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Re: Primary Coil Topologies Part 2/2



tesla-at-grendel.objinc-dot-com On Fri, 15 Mar 1996 12:31:42 +0700, you
wrote:

>>From MSR7-at-PO.CWRU.EDU Fri Mar 15 07:18 MST 1996
[snip]

>  Saucer-Shaped Spiral Primary Coil Geometry                           
>  Primary coil inside diameter (inches)=      12.00                    
>  Primary coil outside diameter (inches)=      25.50                   
>  Number of primary coil turns =     9                                 
>  Last turn elevation in inches =       4.75                           
>  Wire diameter (inches)=      .3750                                   
>  Solenoidal secondary diameter (inches)=      8.00                    
>  Secondary height (inches)=      26.25                                
>  Number of secondary coil turns =  860                                
>  Secondary coil wire diameter (inches)=      .0285                    
>  Primary coil inductance in microhenries:           51.79             
>  Secondary coil inductance in microhenries:        39720.50           
>  Secondary coil capacitance in picofarads:     13.08                  
>                                                                       
>  Position is secondary coil bottom turn position in inches            
>  above bottom turn of primary coil                                    
>  M = mutual inductance in microhenries                                
>  K = coupling coefficient                                             
>            Position           M                K                      
>               .00          388.29            .271                     
>              1.00          347.99            .243                     
>              2.00          307.43            .214                     
>              3.00          268.97            .188                     
>              4.00          233.89            .163                     
>              5.00          202.68            .141                     
>              6.00          175.35            .122                     
>              7.00          151.70            .106                     
>              8.00          131.37            .092                     
> 
[snip]

>Comments?
>Regards,
>Mark S. Rzeszotarski, Ph.D.
>
>
Mark,
	Thank you for the analysis, I found it very timely because I
had just over coupled my secondary to my primary and had blown pits in
adjacent turns on the secondary.

I just finished building a roll-arround cart for my coil. So given the
new setup, I did some basic measurements.

Primary:
	15.5 turns on a 30 degree cone.
	11.75" inside diameter
	31"      outside diameter
	5.75" height
	Rdc	41.8 milli ohms
	1/4" copper tubing

new data:	132 micro henrys	30" above driveway	

old data		124 micro henrys	16" above garage
floor.	
	(  note: I changed caps between these 2 measurements. So I'm
not sure if I gained 8 uH or if it just represents experimental error.
I blew my old 0.060" single layer polyethylene cap. 2 weeks ago.)

Secondary:

	2 polyethylene waste baskets glued large end to large end
giving a 7.5" to 8" to 7.5" diameter  with a 20" winding length.

	33.4 milli henrys
	13.5 pF self capacitance (app)

Toroid:

	28" x 4"
	30pF capacitance to ground. Oops, I didn't write down the
elevation from ground for this measurement, or for the secondary self
capacitance measurement either.
-------------------------------------------------------------------------------------------------------------

K measurement:

	I used the formula:	

	K = (1 - Ls/Lo)^0.5

	where Ls is the primary inductance  with the secondary shorted
and Lo is the primary inductance with the secondary open.

	I used my main cap, 11.4nF, as a resonating cap in parallel
with my primary, a 10K ohm resistor between my function generator and
the primary LC. 

	Lo =  7.7us => 131.7 uH

	Ls = 7.4us => 121.7 uH  with secondary even with the lower

                                                         primary turn.

	K = 0.276
-------------------------------------------------------------------------------------------------------------

1 " elevation of secondary

	Lo = 7.7us => 131.7 uH

	Ls = 7.5us => 125.0 uH	

	K = 0.226
-------------------------------------------------------------------------------------------------------------

2" elevation of secondary

	Lo = 7.7us => 131.7 uH

	Ls = 7.6us => 128.3 uH

	K = 0.160

at 3" elevation of the secondary I obtained the same readings as I did
at 2", so I stopped.

I hope that this helps with you computer model. I was please to obtain
results this close to the model given different primaries and using my
oscope as a frequency measurement device. I've got an LCR meter,
function generator and frequency counter "in the mail" so I'll be able
to make better measurements next week.

	jim