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circuit protection on contactors

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deej(at)deej.net
Guest

Posted: Thu May 29, 2014 7:11 pm Post subject: circuit protection on contactors

We generally put some form of circuit protection (fuse, breaker, etc) on 

most of our circuits, including the circuit to activate the starter 

contactor, but we usually do not put any type of protection on the 

circuit to activate the master contactor or E-bus contactor.



I am curious, why is this?



Thanks,



-Dj, in the middle of re-wiring for a panel upgrade



-- 

Dj Merrill - N1JOV - VP EAA Chapter 87

Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

Glastar Flyer N866RH - http://deej.net/glastar/

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sprocket(at)vx-aviation.c
Guest

Posted: Thu May 29, 2014 10:08 pm Post subject: circuit protection on contactors

The practice is to protect against wires shorting to ground. The circuit protection trips due to large fault current.



The master or e-bus contactor control wires operate by grounding the conductor with a switch.  The current in this circuit is limited by the resistance of the contactor coil, so it needs no protection.  A short on this wire may cause undesirable behaviour, but it won't melt or catch fire.



Vern



====================================================

Sent from my iThing. It is responsible for all gramma and typo terrors.



 	  Quote: 	
		   On May 29, 2014, at 8:09 PM, Dj Merrill <deej(at)deej.net> wrote:

 

 

 

 We generally put some form of circuit protection (fuse, breaker, etc) on most of our circuits, including the circuit to activate the starter contactor, but we usually do not put any type of protection on the circuit to activate the master contactor or E-bus contactor.

 

 I am curious, why is this?

 

 Thanks,

 

 -Dj, in the middle of re-wiring for a panel upgrade

 

 -- 

 Dj Merrill - N1JOV - VP EAA Chapter 87

 Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

 Glastar Flyer N866RH - http://deej.net/glastar/

- The Matronics AeroElectric-List Email Forum -

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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jluckey(at)pacbell.net
Guest

Posted: Fri May 30, 2014 8:28 am Post subject: circuit protection on contactors

I agree w/ everything that Vern said and add that this circuit is unique in that the length of the positive wire which provides power for the coil is usually very short - only an inch or two - from the big positive terminal to the little coil terminal on the relay/solenoid and that's why we can get away with no circuit protection.  This is not the case with almost all other circuits.

-Jeff



 

     On Thursday, May 29, 2014 11:21 PM, Sprocket <sprocket(at)vx-aviation.com> wrote:

  

  



 --> AeroElectric-List message posted by: Sprocket <sprocket(at)vx-aviation.com (sprocket(at)vx-aviation.com)>



The practice is to protect against wires shorting to ground. The circuit protection trips due to large fault current.



The master or e-bus contactor control wires operate by grounding the conductor with a switch.  The  current in this circuit is limited by the resistance of the contactor coil, so it needs no protection.  A short on this wire may cause undesirable behaviour, but it won't melt or catch fire.



Vern



===========================

Sent from my iThing. It is responsible for all gramma and typo terrors.



 	  Quote: 	
		   On May 29, 2014, at 8:09 PM, Dj Merrill <deej(at)deej.net (deej(at)deej.net)> wrote:

 

 --> AeroElectric-List message posted by: Dj Merrill <deej(at)deej.net (deej(at)deej.net)>

 

 We generally put some form of circuit protection (fuse, breaker, etc) on most of our circuits, including the circuit to activate the starter contactor, but we usually do not put any type of protection on the circuit to activate the master contactor or E-bus contactor.

 

 I am curious,  why is this?

 

 Thanks,

 

 -Dj, in the middle of re-wiring for a panel upgrade

 

 -- 

 Dj Merrill - N1JOV - VP EAA Chapter 87

 Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

 Glastar Flyer N866RH - http://deej.net/glastar/

 

 

 ectric-List"  target="_blank">http://www.matronics.com/Navigator?AeroElectric-Lista href="http://forums.matronics.com/" target="_blank">http://forums.mat                     &nbs//www.matronics.com/contribution" target="_blank">http://www.matronics.co==================


	




   

 

  

 

 [quote][b]

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deej(at)deej.net
Guest

Posted: Fri May 30, 2014 8:42 am Post subject: circuit protection on contactors

Thanks all, that makes sense!

       

       -Dj

       

       

       On 5/30/2014 12:27 PM, Jeff Luckey wrote:

     

     [quote]                

             I agree w/ everything that Vern said and add that this             circuit is unique in that the length of the positive wire             which provides power for the coil is usually very short -             only an inch or two - from the big positive terminal to the             little coil terminal on the relay/solenoid and that's why we             can get away with no circuit protection.  This is not the             case with almost all other circuits.

         

           

         -Jeff

           

         

           

         

                                                  On Thursday,                   May 29, 2014 11:21 PM, Sprocket                   <sprocket(at)vx-aviation.com> (sprocket(at)vx-aviation.com) wrote:

                  

               

               

               --> AeroElectric-List                 message posted by: Sprocket <sprocket(at)vx-aviation.com (sprocket(at)vx-aviation.com)>

                 

                 The practice is to protect against wires shorting to                 ground. The circuit protection trips due to large fault                 current.

                 

                 The master or e-bus contactor control wires operate by                 grounding the conductor with a switch.  The current in                 this circuit is limited by the resistance of the                 contactor coil, so it needs no protection.  A short on                 this wire may cause undesirable behaviour, but it won't                 melt or catch fire.

                 

                 Vern

               

             

           

         

       

     -- 

Dj Merrill - N1JOV - VP EAA Chapter 87

Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

Glastar Flyer N866RH - http://deej.net/glastar/



[b]

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RnJCurtis(at)charter.net
Guest

Posted: Fri May 30, 2014 9:35 am Post subject: circuit protection on contactors

I agree w/ everything that Vern said and add that this circuit is  unique in that the length of the positive wire which provides power for the coil  is usually very short - only an inch or two - from the big positive terminal to  the little coil terminal on the relay/solenoid and that's why we can get away  with no circuit protection.  This is not the case with almost all other  circuits.

 [quote]    	  Quote: 	
		       As a matter of fact most installations have no external      wire going from the Fat Battery terminal to the coil.  It is contained      inside the sealed contactor so there is no access to it.

      

     Roger

	
[b]

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