From: "Terrell W. Fritz"
Date: Mon, 14 May 2001 22:20:21 -0600
Subject: [TSSP] Measured vs. Operating coil coupling?
Hi All,
I am wondering if the measured (at say 60Hz AC) primary to secondary
coupling is the same as the coupling an operating coil sees? What makes me
wonder if they are different is the current profile along the secondary at
60Hz AC may be different than the operating profile such as example 8 at:
http://www.abelian.demon.co.uk/tssp/pn1710/
Perhaps the 60Hz AC and operating secondary current profiles are very
close. However, if there is any difference, it seems like the coupling
would also be affected buy the different secondary current profiles in the
two cases. Perhaps there is a resonant or dynamic coupling coefficient
that is different from the low frequency steady state coupling? I imagine
they would not be too different at any rate, but the effect may be real...
The effect of the top toroid as a shorted turn came up on the Tesla list
and I copied it below for reference...
Cheers,
Terry
>From: "Terry Fritz"
>To: tesla@pupman.com
>Subject: Re: Toroid Eddy Current?
>Hi Ray,
>
>I think there are three factors at work that diminish the shorted turn
>effect for toroids.
>
>1. The coupling is not real high. I used MandKV31 (coupling calculation
>program*) to find the coupling for a 22 inch C-C toroid with an 8 inch cord
>that was 10 inches above a 30 inch long 10.25 Dia. secondary with 1000
>turns. The coupling was only 0.028.
>
>*
>http://hot-streamer.com/TeslaCoils/Programs/Programs.htm
>
>2. Toroids are not real good conductors. Corregated dryer pipe and other
>aluminum materials are faily resistive to RF currents. Not sure how much
>difference that makes but...
>
>3. There is not much current near the top of the coil. As Paul's TSSP
>project and my tests have shown.** Thus, there is not a lot of nearby
>current to couple to the toroid.
>
>**
>http://hot-streamer.com/TeslaCoils/MyPapers/NSVPI/NVSPI.htm
>http://www.abelian.demon.co.uk/tssp/pn1710/
>
>I think all three of these have some affect and add up to only a small Eddy
>current effect from the toroid. The actual numbers and all are a bit fuzzy
>but it could probably all be figured out with a fair amount of precision.
>
>Cheers,
>
> Terry
>
>
>At 09:58 PM 5/13/2001 -0700, you wrote:
>>Doesn't the toroid form a single shorted turn that would dampen the
>>secondary by lowering the Q? It seems that the toroid is close enough to the
>>secondary to have an effect. An interesting test could be performed if
>>someone had a working coil with an identical spare toroid. That spare toroid
>>could be cut with a band saw radially toward the center stopping couple of
>>inches from the middle. Probably 3 or 4 (maybe more) equally spaced cuts
>>would be adequate and maybe dabs of epoxy to stabilize the cuts. Then
>>install the modified toroid, retune the coil and compare the results with
>>the original toroid.
>>
>>Maybe I'm off base but I have never seen this discussed and if the Q of the
>>material for the secondary coil form matters, seems this just might.
>>
>>Ray
>>
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.