Re: Pentode TC - progress (fwd)

---------- Forwarded message ----------
Date: Mon, 27 Jul 1998 12:54:38 EDT
From: FutureT-at-aol-dot-com
To: tesla-at-pupman-dot-com
Subject: Re: Pentode TC - progress (fwd)


Fr. Tom M. has suggested that the heating of the toroid is
due to dielectric heating of the air surrounding the toroid.  A 3" by
11" toroid installed on my (33" spark) tube coil also got quite warm.

John Freau

In a message dated 98-07-26 22:44:14 EDT, you write:

 3. The topload, an 8" x 3" toroid, got very warm on its underside within
 about 30s of running. This suggests that eddy current heating is
 significant. The topload was made from the usual aluminium flexible hose,
 with the ridges/valleys evened out using polyester filler. This was then
 sprayed with Ni shielding spray before being given an aluminium foil tape
 Remembering that heating effects are due to the rms values, it is easy to
 see that CW coils which develop high everage powers will cuase such heating,
 whereas spark-gap driven TCs tend to have lower average powers for the same
 input power. In those cases the heating effect is lessened.
 Point no. (3) above is interesting: I remember a couple of years ago when
 the issue of "shorted turn" toroids arose, the excellent debates that sprung
 up. I seem to remember that Greg Leyh used a slotted toroid on his 160kW
 system which he later felt wasn't necessary and did various experiments to
 show that the eddy current losses were small. Many people contributed to the
 debate and supported the conclusion that slotting the toroid was an
 overkill. Well, maybe after all it is necessary (for CW coils  but not spark
 gap driven ones).