Today's Message Index:
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1. 08:06 AM - Re: New role for the E-Bus? (user9253)
2. 08:20 AM - Re: Re: New role for the E-Bus? (Robert L. Nuckolls, III)
3. 10:57 AM - Re: Re: New role for the E-Bus? (Charlie England)
4. 05:30 PM - Re: New role for the E-Bus? (johnbright)
Message 1
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| Subject: | Re: New role for the E-Bus? |
Charlie,
There is no reason to have the start push button connected to the engine bus.
The master contactor must be closed to crank the engine. So the start button
might as well be connected to the main power bus.
If the bus tie switch happens to be closed while starting the engine, then
starter current will flow through that switch. If you must have that switch,
then use a DPDT switch with half of the switch in series with the start push button.
Wire the DPDT switch so that when the bus tie is closed, the starter is disabled.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=494988#494988
Message 2
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| Subject: | Re: New role for the E-Bus? |
>
>I'm not following the 'FAR 23' issue with relays at the engine bus
>for downstream stuff.
>A fuse at the bus protects everything downstream of the fuse.
The 'issue' concerns maximum circuit
protection for always hot feeders. Classically,
the FAA has holy watered 5A as a maximum.
Which doesn't make much sense to me . . .
There's a huge difference in energy released
in a short wire downstream of fuses versus
breakers and 14v vs. 28v.
The legacy backstop was to add disconnect
at the battery . . . relay, contactor etc.
>When I did failure analysis for my single battery/dual alt,
>electrically dependent alternative engine, it looked like any
>conventional arrangement of dual alts with control fed by the main
>bus and B leads *to* the main bus, would result in the loss of both
>alts if the master is turned off ('smoke in the cockpit'). I chose
>to route one alt's B lead directly to the engine bus, making it
>effectively a dedicated electrical power source for the engine,
>controlled via the engine bus. Goal was to preserve 'classical'
>engine independence, and not depend on the limited energy in the
>battery to complete the flight. There is still a cross-tie switch
>between engine and main buses, to maintain alt failure redundancy.
>Is there a problem with this approach?
Don't think so . . . but schematics speak
far more clearly than words. Could you sketch
your architecture and scan or photograph it
for sharing?
Sorry for the delay. Got a 'bug' last Friday
night and I'm just now getting up and around. . .
Bob . . .
Message 3
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| Subject: | Re: New role for the E-Bus? |
On 2/25/2020 10:06 AM, user9253 wrote:
>
> Charlie,
> There is no reason to have the start push button connected to the engine bus.
> The master contactor must be closed to crank the engine. So the start button
> might as well be connected to the main power bus.
> If the bus tie switch happens to be closed while starting the engine, then
> starter current will flow through that switch. If you must have that switch,
> then use a DPDT switch with half of the switch in series with the start push
button.
> Wire the DPDT switch so that when the bus tie is closed, the starter is disabled.
>
> --------
> Joe Gores
Hi Joe,
As I said in the reply to Bob, most of the loads in the drawing are
'artifacts' of copy/paste operations from a basic AEC drawing to my
Paint program. The only items of significance for our discussion at the
moment are the two alternators and the way they connect to the system,
vs connecting both to the main bus as shown in other AEC drawings.
I'll ponder the bus tie issue. The reason it's there is a convenient way
to get alternator/battery to the main bus if there's a failure in the
master control path causing the master contactor to open.
Thanks,
Charlie
Message 4
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| Subject: | Re: New role for the E-Bus? |
ceengland7(at)gmail.com wrote:
> RE: the FAR23 issue, I was referring to a drawing posted earlier that had multiple
relays fed from a bus which itself was already controlled. Most of the loads
could have been handled easily by switches.
>
>
> Charlie
Thanks Charlie... I noticed that... my latest thinking attached.
--------
John Bright, RV-6A, at FWF, O-360
Single batt dual alt SDS EM-5-F.
john_s_bright@yahoo.com, Newport News, Va
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=494992#494992
Attachments:
http://forums.matronics.com//files/elec_schem_1_batt_2nd_alt_on_batt_4_cyl_sds_em_5_f_rev_initial_release_simple_view_907.pdf
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