Re: free standing coil
Subject: Re: free standing coil
Date: Thu, 12 Oct 1995 22:24:40 -0400 (EDT)
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Ed, thanks for the comments.
> On the practical side of the Q issue, I asked Richard Hull about
> the Q's they get for their Magnifiers. He estimated that the loaded (
> meaning with terminal connected ) coil Q was about 80. This is probably
M>I define loaded Q in the classic sense of having the coil loaded
M>(in this case by spark resistance). In a normal use of a transmission
Uhm, OK, all I meant was the Q of a coil with a terminal attached- no spark
M>line it is normally by its characteristic impedance. Spark loading
M>is rather less well defined than this (depends on spark current and
M>degree of spark channel ionization).
Yeah, and since Q is usually considered to be a "steady" state quantitiy,
it doesn't mean as much under the transient of a spark since there are many
more frequencies present in a pulse discharge. But it still gives an idea
of the losses in the coil...
M>L/C ratio is the definitive factor in his Q measurement. The coil
M>former will add to R in the equation below as will spark when run-
R also differs due to skin and proximity effects in the coil wire itself and
eddy currents induced in its environment.
M>(Q=1/R x SQRT(L/C)
M>Characteristic impedance approx SQRT(L/C) for high Q coil
> since they used a fairly thick (1/4"?)1ft diameter PVC form, but they still
> get 100+ inch arcs at 7kW of input power. So, perhaps it is not worth
> the investment to obtain the highest Q's?!?
M>It would be an interesting exercise, but since the primary will be
M>the determining factor when powered, you're probably right. System
M>(coupled) Q is an aggregate : Qsys = SQRT(Qp x Qs)
> A related request for the group:
M>No problem. I'll post some data directly to avoid clogging the list.
M>I'll try and get it together this weekend.
M>I once tried the same trick on usa-tesla and got no help at all :-(
> The method I use to determine Q is the 1/2 power bandwith method: