[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Toroid's effect on Q of the secondary



Original poster: "Peter Terren" <pterren@xxxxxxxxxxxx>

The question of a slit toroid has been raised way back by the pioneers of toroids but experimental evidence did not show any difference. It was one of the first questions I asked this list when I joined originally some years ago. The toroid is generally kept sufficiently high above the secondary while still preventing any corona off the top turn.
Examples of getting it right are here: http://tesladownunder.com/Tesla_7ft.JPG
and getting it wrong here: http://tesladownunder.com/Tesla18inch1st2.JPG

Peter

Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>
Hi Norman,
I have not heard of anyone using a slit toroid. You may be experimenting into a topic that hasn't been looked into deeply. I generally keep my toroid as high as possible (not allowing sparks to issue from the top winding, well, unless I'm in a lazy mode of operation). It's been stated on the list that a toroid low or partially covering the top windings may heat the top windings (I have not experienced this myself). It certainly appears the Q was definitely affected. Out of curiosity, how did you measure fo?

Take care,
Bart

Tesla list wrote:

Original poster: norman@xxxxxxxxxxxxxxxxxxxxxxxxx
I just finished measuring the resonance frequency of my secondary by observing the null due to the series resonance of the 1/4 wavelength coil. The toroid on top of the coil was constructed out of 4", "semi-rigid flexible aluminum duct", bought in Home Depot. The ID is 3.5", OD 11.5" and the center of the toroid is hollow so that it slides over the PVC coil form. The coil is 9" x 3.5" wound
with # 24 wire and resonates at 500kHz.

I noticed that when the toroid was about 3" above the top of the secondary
winding the resonance notch was very deep, but when the toroid was moved close
to the top of the winding, the notch was not very steep.  Clearly the toroid
was affecting the Q of the coil, probably by acting as a shorted turn. I have not come across any information about how far the toroid should be placed from the top of the coil. Anybody have any information about this? Should I place
a slit through the toroid?

Also the surface of the semi-rigid flexible duct looks like an accordion with
1/4" deep ridges spaced about 1/4" apart.  Will this surface effect the
streamers?  This is a low power Tesla coil that I hope will produce at least
10" streamers.