Re: 3 Coil System Was: A photographic tutorial of Pancake Coilwinding...with movies...(fwd)

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---------- Forwarded message ----------
Date: Sun, 24 Jun 2007 03:00:00 -0700
From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: 3 Coil System      Was: A photographic tutorial of Pancake
    Coilwinding...with movies...(fwd)

Hi Dave,

I said I would measure and get back to you. Here it is:

>>I believe the special result of the exact tuned combination flat spiral and
>>solenoid is exactly for the reason I stated.  There is no inductive coupling
>>at the center of a flat spiral because the magnetic field is completely out
>>of phase with the solenoid.  Therefore, there is no need for a transmission
>>line.
>>  
>>
> On paper? In my experience, the magnetic field lines of the flat coil 
> "will" intersect the solenoid and there will be inductive coupling. 
> Tell you what, I can measure this with my small closewound flat coil 
> and a 2" solenoid about 9" tall. I'll report back the coupling.

I measured Mutual Inductance (Lm) via pumping a stable current through 
the flat coil and measured the voltage inductively coupling the solenoid.

Flat Coil = 13.625" outer diameter, 24 awg, 2" inner diameter, 252 
turns, L measured = 10.37 mH.
Solenoid Coil = 1.6875" diameter, 9" height, 24 awg, 390 turns, L 
measured = 1.12 mH.

http://www.classictesla.com/flat/flat_sol_Lm.jpg

Flat Coil = 4.52 Amps
Solenoid Coil = 0.58 Volts

Lm = V/(w * I) = 0.58/(377 * 4.52) = 340.4 uH
k = Lm/sqrt(L1*L2) = 340.4uH/sqrt(10.37mH * 1.12mH) = 0.1

BTW, Javatc modeled 340.08 uH for Lm and a k of 0.1

I then connected the base of the solenoid to the inside turn of the flat 
coil and measured.
Flat Coil = 4.71 Amps
Solenoid Coil = 0.605 Volts
Lm = 340.7 uH and k = 0.1
As you can see, the connection makes no difference.

I then removed the solenoid coil and placed it 1 meter away from the 
flat coil. I kept it hooked up electrically the same. I measured 0 volts 
across the solenoid with the same current flow. This occurred because 
the coil was not inductively coupled as it was taken far away from the 
coils ability to inductively couple (removed from the flat coils 
magnetic field).

The definition of "inductive coupling" = "the transfer of energy from 
one circuit component to another through their shared magnetic field 
(mutual inductance)". Is your definition of inductive coupling something 
other than this?

Take care,
Bart