[Prev][Next][Index][Thread]
Re: Primary Coil Topologies Part 2/2
-
To: tesla-at-grendel.objinc-dot-com
-
Subject: Re: Primary Coil Topologies Part 2/2
-
From: jim.fosse-at-bdt-dot-com (Jim Fosse)
-
Date: Sun, 17 Mar 1996 07:03:12 GMT
-
>Received: from bdt.bdt-dot-com (root-at-bdt-dot-com [140.174.173.10]) by uucp-1.csn-dot-net (8.6.12/8.6.12) with SMTP id AAA07643 for <tesla-at-grendel.objinc-dot-com>; Sun, 17 Mar 1996 00:05:13 -0700
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