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Aux Alternator B Lead, Battery Buss

 
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Michael Wynn



Joined: 10 Jan 2006
Posts: 148
Location: San Ramon, CA

PostPosted: Sat Feb 06, 2010 8:25 am    Post subject: Aux Alternator B Lead, Battery Buss Reply with quote

Hi all,

I am building an all-electric RV 8 with a rear mounted battery. I was planning to use Z-12 architecture. On this drawing, both the B lead from the main alternator and the B lead from the auxiliary alternator terminate (with appropriate fusing) on the starter contactor hot side and hence to the aircraft side of the main battery contactor. In reviewing the setup recommended by Marc Ausman at Vertical Power (still scratching my head on whether or not to use the system), he recommends connecting the aux alternator B lead to the battery side of the battery contactor. http://verticalpower.com/docs/VP_Config_2.pdf

When I asked him why, he said the following:

We wire the secondary alternator to the battery side of the contactor so that you can still use it if the battery contactor fails. Your normal operating mode is with the battery contactor closed and using the primary alternator. If the primary alternator fails, you can switch over to the secondary alternator. In this failure mode it really doesn't matter which side the secondary alternator is connected to.

Another scenario is that you are flying along and the battery contactor fails. The VP-200 automatically detects this failure, load sheds, opens the battery contactor circuit just to be safe, and then switches over to the backup alternator. The VP-100 will flag the failure, then you have to manually switch to the backup alternator. In either case, the secondary alternator must be on the battery side to operate correctly (the SD-8 is an exception and will generate power without a battery in the loop, but there are too many scenarios to get into the nitty gritty).

Power cannot flow from the alternator backwards through the electronic circuit breakers. So if the battery contactor failed open and both alts are on the bus side, you'd have no way to charge the battery or use it to regulate the bus voltage.

Don't forget the secondary alternator b-lead is a hot wire (since it is connected to the battery) and needs a fuse in back near the battery. This is indicated on the wiring diagram. Also, the sec alt B-lead is usually a 10 or 12 gauge wire, so it is not that big or difficult to route.

From a practical wiring point of view, it would be a lot less wire to put both alternator B-leads to the starter contactor. On the other hand, running a 10 gauge wire to the battery side of the main contactor would then provide you with a way to wire a battery buss in the front of the airplane, as opposed to placing the battery buss next to the battery and running multiple wires to the front.

I also have dual electronic ignition in this bird, so I am planning to place a second, small battery in the front that is dedicated to the second electronic ignition. I don't know if this changes how it should be set up. On an earlier post, Bob had said something about using a modified Z-14 with the endurance buss set up as the secondary shown in Z-14.

Anyway, hope this hasn't been to confusing. This forum and the Aeroelectric book have been an invaluable source of education for a first-time builder.

Regards,

Michael Wynn
RV 8 Finishing
San Ramon, CA
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RV 8
San Ramon, CA
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PostPosted: Sat Feb 06, 2010 12:18 pm    Post subject: Aux Alternator B Lead, Battery Buss Reply with quote

Ausman at Vertical Power (still scratching my head on whether or not
to use the system), he recommends connecting the aux alternator B
lead to the battery side of the battery
contactor. http://verticalpower.com/docs/VP_Config_2.pdf

When I asked him why, he said the following:

We wire the secondary alternator to the battery side of the contactor
so that you can still use it if the battery contactor fails. Your
normal operating mode is with the battery contactor closed and using
the primary alternator. If the primary alternator fails, you can
switch over to the secondary alternator. In this failure mode it
really doesn't matter which side the secondary alternator is connected to.

<snip>

Anyway, hope this hasn't been to confusing. This forum and the
Aeroelectric book have been an invaluable source of education for a
first-time builder.

Keep in mind that when the installation manual for
a system like Vertical Power =or= a Z-figure is
published, the ARCHITECTURE is being crafted to
meet certain design goals. The advice from Marc
embraces the design philosophy for a two-layered
electrical system as described in the notes for
Z-13/8 and illustrated in the companion drawing.

If your design goals are different and you are
satisfied with the failure mode effects for a
new configuration, then by all means . . .

I'm not trying to champion anyone's architectures
as being superior over any another . . . only the
idea that there are REASONS why things are hooked
up a particular way. Be sure you do the homework,
take the exam and are satisfied with the grade
before you shuffle things around.

Bob . . .


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Michael Wynn



Joined: 10 Jan 2006
Posts: 148
Location: San Ramon, CA

PostPosted: Tue Feb 09, 2010 3:18 pm    Post subject: Aux Alternator B Lead, Battery Buss Reply with quote

Thanks for this Bob.

I am trying to do my homework. I am not an electrical engineer and have profited a great deal from what is written here. I guess I don't clearly understand what happens to some of the components in a fail mode.

So the first question is, where does the B-lead from the aux alt go?  If it is connected with the main alt B-lead to the starter side of the main contactor, then the failure mode goes like this:

1. Main alt fails, turn off it's field and turn on the aux alt. Shed load to 80% of the aux alternator rating (80%X20 amp= 16 amp max).
2. If the main contactor fails open, will the main alternator function okay?
3. If the battery shorts ( a rare occurrence, to be sure) then open the main contactor. Does the main alt work okay?
4. Main alt fails followed by a failure of the battery contactor.  Are we still okay?

If the aux alt is connected to the battery side of the battery contactor:

1. Main alt fails, turn off it's field and turn on the aux alt. Shed load to 80% of the aux alternator rating (80%X20 amp= 16 amp max). Not a problem
2. If the main contactor fails open, will the main alt still be okay or do I switch to the aux alternator because it has a direct battery connection?
3. If the battery shorts, that should burn out the fuse between the aux alternator B-lead if that alternator is being used. Is the main still functional?

The question I am getting to, I think, is how does the system perform if the battery is out of the circuit either because the main contactor fails or we have to open it to free us from a failed battery. Back to my original question. Where should the aux alternator B-lead go and why?

Thanks

Michael Wynn
RV 8 Finishing

In a message dated 2/6/2010 12:19:19 P.M. Pacific Standard Time, nuckolls.bob(at)aeroelectric.com writes:
Quote:
[img]res://C:\Program Files\Nuance\NaturallySpeaking10\Program\web_ie.dll/QMARK.GIF[/img][img]res://C:\Program Files\Nuance\NaturallySpeaking10\Program\web_ie.dll/ARROW.GIF[/img]--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>

Ausman at Vertical Power (still scratching my head on whether or not
to use the system), he recommends connecting the aux alternator B
lead to the battery side of the battery
contactor. http://verticalpower.com/docs/VP_Config_2.pdf

When I asked him why, he said the following:

We wire the secondary alternator to the battery side of the contactor
so that you can still use it if the battery contactor fails. Your
normal operating mode is with the battery contactor closed and using
the primary alternator. If the primary alternator fails, you can
switch over to the secondary alternator. In this failure mode it
really doesn't matter which side the secondary alternator is connected to.

<snip>

Anyway, hope this hasn't been to confusing. This forum and the
Aeroelectric book have been an invaluable source of education for a
first-time builder.

Keep in mind that when the installation manual for
a system like Vertical Power =or= a Z-figure is
published, the ARCHITECTURE is being crafted to
meet certain design goals. The advice from Marc
embraces the design philosophy for a two-layered
electrical system as described in the notes for
Z-13/8 and illustrated in the companion drawing.

If your design goals are different and you are
satisfied with the failure mode effects for a
new configuration, then by all means . . .

  I'm not trying to champion anyone's architectures
  as being superior over any another . . . only the
idea that there are REASONS why things are hooked
up a particular way. Be sure you do the homework,
take the exam and are satisfied with the grade
before you shuffle things around.

Bob . . . ========================= Use utilities Day ================================================ - MATRONICS WEB FORUMS ================================================ - List Contribution Web Site sp;   ===================================================


[quote][b]


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Michael Wynn
RV 8
San Ramon, CA
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rleffler



Joined: 05 Nov 2006
Posts: 680

PostPosted: Tue Feb 09, 2010 4:15 pm    Post subject: Aux Alternator B Lead, Battery Buss Reply with quote

Michael,

I’m currently planning a VP-200 implementation at the moment. I’m not an expert, but I’ll share my opinion.

See my comments inline…..

bob

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of MLWynn(at)aol.com
Sent: Tuesday, February 09, 2010 6:17 PM
To: aeroelectric-list(at)matronics.com
Subject: Re: Aux Alternator B Lead, Battery Buss



Thanks for this Bob.



I am trying to do my homework. I am not an electrical engineer and have profited a great deal from what is written here. I guess I don't clearly understand what happens to some of the components in a fail mode.



So the first question is, where does the B-lead from the aux alt go? Config 2 has the alt alternator connected between the battery and the battery contactor. If it is connected with the main alt B-lead to the starter side of the main contactor, then the failure mode goes like this:



1. Main alt fails, turn off it's field and turn on the aux alt. Shed load to 80% of the aux alternator rating (80%X20 amp= 16 amp max). ok

2. If the main contactor fails open, will the main alternator function okay? It should, but your battery won’t charge

3. If the battery shorts ( a rare occurrence, to be sure) then open the main contactor. Does the main alt work okay? It should work just fine.

4. Main alt fails followed by a failure of the battery contactor. Are we still okay? Yes, assuming that the alt alternator is attached between the battery and starter contactors.



If the aux alt is connected to the battery side of the battery contactor:



1. Main alt fails, turn off it's field and turn on the aux alt. Shed load to 80% of the aux alternator rating (80%X20 amp= 16 amp max). Not a problem

2. If the main contactor fails open, will the main alt still be okay or do I switch to the aux alternator because it has a direct battery connection? Yes it’s ok, and yes the alt alternator can charge the battery if needed and drive an e-bus

3. If the battery shorts, that should burn out the fuse between the aux alternator B-lead if that alternator is being used. Is the main still functional? Should be as long as the main alternator hasn’t failed.



The question I am getting to, I think, is how does the system perform if the battery is out of the circuit either because the main contactor fails or we have to open it to free us from a failed battery. Back to my original question. Where should the aux alternator B-lead go and why?

I’m actually working on a slightly different variant, but am asking similar questions. I’m also adding a second battery to config 2 that will drive the endurance buss and can be brought online in parallel if needed for those really cold morning starts. The placement of the back up alternative doesn’t seem to have a significant impact as long as you ensure that only one alternator is on at a time. If it’s behind the battery contactor then you added another failure point in my mind.

I’m planning on giving Marc a call in the morning to discuss.

bob



Thanks



Michael Wynn

RV 8 Finishing



In a message dated 2/6/2010 12:19:19 P.M. Pacific Standard Time, nuckolls.bob(at)aeroelectric.com writes:
Quote:

[img]res://C:\Program%20Files\Nuance\NaturallySpeaking10\Program\web_ie.dll/QMARK.GIF[/img][img]res://C:\Program%20Files\Nuance\NaturallySpeaking10\Program\web_ie.dll/ARROW.GIF[/img]--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>

Ausman at Vertical Power (still scratching my head on whether or not
to use the system), he recommends connecting the aux alternator B
lead to the battery side of the battery
contactor. http://verticalpower.com/docs/VP_Config_2.pdf

When I asked him why, he said the following:

We wire the secondary alternator to the battery side of the contactor
so that you can still use it if the battery contactor fails. Your
normal operating mode is with the battery contactor closed and using
the primary alternator. If the primary alternator fails, you can
switch over to the secondary alternator. In this failure mode it
really doesn't matter which side the secondary alternator is connected to.

<snip>

Anyway, hope this hasn't been to confusing. This forum and the
Aeroelectric book have been an invaluable source of education for a
first-time builder.

Keep in mind that when the installation manual for
a system like Vertical Power =or= a Z-figure is
published, the ARCHITECTURE is being crafted to
meet certain design goals. The advice from Marc
embraces the design philosophy for a two-layered
electrical system as described in the notes for
Z-13/8 and illustrated in the companion drawing.

If your design goals are different and you are
satisfied with the failure mode effects for a
new configuration, then by all means . . .

I'm not trying to champion anyone's architectures
as being superior over any another . . . only the
idea that there are REASONS why things are hooked
up a particular way. Be sure you do the homework,
take the exam and are satisfied with the grade
before you shuffle things around.

Bob . . . Use utilities Day ======================= - MATRONICS WEB FORUMS ======================= - List Contribution Web Site sp; =


http://www.matronics.com/Navigator?AeroElectric-List
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PostPosted: Tue Feb 09, 2010 7:37 pm    Post subject: Aux Alternator B Lead, Battery Buss Reply with quote

At 05:17 PM 2/9/2010, you wrote:
Quote:
Thanks for this Bob.

I am trying to do my homework. I am not an electrical engineer and have profited a great deal from what is written here. I guess I don't clearly understand what happens to some of the components in a fail mode.

So the first question is, where does the B-lead from the aux alt go? If it is connected with the main alt B-lead to the starter side of the main contactor, then the failure mode goes like this:

Which Z-figure, if any, are you considering.
Quote:

1. Main alt fails, turn off it's field and turn on the aux alt. Shed load to 80% of the aux alternator rating (80%X20 amp= 16 amp max).
v
The 80% rule is about maintaining some "excess" capability
for the recharging of batteries. If you've had a main
alternator failure then getting comfortably on the
ground is the mission of the moment. Use 100% of the
aux alternator if necessary . . . plus what ever is
in the battery to boot.

What are your "get down comfortably loads" as compared
to your aux alternator size?

Quote:
2. If the main contactor fails open, will the main alternator function okay?

Probably but not guaranteed. Does your airplane have
a hydraulic pump . . . or klieg lights for landing?

Quote:
3. If the battery shorts ( a rare occurrence, to be sure) then open the main contactor. Does the main alt work okay?

RB batteries very rarely short . . . during the
time the 5-cell battery is connected to the bus,
the alternator is stuffing 14v into a 11.8
volt system . . . the loadmeter (if installed will
show abnormally high amps while bus volts are low.
This condition is not stable. As the battery
dries up, the voltage will rise and the current
may go down a bit. This is so rare with an RG
battery that what ever diagnostic and reaction
plans you have concocted for such an event will
probably have been forgotten.

Quote:
4. Main alt fails followed by a failure of the battery contactor. Are we still okay?

That's a dual failure on a single flight. Also
depends on what z-figure you're talking about.

Quote:

If the aux alt is connected to the battery side of the battery contactor:

Don't recommend that for the SD-20 . . . that's
fraught with the same issues as the previously
published and recently withdrawn Z-13/20. If
you have an SD-20, go with a Z-12 emulation
and put the aux alternator on the ship-side
of the battery contactor.

Quote:

1. Main alt fails, turn off it's field and turn on the aux alt. Shed load to 80% of the aux alternator rating (80%X20 amp= 16 amp max). Not a problem
2. If the main contactor fails open, will the main alt still be okay or do I switch to the aux alternator because it has a direct battery connection?
3. If the battery shorts, that should burn out the fuse between the aux alternator B-lead if that alternator is being used. Is the main still functional?

The question I am getting to, I think, is how does the system perform if the battery is out of the circuit either because the main contactor fails or we have to open it to free us from a failed battery. Back to my original question. Where should the aux alternator B-lead go and why?

If it were my airplane, Z-13/8 is the lightest,
simplest, least expensive way to get SYSTEM
reliability not offered by the majority of TC
aircraft. Just how close Vertical Power comes to
emulating Z-13/8 performance has not been
fully explored by me . . . Marc would be
your authority on that. But as I mentioned
above, an SD-20 should be paired with the
SB-1 regulator, connected to the main bus
and adjusted for 13.0 volts. Operate per B&C
instructions.

Bob . . . [quote][b]


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