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SD-8 Alternator Question

 
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ron228rj(at)gmail.com
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PostPosted: Tue Jan 23, 2018 1:39 pm    Post subject: SD-8 Alternator Question Reply with quote

When I bought my plane, which has an SD-8 alternator as the primary power source, it came with an inline fuse on one of the two leads from the alternator.

The guy who installed it said it was an 8 amp alternator so he added a 10 amp inline fuse. But, I believe it provides 8 amps at 14 volts after regulation and the voltage where the fuse is installed is something like 20-25 volts AC. So, the max current there would probably be a bit less than 8 amps anyway, right?
Regardless, it has never blown, but I am wondering if it is even serving a useful purpose other than to increase the number of electrical connections in my plane?
Thanks,
Ron


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rene(at)felker.com
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PostPosted: Tue Jan 23, 2018 1:53 pm    Post subject: SD-8 Alternator Question Reply with quote

My chief engineer here at work always says the fuse is there to protect the wire….keeps the smoke in……not the equipment at the end.

I have the same setup on my standby and I think that is what they gave me in the kit.

Rene'
801-721-6080

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Ron Springer
Sent: Tuesday, January 23, 2018 2:37 PM
To: aeroelectric-list(at)matronics.com
Subject: SD-8 Alternator Question

When I bought my plane, which has an SD-8 alternator as the primary power source, it came with an inline fuse on one of the two leads from the alternator.

The guy who installed it said it was an 8 amp alternator so he added a 10 amp inline fuse. But, I believe it provides 8 amps at 14 volts after regulation and the voltage where the fuse is installed is something like 20-25 volts AC. So, the max current there would probably be a bit less than 8 amps anyway, right?

Regardless, it has never blown, but I am wondering if it is even serving a useful purpose other than to increase the number of electrical connections in my plane?

Thanks,

Ron


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Peter(at)sportingaero.com
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PostPosted: Tue Jan 23, 2018 2:44 pm    Post subject: SD-8 Alternator Question Reply with quote

See this wiring diagram – shows a 15 amp fuse.

http://www.bandc.aero/pdfs/504-500%20REV%20I.pdf

Peter

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Ron Springer
Sent: 23 January 2018 21:37
To: aeroelectric-list(at)matronics.com
Subject: SD-8 Alternator Question

When I bought my plane, which has an SD-8 alternator as the primary power source, it came with an inline fuse on one of the two leads from the alternator.

The guy who installed it said it was an 8 amp alternator so he added a 10 amp inline fuse. But, I believe it provides 8 amps at 14 volts after regulation and the voltage where the fuse is installed is something like 20-25 volts AC. So, the max current there would probably be a bit less than 8 amps anyway, right?

Regardless, it has never blown, but I am wondering if it is even serving a useful purpose other than to increase the number of electrical connections in my plane?

Thanks,

Ron


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ron228rj(at)gmail.com
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PostPosted: Tue Jan 23, 2018 2:56 pm    Post subject: SD-8 Alternator Question Reply with quote

Thanks! I didn't know that it was standard to include the fuse in one of the wires. The person I bought the plane from made it sound like it was his idea. The 10 amp size seems to work fine for the SD-8. The wiring diagram applies to three alternators, including ones that are larger than the SD-8, which is probably why it calls for the 15 amp fuse.
Ron

On Tue, Jan 23, 2018 at 5:43 PM, Peter Pengilly <Peter(at)sportingaero.com (Peter(at)sportingaero.com)> wrote:
Quote:

See this wiring diagram – shows a 15 amp fuse.
 
http://www.bandc.aero/pdfs/504-500%20REV%20I.pdf
 
Peter
 
From: owner-aeroelectric-list-server(at)matronics.com (owner-aeroelectric-list-server(at)matronics.com) [mailto:owner-aeroelectric-list-server(at)matronics.com (owner-aeroelectric-list-server(at)matronics.com)] On Behalf Of Ron Springer
Sent: 23 January 2018 21:37
To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)
Subject: SD-8 Alternator Question
 
When I bought my plane, which has an SD-8 alternator as the primary power source, it came with an inline fuse on one of the two leads from the alternator.

The guy who installed it said it was an 8 amp alternator so he added a 10 amp inline fuse. But, I believe it provides 8 amps at 14 volts after regulation and the voltage where the fuse is installed is something like 20-25 volts AC. So, the max current there would probably be a bit less than 8 amps anyway, right?

Regardless, it has never blown, but I am wondering if it is even serving a useful purpose other than to increase the number of electrical connections in my plane?

Thanks,

Ron


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ashleysc(at)broadstripe.n
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PostPosted: Tue Jan 23, 2018 5:26 pm    Post subject: SD-8 Alternator Question Reply with quote

Hi Peter;

Hi Ron;
The drawing shows a ten amp fuse for an SD-8 alternator.
Cheers! Stu.
From: "Peter Pengilly" <Peter(at)sportingaero.com>
To: aeroelectric-list(at)matronics.com
Sent: Tuesday, January 23, 2018 2:43:56 PM
Subject: RE: SD-8 Alternator Question

See this wiring diagram – shows a 15 amp fuse.

http://www.bandc.aero/pdfs/504-500%20REV%20I.pdf

Peter

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Ron Springer
Sent: 23 January 2018 21:37
To: aeroelectric-list(at)matronics.com
Subject: SD-8 Alternator Question

When I bought my plane, which has an SD-8 alternator as the primary power source, it came with an inline fuse on one of the two leads from the alternator.
The guy who installed it said it was an 8 amp alternator so he added a 10 amp inline fuse. But, I believe it provides 8 amps at 14 volts after regulation and the voltage where the fuse is installed is something like 20-25 volts AC. So, the max current there would probably be a bit less than 8 amps anyway, right?
Regardless, it has never blown, but I am wondering if it is even serving a useful purpose other than to increase the number of electrical connections in my plane?

Thanks,

Ron


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nuckolls.bob(at)aeroelect
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PostPosted: Tue Jan 23, 2018 6:06 pm    Post subject: SD-8 Alternator Question Reply with quote

At 03:37 PM 1/23/2018, you wrote:
Quote:
When I bought my plane, which has an SD-8 alternator as the primary power source, it came with an inline fuse on one of the two leads from the alternator.

The guy who installed it said it was an 8 amp alternator so he added a 10 amp inline fuse. But, I believe it provides 8 amps at 14 volts after regulation and the voltage where the fuse is installed is something like 20-25 volts AC. So, the max current there would probably be a bit less than 8 amps anyway, right?

Regardless, it has never blown, but I am wondering if it is even serving a useful purpose other than to increase the number of electrical connections in my plane?


The SD-8, under some conditions, is capable of 10A
of output. A fuse should be sized for at least 1.5
times the expected continuous load . . . 2x or
3x is not unreasonable giving the very fast action
of a fuse versus circuit breaker.

If the SD-8 feeder is 14AWG or larger, a 20A
fuse is the better choice . . . 30A would not
be out of line.





Bob . . .


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Airdog77



Joined: 24 Nov 2013
Posts: 79
Location: Northern Virginia

PostPosted: Wed Jan 24, 2018 7:06 am    Post subject: Re: SD-8 Alternator Question Reply with quote

Bob,

I believe you're referring to the fuse on the main connection to the battery contactor from the S704-1 relay?

And Stu is referring to the SD-8 connection to the power bus, not the inline fuse depicted on one of the two alternator leads shown on the B&C diagram.

I too have questions on whether this 15A fuse should be included, but figured since Bob depicts it twice without it --both in the Z-13/8 and Z-25 diagrams that include a bridge rectifier (that B&C doesn't) for self excitation-- then it wasn't required.

Bob, can you confirm whether the 15A fuse at the actual SD-8 alternator feed is required or not if the self-excitation feature is employed?

Regards,
Wade


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Wade Parton
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PostPosted: Wed Jan 24, 2018 4:30 pm    Post subject: SD-8 Alternator Question Reply with quote

At 09:06 AM 1/24/2018, you wrote:
Quote:
--> AeroElectric-List message posted by: "Airdog77" <Airdog77(at)gmail.com>

Bob,

I believe you're referring to the fuse on the main connection to the battery contactor from the S704-1 relay?

And Stu is referring to the SD-8 connection to the power bus, not the inline fuse depicted on one of the two alternator leads shown on the B&C diagram.

I too have questions on whether this 15A fuse should be included, but figured since Bob depicts it twice without it --both in the Z-13/8 and Z-25 diagrams that include a bridge rectifier (that B&C doesn't) for self excitation-- then it wasn't required.

Bob, can you confirm whether the 15A fuse at the actual SD-8 alternator feed is required or not if the self excitation feature is employed?

Good eye! I'd forgotten about that fuse being
added some years ago. It's a good idea. One of
the failure modes for the rectifier/regulator
places a dead short on the SD-8 output. The fuse
keeps the dynamo from smoking. The RMS current
flowing out of the dynamo is about the same as
the DC output current from the rectifier/regulator.

This is a duty-cycle switched series regulator
with no energy-storage . . .



Bob . . .


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Airdog77



Joined: 24 Nov 2013
Posts: 79
Location: Northern Virginia

PostPosted: Wed Jan 24, 2018 6:06 pm    Post subject: Re: SD-8 Alternator Question Reply with quote

Bob,

Thanks for confirming that fuse should be installed. I literally just bolted my SD-8 to the vacuum pad during my engine build yesterday, so now I'll plan on adding back in that inline fuse.

Ron- Thanks for asking the question.... perfect timing!

Regards,
Wade


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PostPosted: Wed Jan 24, 2018 8:07 pm    Post subject: SD-8 Alternator Question Reply with quote

No problem. Thanks Bob!
Ron

On Wed, Jan 24, 2018 at 9:06 PM, Airdog77 <Airdog77(at)gmail.com (Airdog77(at)gmail.com)> wrote:
Quote:
--> AeroElectric-List message posted by: "Airdog77" <Airdog77(at)gmail.com (Airdog77(at)gmail.com)>

Bob,

Thanks for confirming that fuse should be installed.  I literally just bolted my SD-8 to the vacuum pad during my engine build yesterday, so now I'll plan on adding back in that inline fuse.

Ron- Thanks for asking the question.... perfect timing!

Regards,
Wade

--------
Airdog
Wade Parton
Building Long-EZ N916WP
www.longezpush.com



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