Re: Shrink wrapped secondaries

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Paul,

Thanks for checking this! ;-)  It appears the shrink wrap has no real
affect on the coil.  I really like it, it is very easy to put on and
provides excellent protection to the coil.  It is also easy to take back
off if one wants.  I am gong to just leave it on the small coil.

I made no attempt to set the coil up on a nice ground plain or in a free
space area, so the surroundings were certainly affecting the coil.
However, I was very careful to have the coil in the exact same place and
not disturb anything so the before and after situation would be as close as
possible.  So just a before and after wrapping test rather than a greater
global test.  I am very sure the shrink wrap does not squeeze the coil to
any perceptible degree.  It is far far looser than the windings and is
really not that tight at all.  It is much like plastic food wrap.  In fact
it "is" just plastic food wrap that is thicker.

I am surprised you models were so close to the frequencies here.  Better
than 5%!!  Here is a picture of the test setup:

http://hot-streamer-dot-com/temp/P9070009.jpg

Not exactly "free space" ;-))

This morning I moved some of the boxes and such out of the way and repinged it:

http://hot-streamer-dot-com/temp/P9070010.jpg

http://hot-streamer-dot-com/temp/02090701.gif

http://hot-streamer-dot-com/temp/02090701.CSV

Subtracting the scope pics shows DC level shift from the cold scopes input
but some harmonics changed to in the "bumpy" parts in the beginning:

http://hot-streamer-dot-com/temp/02090702.gif

I should have tried it before I moved to boxes to see if anything shifted
overnight (like the cold scope, pinger, humidity...  and those little green
elves...) but I guess that would just raise even more questions ;o))

Cheers,

	Terry


At 04:43 PM 9/7/2002 +0100, you wrote:
>Terry wrote:
>
>> Without the shrink wrap, the ringdown looks like this:
>> http://hot-streamer-dot-com/temp/02090602.gif
>> http://hot-streamer-dot-com/temp/02090602.CSV
>
>> With the shrink wrap it looks like this:
>> http://hot-streamer-dot-com/temp/02090603.gif
>> http://hot-streamer-dot-com/temp/02090603.CSV
>
>Very nice recordings. The FTs look lovely,
>
>http://www.abelian.demon.co.uk/tmp/02.ft.gif
>
>for the unwrapped coil. The first six resonant modes show up very
>nicely.  A few more are visible but not big enough to take numbers
>from.  tcma reports 
>
>Unwrapped 02090602.CSV:
> PK  FREQ kHz (Error +/-)    Q FACTOR (Error +/-)   LEVEL
>  1  351.155 (0.01%,38Hz)     275.08 (0.17%, 0.5)  -0.3dB
>  2  872.170 (0.01%,95Hz)     249.82 (1.66%, 4.1)  -13.9dB
>  3 1263.176 (0.01%,137Hz)    190.67 (1.66%, 3.2)  -21.2dB
>  4 1598.179 (0.01%,173Hz)    146.37 (5.58%, 8.2)  -25.5dB
>  5 1904.784 (0.01%,207Hz)    117.08 (13.28%,15.5) -29.3dB
>  6 2198.208 (0.01%,239Hz)     95.24 (26.56%,25.3) -28.3dB
> 
>Wrapped 02090603.CSV:
> PK  FREQ kHz (Error +/-)    Q FACTOR (Error +/-)   LEVEL
>  1  351.160 (0.01%,40Hz)     275.08 (0.17%, 0.5)  -0.3dB
>  2  874.085 (0.01%,98Hz)     251.05 (1.66%, 4.2)  -13.8dB
>  3 1266.090 (0.01%,143Hz)    192.48 (2.35%, 4.5)  -21.2dB
>  4 1601.364 (0.01%,180Hz)    147.36 (5.58%, 8.2)  -25.4dB
>  5 1908.704 (0.01%,215Hz)    117.24 (13.28%,15.6) -28.7dB
>  6 2204.296 (0.01%,248Hz)     96.10 (26.56%,25.5) -27.2dB
>
>No change to f1 or q1.  The higher modes frequencies and q factors
>have gone up a little - opposite to what we'd expect.  
>
>I recognise this test coil, here is the comparison between your pings
>and the tssp model.
>
>     Measured   Modeled   Error
>f1     351.2     356.6    +1.5%
>f3     874.1     878.7    +0.5% 
>f5    1266.1    1282.5    +1.3%
>f7    1601.4    1626.2    +1.5%
>f9    1908.7    1983.5    +3.9%
>f11   2204.3    2303.7    +4.5%
>
>The large error at f1 is probably because I don't know where your
>coil is set up.  The increasing trend in error above f3 is due to the
>model not taking account of the coil former material, and this causes
>an error determining internal capacitance which increases with the
>mode number.  This trend shows up very nicely and demonstrates the
>benefit of pinging the coil to get a true picture of its mode spectrum.
>
>Wonder why the frequencies and Q factors went up?  If ambient
>temperature was involved, wouldn't all the Q factors change more or
>less in proportion?  We would expect q1 at least to vary some 0.5%
>per degree C.  Why does q3 go up nearly 1% and q1 stays put?
>
>More curious still is the frequency change of the higher modes.  
>Having gone the wrong way in the first place, why are the highest
>modes affected most, trending towards a +0.3% shift in frequency.
>If I see this pattern of error when modeling, it usually points to
>an error in measuring coil diameter.  Has your shrink wrap compressed
>the middle of the coil, reducing its diameter by about 0.5%?
>The gain in frequency would go some way to accounting for the gain
>in q.
>
>One thing's for sure, you haven't upset the coil's resonant properties
>by wrapping it, although you've managed to add a couple more mysteries
>to the growing pile.
>--
>Paul Nicholson
>--
>