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Sequence for bringing alternators on line.

 
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nuckolls.bob(at)aeroelect
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PostPosted: Wed Jun 13, 2018 5:20 am    Post subject: Sequence for bringing alternators on line. Reply with quote

At 05:46 PM 6/12/2018, you wrote:
Quote:
I am writing checklists for a new homebuilt I will be doing the flight testing on. Aircraft has a 40A main alternator and an SD-8 backup alternator. The alternator switch allows either the main or backup alternator to be on and also has an off position. I'm thinking of leaving the switch on the main alternator all the time, except for a test of the SD-8 during the runup. Does anyone see a problem with this plan or should I wait until the load on the electrical system has come down to a certain point before switching to the SD-8? As far as I know the SD-8 will put out whatever it can and any load in excess will simply come from the battery.

Sequencing optoins are not critical. The alternator(s)
may be off or on before starting . . . and order of
shutdown at stopping is similarly unimportant.
[img]cid:.0[/img]


Quote:
Is it reasonable to test the SD-8 every flight or is this something that can be done on a monthly or quarterly basis? Also I have run into a couple pilots recently who start their engines with the alternator off in order to "prevent damage to the alternator during start". I can't remember any mention of this in the AEC. Is there any basis for this? Should I turn the alternator off before shutdown and then on after startup?

The SD8 is very reliable . . . especially
when held in reserve, It's output at
run-up rpm will be rather limited. If you
run up at 1800 rpm, the SD8 will be turning
~2340 and produce about 4A of output.

Depending on the type and condition of
battery . . . and system loads . . .
you'll need to look closely at
bus voltage to make sure it changes
upward by any observable amount
when turned ON.

Testing ever so often while in-flight
would be easier to do . . . you can also
use the flight test to verify your plan-b
loads such that the battery is not discharged
during the en route phase of flight and
held in reserve for descent, approach
and landing.

The risk of damaging an alternator
or other electrowhizzies by the mismanagemet
of alternator switches during normal operations
is a myth. You may sequence their switching
in any manner that makes sense to you.



Bob . . .


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trigo(at)mail.telepac.pt
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PostPosted: Wed Jun 13, 2018 7:17 am    Post subject: Sequence for bringing alternators on line. Reply with quote

Bob

Are your assertions below, about the SD-8, also valid for the SD-20 (now BC-410H)?
Thanks
Carlos

Enviado do meu iPhone

No dia 13/06/2018, às 14:19, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>
Quote:
The SD8 is very reliable . . . especially
when held in reserve, It's output at
run-up rpm will be rather limited. If you
run up at 1800 rpm, the SD8 will be turning
~2340 and produce about 4A of output.

Depending on the type and condition of
battery . . . and system loads . . .
you'll need to look closely at
bus voltage to make sure it changes
upward by any observable amount
when turned ON.

Testing ever so often while in-flight
would be easier to do . . . you can also
use the flight test to verify your plan-b
loads such that the battery is not discharged
during the en route phase of flight and
held in reserve for descent, approach
and landing.

The risk of damaging an alternator
or other electrowhizzies by the mismanagemet
of alternator switches during normal operations
is a myth. You may sequence their switching
in any manner that makes sense to you.



Bob . . .


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nuckolls.bob(at)aeroelect
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PostPosted: Wed Jun 13, 2018 8:01 am    Post subject: Sequence for bringing alternators on line. Reply with quote

At 10:29 AM 6/13/2018, you wrote:
Quote:
Regarding the SD 20, does anybody know what its output should at 1,000 RPM (engine idle) and also at 2400 RPM Cruise?

Thanks,


See https://goo.gl/m6i8qR

At engine 1000 rpm, alternator rpm is about 1300 . . .
you might see 5 or so amps.

At engine 2400, alternator 3,000 the chart
says 29A



Bob . . .


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billhuntersemail(at)gmail
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PostPosted: Wed Jun 13, 2018 11:23 am    Post subject: Sequence for bringing alternators on line. Reply with quote

Thanks!!!

Bill Hunter




From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert L. Nuckolls, III
Sent: Wednesday, June 13, 2018 9:01 AM
To: aeroelectric-list(at)matronics.com
Subject: Re: Sequence for bringing alternators on line.

At 10:29 AM 6/13/2018, you wrote:

Quote:

Regarding the SD 20, does anybody know what its output should at 1,000 RPM (engine idle) and also at 2400 RPM Cruise?

Thanks,

See https://goo.gl/m6i8qR

At engine 1000 rpm, alternator rpm is about 1300 . . .
you might see 5 or so amps.

At engine 2400, alternator 3,000 the chart
says 29A


Bob . . .


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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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