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gerry.vandyk(at)eastlink.
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 Posted: Thu Dec 28, 2023 3:32 pm Post subject: Tailwind Electrical System Drawing and Power Analysis |
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Hello again allWell, I think I'm ready for a good critique on my proposed electrical system for my Tailwind project. For the most part it's based on Z13/8, we're using a Plane Power AL12-E160 primary alternator, and of course the B&C SD-8 backup alternator. The E160 is internally regulated, and also has an internal crowbar system and alt-out panel light output, which I intend to use. The SD-8 has their older PMR1 regulator, so we've got the external crowbar module and no voltage sensing. I've drawn these items as shown on their respective install instructions call for.
As I mentioned earlier, I intended to start the engine on the endurance bus, and check the SD-8 operation during the startup procedure. I had neglected to think about where the starter was going to get power from, so the idea has forced an additional switch and relay (a rather robust one at that) to run the main bus. The battery contactor would be closed for startup, then the SD-8 operation checked and finally the main bus would be brought up to begin normal operation.
I'm a little uneasy about this extra switching, as I know this group is inclined toward fewer failure points, and with good reason. As I look at the 'textbook' Z13/8 drawing, with my dual EFIS, IFR capable panel in mind, it seems to me that a startup would bring the entire panel up with the main bus, then with the engine running I'd have to close the E-bus switch, open the battery contactor, dropping out half the instrument panel. Then check the backup alternator operation, and finally reboot the rest of the panel again. It just really feels rather clunky to me.
Bob, have I missed something with the original architecture concept? Is there a way to check the backup alternator function while the main bus is up and running? It would certainly help me simplify my system.
I'd appreciate if you good folks would give my drawing a good review. Questions, comments and critiques are all welcome.
Thanks again
Gerry van Dyk
Tailwind C-GVDZ
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peter(at)sportingaero.com
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| Posted: Fri Dec 29, 2023 1:11 am Post subject: Tailwind Electrical System Drawing and Power Analysis |
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Why do you want to switch the SD-8 alternator?
Why switch battery power to the bus twice?
Use an externally regulated main alternator to avoid having to switch the alternator output.
Provide a method to connect the battery directly to the bus.
Do not use a diode in the feed to the essential bus.
There are a number of services connected directly to the battery just waiting to flatten it…
If the voltage of the SD8 is set (say) 0.2v lower than the main alternator it will not produce power if the main is on line. If the main fails it takes up the load.
For my liking you have too many relays between the battery and the bus bar.
If you use an externally regulated main alternator then initially only switch on the SD8 on start up. Then power up the main alternator regulator and bring that on line.
Install a switch that powers up the essential (or main) bus directly from the battery, if the switch is a double pole use the second pole to disable the starter.
The large diode in the feed line to the essential bus will always drop the voltage by an amount. The benefit is auto load shedding but do you need that with 2 alternators? If you really want to shed the main bus use a large switch and ensure there is a path to the essential bus directly from the battery. I used to have a feed diode and would not use one again.
A diode is very beneficial on the starter contactor.
Having a low voltage waring that is independent of the EFIS is useful. It is possible you will get immune to EFIS warnings…
Peter
From: owner-aeroelectric-list-server(at)matronics.com <owner-aeroelectric-list-server(at)matronics.com> On Behalf Of Gerry van Dyk
Sent: Thursday, December 28, 2023 11:32 PM
To: aeroelectric-list(at)matronics.com
Subject: Tailwind Electrical System Drawing and Power Analysis
Hello again all
Well, I think I'm ready for a good critique on my proposed electrical system for my Tailwind project. For the most part it's based on Z13/8, we're using a Plane Power AL12-E160 primary alternator, and of course the B&C SD-8 backup alternator. The E160 is internally regulated, and also has an internal crowbar system and alt-out panel light output, which I intend to use. The SD-8 has their older PMR1 regulator, so we've got the external crowbar module and no voltage sensing. I've drawn these items as shown on their respective install instructions call for.
As I mentioned earlier, I intended to start the engine on the endurance bus, and check the SD-8 operation during the startup procedure. I had neglected to think about where the starter was going to get power from, so the idea has forced an additional switch and relay (a rather robust one at that) to run the main bus. The battery contactor would be closed for startup, then the SD-8 operation checked and finally the main bus would be brought up to begin normal operation.
I'm a little uneasy about this extra switching, as I know this group is inclined toward fewer failure points, and with good reason. As I look at the 'textbook' Z13/8 drawing, with my dual EFIS, IFR capable panel in mind, it seems to me that a startup would bring the entire panel up with the main bus, then with the engine running I'd have to close the E-bus switch, open the battery contactor, dropping out half the instrument panel. Then check the backup alternator operation, and finally reboot the rest of the panel again. It just really feels rather clunky to me.
Bob, have I missed something with the original architecture concept? Is there a way to check the backup alternator function while the main bus is up and running? It would certainly help me simplify my system.
I'd appreciate if you good folks would give my drawing a good review. Questions, comments and critiques are all welcome.
Thanks again
Gerry van Dyk
Tailwind C-GVDZ
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