Today's Message Index:
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1. 09:31 AM - Re: Electrical System Schematic Review (jonlaury)
2. 12:12 PM - Re: Re: Electrical System Schematic Review (Robert L. Nuckolls, III)
3. 03:00 PM - Re: Electrical System Schematic Review (user9253)
Message 1
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| Subject: | Re: Electrical System Schematic Review |
Joe, thanks.
The correction is on Rev. B that I'll post this morning.
I have one other question and then I think I've got this knocked.
>From the Ebus alt feed contactor to the Ebus, there is a fusible link called for.
My Ebus is fused at 30a at the battery bus and will run at about 20-24 amps
and I'm using an 8AWG wire to keep temps down so the fuse link would be a 12AWG.
I think that I will put a 40a at the batt bus for the 8AWG protection and
to give some head room for the Ebus. Would it be a better design to use a 30a
ANL current limiter in place of the 12AWG Fuselink?
John
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=306095#306095
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| Subject: | Re: Electrical System Schematic Review |
At 11:29 AM 7/23/2010, you wrote:
>
>Joe, thanks.
>
>The correction is on Rev. B that I'll post this morning.
>
>I have one other question and then I think I've got this knocked.
>
> >From the Ebus alt feed contactor to the Ebus, there is a fusible
> link called for. My Ebus is fused at 30a at the battery bus and
> will run at about 20-24 amps and I'm using an 8AWG wire to keep
> temps down so the fuse link would be a 12AWG. I think that I will
> put a 40a at the batt bus for the 8AWG protection and to give some
> head room for the Ebus. Would it be a better design to use a 30a
> ANL current limiter in place of the 12AWG Fuselink?
I thing the concept for an E-bus has run off
into the weeds. The original idea for
the e-bus was to craft a plan-b that offered
an option for a system that would take you
comfortably to airport of intended destination . . .
battery only. When vacuum pumps started dropping
like flies, we reasoned that e-bus loads could
take a jump by supplementing a battery with
an 8A engine driven power source. Even then,
sizing of continuous operating loads during
an alternator failure event was still LIMITED.
A modicum of planning was necessary to craft the
optimal plan-b.
Your aux alternator is large enough to run
all normal operating loads of 99% of all OBAM
aircraft flying. Hence, the notion of segmenting
electrical loads into "normal" and "endurance"
camps for the purpose optimizing battery-only
operations is curious.
With a 40A aux alternator one is inclined
to run a battery until it croaks . . .
If you're not running a battery maintenance
program designed to maintain some required reserve
capacity, then the whole idea of an e-bus is moot.
Further, the notion of battery-only operations
for a electrically dependent engine under the best
of conditions is a scenario most system designers
would rather not contemplate.
I'll suggest you stand back and review the
big picture. Consider something like Figure
Z-12 and no e-bus. This is how hundreds of
TC aircraft are configured to integrate robust
alternators into the electrical system.
Before you get deeply distracted with
the details of what fuse or diode goes
where, you need to Work through anticipated
failure modes and see first how ARCHITECTURE
mitigates those failures. Keep in mind that
crafting a preventative maintenance plan
unique to your needs marches hand-in-hand
with architecture and sizing of hardware.
I think you'll find that a Z-12 basis for
your proposed system is simpler, easier to
operate, and better suited to an airplane
with an electrically dependent engine.
Bob . . .
Message 3
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| Subject: | Re: Electrical System Schematic Review |
> Would it be a better design to use a 30a ANL current limiter in place of the
12AWG Fuselink?
Short answer is no.
The long answer is that I agree with Bob that the electrical system is much more
heavy duty than most airplanes. If you are sure that you need this redundancy
for IFR over hostile terrain or whatever, then this is what I would do. Get
rid of the fuse at the battery bus and mount the E-Bus relay as close to the
battery as possible and use a 14awg wire (fuselink) between the battery bus and
the relay. Put a 30amp ANL at the relay in series with 10awg to the E-bus.
I am not saying that this is the right way to do it, just the way that I would
do it. Your way will work too. Keep in mind that it will difficult to blow
a 40amp ANL fuse or even a 30 amp for that matter. Use double insulation where
the wire passes though the firewall or bulkheads and take care with the installation
and a fuse will never blow, nor will there be smoke. I am heading
for OSH.
Joe
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=306116#306116
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