|
nuckolls.bob(at)aeroelect
Guest
|
| Posted: Tue Sep 04, 2012 11:48 am Post subject: Backup Alternator Wiring |
|
|
At 01:56 PM 9/4/2012, you wrote:
Thanks. Looking at it harder, I see that doing this really isn't
necessary since the current would get back to the battery through the
"back door", traveling through the main power buss across the e-buss
diode and back upstream to the battery. Sound right?
No, the e-bus diode is not intended to be a
charge-path to the battery. The e-bus is intended
to be an ENDURANCE bus that powers only those
devices need to get you to airport in sight
at intended destination. In other words, better
endurance battery only than that of fuel aboard.
If you have an alternator operating, then
plan-b loads can include a combination of
e-bus -AND- main bus loads that do not exceed
alternator capability. But if that alternator
is not available, then the E-BUS PLAN-C takes
effect.
The e-bus is probably the least understood feature
of the z-figures. The design goal is to prevent
any single failure of an electrical system component
from becoming a 'wet-armpits' situation. This
means NOT having to operate on your flight-bag
hand-helds for continued flight to airport of
intended destination.
You ARE planning flight-bag backups . . . right?
http://tinyurl.com/4xjhgly
This means that the e-bus is not intended to
keep everything except the kitchen sink
running. It's intended to keep the flight-bag
backups in comfortable reserve. Hence the small
normal feed diode and relatively small feeder
to the e-bus.
Figure Z-13/8 supports an 8A e-bus while
holding the battery in complete reserve for
descent and approach to landing. Wiring your
20A pad driven alternator as you described
suggests that the e-bus loads can go up to
20 amps . . . with appropriately upsized
feeders.
http://tinyurl.com/756ydec
But in no case should design goals include
charging the battery through the e-bus normal
feed path diode.
Bob . . .
| | - 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 |
|
|
mddickens(at)comcast.net
Guest
|
| Posted: Tue Sep 04, 2012 12:03 pm Post subject: Backup Alternator Wiring |
|
|
Yes, of course, as I have for over 30 years, but I am asking if my reading of the diagram is correct that the current would travel back up the e-buss to provide any charging to the battery, or is the forward rating of the diode not sufficient for this. One is a philosophical discussion (and I agree with you) and the other is an electrical discussion, which is where my question came from. If I'm wrong that the battery gets no charging through this path, I'll simply plan on putting the standby alternator B lead on the battery side of the battery contactor, with the understanding that the B lead will be hot all the time.
From: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>
To: aeroelectric-list(at)matronics.com
Sent: Tuesday, September 4, 2012 2:47:06 PM
Subject: Re: Backup Alternator Wiring
--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>
At 01:56 PM 9/4/2012, you wrote:
Thanks. Looking at it harder, I see that doing this really isn't
necessary since the current would get back to the battery through the
"back door", traveling through the main power buss across the e-buss
diode and back upstream to the battery. Sound right?
No, the e-bus diode is not intended to be a
charge-path to the battery. The e-bus is intended
to be an ENDURANCE bus that powers only those
devices need to get you to airport in sight
at intended destination. In other words, better
endurance battery only than that of fuel aboard.
If you have an alternator operating, then
plan-b loads can include a combination of
e-bus -AND- main bus loads that do not exceed
alternator capability. But if that alternator
is not available, then the E-BUS PLAN-C takes
effect.
The e-bus is probably the least understood feature
of the z-figures. The design goal is to prevent
any single failure of an electrical system component
from becoming a 'wet-armpits' situation. This
means NOT having to operate on your flight-bag
hand-helds for continued flight to airport of
intended destination.
You ARE planning flight-bag backups . . . right?
http://tinyurl.com/4xjhgly
This means that the e-bus is not intended to
keep everything except the kitchen sink
running. It's intended to keep the flight-bag
backups in comfortable reserve. Hence the small
normal feed diode and relatively small feeder
to the e-bus.
Figure Z-13/8 supports an 8A e-bus while
holding the battery in complete reserve for
descent and approach to landing. Wiring your
20A pad driven alternator as you described
suggests that the e-bus loads can go up to
20 amps . . . with appropriately upsized
feeders.
http://tinyurl.com/756ydec
But in no case should design goals include
charging the battery through the e-bus normal
nbsp; -Matt D==============
[quote][b]
| | - 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 |
|
|
nuckolls.bob(at)aeroelect
Guest
|
| Posted: Tue Sep 04, 2012 1:51 pm Post subject: Backup Alternator Wiring |
|
|
At 03:03 PM 9/4/2012, you wrote:
| Quote: | Yes, of course, as I have for over 30 years, but I am asking if my
reading of the diagram is correct that the current would travel back
up the e-buss to provide any charging to the battery, or is the
forward rating of the diode not sufficient for this. One is a
philosophical discussion (and I agree with you) and the other is an
electrical discussion, which is where my question came from. If I'm
wrong that the battery gets no charging through this path, I'll
simply plan on putting the standby alternator B lead on the battery
side of the battery contactor, with the understanding that the B
lead will be hot all the time.
|
The diode adds a voltage drop that hampers
full charge of the battery . . . but probabilities
suggest that battery was fully charged when the
main alternator failed. So if the diode and
associated wiring are beefy enough to carry
output of both alternators as potential
recharge current + e-bus loads . . . then yeah
. . . it plays as a low risk mode-D for system
operation.
We're really thrashing a will-o-the-wisp
in the constellation of hazards to flight.
Electrical system failures figure in a very
small percentage of incidents that bend
airplanes or people. Figure Z-12 is installed
in thousands of TC aircraft and Z-11 is installed
in tens of thousands of TC aircraft . . . admittedly,
the FEMA studies on these aircraft were blessed
more than 50 years ago . . . but over the history
of batteries and alternators on flying machines,
main contactor failure rates are so low as to
be statistically insignificant for cost of ownership
and risks.
Charging the battery though the e-bus normal feed
path are requires that all the components be sized
for worst case current flows. In this case it
would be at least full output of the main
alternator combined with an autoswitched SB
alternator output feeding e-bus loads + battery
recharge loads. If this is a design goal, it can
be done.
Which begs the question. How will you know when
a contactor has faiied?
Bob . . .
| | - 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
