[Prev][Next][Index][Thread]
Re: K Quiz
Subject: Re: K Quiz
Date: Tue, 10 Jun 1997 11:41:13 +1200
From: "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
Organization: Wellington Polytechnic, NZ
To: tesla-at-pupman-dot-com
Hello Mark, all,
Following on from Mark's little quiz, I have the
following query which might relate to something quite important
performance-wise.....
> Hello coilers,
> Here is a little food for thought.
> "K" is the term applied to the degree of magnetic coupling between
> the
> primary and secondary coils of a conventional tesla coil (or the primary
> and
> driver
> coil in the magnifier configuration). Typically, we aim for values
> between
> 0.1 and
> 0.25 or so for a conventional tesla coil, and 0.4 or higher for
> magnifier
> primary/driver coil systems. "M" is the amount of mutual inductance
> between the
> primary and secondary coil. We define:
> K = M / SQUARE_ROOT [ Lp x Ls ]
> where Lp is the primary inductance, Ls is the secondary inductance, M
> is the
> mutual inductance, and K is the coefficient of coupling between the two
> coils.
<snip of quiz>
k itself is relatively easy to measure and quantify. But as far
as I know, the figure says nothing about _how_ the primary is
coupling into the secondary. For example, I can score identical k's
with a flat primary with the same outer dimension as that of the
resonator when placed below the resonator as I can with a helical
primary with the resonator sitting inside it (easy). Has anybody
examined performance issues around the degree of coupling into say,
just the bottom few turns vs a primary that loosely couples a long
way up the secondary? I have a gut feeling that this may be a
significant determinant of system performance given the normal high
secondary Q's and the fact that all else being equal, performance
for a given power input varies so widely in different systems.
Malcolm