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OV sensing in Z-12

 
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ceengland7(at)gmail.com
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PostPosted: Mon May 21, 2018 2:27 pm    Post subject: OV sensing in Z-12 Reply with quote

Well, I'm starting to question my powers of analysis (or at least my memory). While pondering OV protection with dual alternators (using something less expensive than the B&C units), I perused drawing Z-12. Should I assume that the aux alternator must be left disabled until needed? It appears that having both alts on line would result in both OV protection circuits firing, if either alt had an OV event.  

What I'd like to achieve (alternative engine with auto style engine control) is both alternators (identical capacity) operating all the time, with OV protection taking out only the bad alternator. 
Thoughts?
Charlie
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PostPosted: Mon May 21, 2018 3:25 pm    Post subject: Re: OV sensing in Z-12 Reply with quote

Charlie,
I agree that both over-voltage modules would trip simultaneously.
Options:
1. Like you said, only turn on one alternator at a time.
2. Insert diodes 747-DSA300i45NA in the alternator B leads and connect the over-voltage protection upstream of each diode.
3. Monitor the current on each B lead. In an over voltage condition, shut off only the alternator that is putting out the highest current. This option requires the design of an electronic circuit.


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PostPosted: Mon May 21, 2018 4:48 pm    Post subject: OV sensing in Z-12 Reply with quote

At 05:25 PM 5/21/2018, you wrote:
Quote:
Well, I'm starting to question my powers of analysis (or at least my memory). While pondering OV protection with dual alternators (using something less expensive than the B&C units), I perused drawing Z-12. Should I assume that the aux alternator must be left disabled until needed? It appears that having both alts on line would result in both OV protection circuits firing, if either alt had an OV event.

The B&C SB-1 controller features automatic enabling
of the standby alternator upon failure of the main
alternator . . . along with an annunciator system
to notify the pilot of the event.

One COULD use a more generic controller and
forego up the auto switching/annunciation feature.

You still need low voltage annunciation. If you get
a light, you turn the main alternator OFF; the standby
alternator ON.

The B&C products do feature 'selective trip' . . . a
circuit that deduces whether or not the client
alternator is the source of the ov event. But
with only one alternator operating at any time,
plain vanilla ov protection will function as desired.


Quote:
What I'd like to achieve (alternative engine with auto style engine control) is both alternators (identical capacity) operating all the time, with OV protection taking out only the bad alternator.

Why two alternators ON at the same time? Making
the transition from main to s/b alternator is
not a 'tense' event. If the main alternator quits,
you can finish your cup of coffee and fold the
map up before you start flipping switches. The
auto-change and annunciation were features that
were more bells-and-whistles designed to tickle
the fancy of A36 drivers and Beech engineers.
It was easy to do as we wanted to monitor b-lead
current on the SD20 and enable easy load shedding.
If you're wanting to run two full sized alternators,
then I would agree that the SB-1 if a bit of over-kill.

If it were my airplane, they would be alternator #1
and #2 and swap back and forth in preflight.



Bob . . .


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PostPosted: Mon May 21, 2018 4:51 pm    Post subject: OV sensing in Z-12 Reply with quote

At 06:25 PM 5/21/2018, you wrote:
Quote:
--> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com>

Charlie,
I agree that both over-voltage modules would trip simultaneously.
Options:
1. Like you said, only turn on one alternator at a time.

I like that . . .

Quote:
2. Insert diodes 747-DSA300i45NA in the alternator B leads and connect the over-voltage protection upstream of each diode.
3. Monitor the current on each B lead. In an over voltage condition, shut off only the alternator that is putting out the highest current. This option requires the design of an electronic circuit.

Achhh! . . . Joseph . . . go wash your mouth out with soap.
You go to bed without your Oreos and milk . . .



Bob . . .


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user9253



Joined: 28 Mar 2008
Posts: 1234
Location: Riley TWP Michigan

PostPosted: Mon May 21, 2018 6:02 pm    Post subject: Re: OV sensing in Z-12 Reply with quote

I can handle the soap in my mouth.
But I am NOT going to bed without my Oreos and milk!


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PostPosted: Mon May 21, 2018 7:55 pm    Post subject: OV sensing in Z-12 Reply with quote

On 5/21/2018 7:47 PM, Robert L. Nuckolls, III wrote:

Quote:
At 05:25 PM 5/21/2018, you wrote:
Quote:
Well, I'm starting to question my powers of analysis (or at least my memory). While pondering OV protection with dual alternators (using something less expensive than the B&C units), I perused drawing Z-12. Should I assume that the aux alternator must be left disabled until needed? It appears that having both alts on line would result in both OV protection circuits firing, if either alt had an OV event.

The B&C SB-1 controller features automatic enabling
of the standby alternator upon failure of the main
alternator . . . along with an annunciator system
to notify the pilot of the event.

One COULD use a more generic controller and
forego up the auto switching/annunciation feature.

You still need low voltage annunciation. If you get
a light, you turn the main alternator OFF; the standby
alternator ON.

The B&C products do feature 'selective trip' . . . a
circuit that deduces whether or not the client
alternator is the source of the ov event. But
with only one alternator operating at any time,
plain vanilla ov protection will function as desired.


Quote:
What I'd like to achieve (alternative engine with auto style engine control) is both alternators (identical capacity) operating all the time, with OV protection taking out only the bad alternator.

Why two alternators ON at the same time? Making
the transition from main to s/b alternator is
not a 'tense' event. If the main alternator quits,
you can finish your cup of coffee and fold the
map up before you start flipping switches. The
auto-change and annunciation were features that
were more bells-and-whistles designed to tickle
the fancy of A36 drivers and Beech engineers.
It was easy to do as we wanted to monitor b-lead
current on the SD20 and enable easy load shedding.
If you're wanting to run two full sized alternators,
then I would agree that the SB-1 if a bit of over-kill.

If it were my airplane, they would be alternator #1
and #2 and swap back and forth in preflight.



Bob . . .
No disagreement on your points. What's driving my thought exercise is the attempt to integrate my very different engine subsystem and have the a/c operationally function as close as is reasonably possible to 'traditional' operation with a conventional mags & carb Lyc. I already have the engine bus fed directly from the battery through a high current switch, independent of the a/c master contactor, and tentatively, one alternator feeding there, as well. The other alt feeds the load side of the master contactor (typical tie point).

I'm probably overthinking this, as usual...

Thanks,

Charlie
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