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SD-8 Alternator Question

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ron228rj(at)gmail.com
Guest

Posted: Tue Jan 23, 2018 1:39 pm Post 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

rene(at)felker.com
Guest

Posted: Tue Jan 23, 2018 1:53 pm Post subject: SD-8 Alternator Question

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

Peter(at)sportingaero.com
Guest

Posted: Tue Jan 23, 2018 2:44 pm Post subject: 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

ron228rj(at)gmail.com
Guest

Posted: Tue Jan 23, 2018 2:56 pm Post subject: SD-8 Alternator Question

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

ashleysc(at)broadstripe.n
Guest

Posted: Tue Jan 23, 2018 5:26 pm Post subject: SD-8 Alternator Question

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

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Jan 23, 2018 6:06 pm Post subject: SD-8 Alternator Question

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 . . .

Airdog77

Joined: 24 Nov 2013
Posts: 80
Location: Northern Virginia

Posted: Wed Jan 24, 2018 7:06 am Post subject: Re: SD-8 Alternator Question

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

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

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Jan 24, 2018 4:30 pm Post subject: SD-8 Alternator Question

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 . . .

Airdog77

Joined: 24 Nov 2013
Posts: 80
Location: Northern Virginia

Posted: Wed Jan 24, 2018 6:06 pm Post subject: Re: SD-8 Alternator Question

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

ron228rj(at)gmail.com
Guest

Posted: Wed Jan 24, 2018 8:07 pm Post subject: SD-8 Alternator Question

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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