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Twisted Pairs, Coils, and EM Fields

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aeroclaw(at)yahoo.com
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Posted: Mon Apr 06, 2009 7:01 pm Post subject: Twisted Pairs, Coils, and EM Fields

Bob-

I recently bought an IVOPROP magnum inflight adjustable propeller; the adjustment is done with an electric motor.  The power and ground leads are both approximately 12 feet long, as are the two leads that go from the switch to the carbon brushes.  The installation directions explicitly state "Do not cut the wires"; I called IVOPROP and asked if that applied to all four wires, or only the ones going out to the prop.  They stated that all the wires should be left alone, as the resistance of the wires was part of the calculation for circuit breaker selection, and shorter wires would result in the breaker tripping  more easily.  So, I have two pair of 12 fort wires to stow in behind the panel of an RV-7.



I don't want simply to coil the wires out of concern for the EM field the coil would produce whenever I'm changing the pitch of the prop.  Can I take the power/ground pair and twist them, take the two leads out to the prop and twist them, then twist the two twisted pairs together, and finally stow them in a loose but well-secured coil?  Memories from college physics lead me to think the electrons flowing in opposite directions should cancel each others' fields, but those memories are a little hazy.



Thank you,

Gregory Clawson

RV-7, E-6/200, N687LC (res)





         [quote][b]

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nuckolls.bob(at)aeroelect
Guest

Posted: Mon Apr 06, 2009 8:40 pm Post subject: Twisted Pairs, Coils, and EM Fields

At 09:58 PM 4/6/2009, you wrote:



 	  Quote: 	
		  Bob-

I recently bought an IVOPROP magnum inflight adjustable propeller; 

the adjustment is done with an electric motor.  The power and ground 

leads are both approximately 12 feet long, as are the two leads that 

go from the switch to the carbon brushes.  The installation 

directions explicitly state "Do not cut the wires"; I called IVOPROP 

and asked if that applied to all four wires, or only the ones going 

out to the prop.  They stated that all the wires should be left 

alone, as the resistance of the wires was part of the calculation 

for circuit breaker selection, and shorter wires would result in the 

breaker tripping more easily.  So, I have two pair of 12 fort wires 

to stow in behind the panel of an RV-7.


	


    This borders on bizarre. I cannot imagine anbody

    figuring wire length into the sizing of a circuit

    breaker.

 	  Quote: 	
		  I don't want simply to coil the wires out of concern for the EM 

field the coil would produce whenever I'm changing the pitch of the 

prop.  Can I take the power/ground pair and twist them, take the two 

leads out to the prop and twist them, then twist the two twisted 

pairs together, and finally stow them in a loose but well-secured 

coil?  Memories from college physics lead me to think the electrons 

flowing in opposite directions should cancel each others' fields, 

but those memories are a little hazy.


	


    I'm pretty sure just running them in parallel

    bundles is fine. I've written the company to

    inquire as to the physics behind any determination

    of criticality for bundle length.



    Watch this space.

        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

        ----------------------------------------

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