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Same rating for fuses and circuit breakers?

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Oct 23, 2018 1:36 pm Post subject: Same rating for fuses and circuit breakers?

At 02:44 PM 10/23/2018, you wrote:

  	  Quote: 	
		  I'll jump in, because that's one of my pet peeves. First, the mfgr of a

 widget shouldn't be asking the end user to supply protection for their device.

 	


   Right on!



 

 

   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Oct 23, 2018 1:57 pm Post subject: Same rating for fuses and circuit breakers?

At 03:49 PM 10/23/2018, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: Kelly McMullen <kellym(at)aviating.com>



 I seem to recall there is a reason that ammeters call for a 1 amp fuse on each lead from the shunt. It certainly isn't for wire protection, maybe to protect the meter movement 	




   Yeah, first saw them do that on the 336/337 series

   airplanes at the Pawnee plant. That was the

   idea . . . but the fusing constant for a AGC1

   (then a 3AG1) was such that a 5A flow of current

   would take about 30 milliseconds to pop the fuse.

   That 1 mA meter movement would be in trouble

   a lot faster than that!



   Don't know  if anyone tested that decision

   in the lab. There were some 50mV instruments

   with lower resistance (maybe 10mA?). The

   1 ohm fuse has about 200 mOhms of resistance.

   Two fuses in series at 10 mA gives you a 4 mV

   drop at full scale . . . 



   But I don't think anyone really paid much

   attention to the readings anyhow . . . ammeters

   are not really useful flight instruments.



 

 

   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Wed Oct 24, 2018 4:46 am Post subject: Same rating for fuses and circuit breakers?

At 09:11 PM 10/23/2018, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: Dick Tasker <dick(at)thetaskerfamily.com>



 To use when you get to your destination when you troubleshoot the problem.



 Dick Tasker 	


   Yup . . . keep 'em in the toolbox.



 

 

   Bob . . .

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