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Current Limiter Question...

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idleup

Joined: 06 Aug 2011
Posts: 19

Posted: Mon Oct 22, 2012 1:32 pm Post subject: Current Limiter Question...

I am a bit confused and thought I would ask here for clarification. I am trying to design my electrical system from Z-13/8. It looks as though there is a  direct route for the power direct to the battery and if the wire from the master relay to the power buss shorts out the full current of the battery would flow with no circuit protection? should their be a current limiter between there? 



Also, it is not specified on the drawing, is this a 4AWG wire between the battery contactor and the main power bus?



Thanks,

Matt

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nuckolls.bob(at)aeroelect
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Posted: Mon Oct 22, 2012 7:13 pm Post subject: Current Limiter Question...

At 04:32 PM 10/22/2012, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "idleup" <matt(at)mattandmel.com>



 I am a bit confused and thought I would ask here for clarification. I am trying to design my electrical system from Z-13/8. It looks as though there is a  direct route for the power direct to the battery and if the wire from the master relay to the power buss shorts out the full current of the battery would flow with no circuit protection? should their be a current limiter between there? 	


   No. Those are "fat wire" feeders that have never benefited

   from circuit protection in light aircraft. 



   This philosophy is an echo of design goals for light aircraft

   as described in FAR23:



 Sec. 23.1357 Circuit protective devices.



         (a) Protective devices, such as fuses or circuit breakers, must be

         installed in all electrical circuits other than--

                  (1) Main circuits of starter motors used during starting only; and

                  (2) Circuits in which no hazard is presented by their omission.



         (b) A protective device for a circuit essential to flight safety may not be

         used to protect any other circuit.

         (c) Each resettable circuit protective device ("trip free" device in which

         the tripping mechanism cannot be overridden by the operating control) must be

         designed so that--

                  (1) A manual operation is required to restore service after tripping; and

                  (2) If an overload or circuit fault exists, the device will open the

                  circuit regardless of the position of the operating control.

         (d) If the ability to reset a circuit breaker or replace a fuse is

         essential to safety in flight, that circuit breaker or fuse must be so

         located and identified that it can be readily reset or replaced in flight.

         (e) For fuses identified as replaceable in flight--

                  (1) There must be one spare of each rating or 50 percent spare fuses of

                  each rating, whichever is greater; and

                  (2) The spare fuse(s) must be readily accessible to any required pilot.



 

  	  Quote: 	
		  Also, it is not specified on the drawing, is this a 4AWG wire between the battery contactor and the main power bus? 	


   How much current is going to flow in it? The z-figures

   are ARCHITECTURE drawings, not wiring diagrams. The wire

   sizes are selected in accordance with anticipated loads.

   4AWG is certainly large enough and wouldn't hurt but it

   could be smaller as dictated by a load analysis.



 

   Bob . . .    [quote][b]

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