RE: K Factor & Mutual Inductance

            RE: K Factor & Mutual Inductance
            Mon, 14 Apr 1997 08:42:29 +1200
            "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
            Wellington Polytechnic, NZ

Hello John,

>   From: 
>         "John H. Couture" <couturejh-at-worldnet.att-dot-net>
>     To: 
>         Tesla List <tesla-at-pupman-dot-com>
> At 03:33 PM 4/10/97 +0000, you wrote:
> >Subject: 
> >        RE: K Factor & Mutual Inductance
> >  Date: 
> >        Thu, 10 Apr 1997 07:54:36 -0400
> >  From: 
> >        Heinz Wahl <hwahl-at-jtc-campus.moric-dot-org>
> >    To: 
> >        "'Tesla List'" <tesla-at-pupman-dot-com>
> >
> >
> >John,
> >
> >        You state that the R is effective, not DC or AC. Why can't you
> >measure the R of the coil, calculate the XL, at the
> >expected frequency of operation, and use the result to find a ballpark
> >Q? Could you elaborate on effective R?
> >
> >Heinz
> >
> >>---------------------------------------------------------
>  Heinz -
>  When you say "measure the R of the coil" I ibelieve you mean the DC
> measurement. Many coilers calculate the Q factor as you describe and
> obtain
> Q factors in the hundreds and sometimes thousands. These high Q factors
> can
> not be verified by tests that are properly performed.
>  The best way to get the calculations and tests to agree is to build
> many
> different coils and test them for Q and XL. The effective R can then be
> found. You can then make a graph of the results that can be used in
> designs
> before anything is built.
> >>
>  The Q factor is important because it it should be optimum if the spark
> gap
> is to operate properly. Too great a Q factor will interfere with the
> spark
> duration. I do not know of anyone who has ever made these tests.

Please elaborate.
>  The true nature of the Q factor can be elusive as I show in the Tesla
> Coil

Q is the inverse of the dissipation factor of the circuit.

> Notebook.
> The Q factor is tied to the log decrement by a famous constant
> ratio (pi). The Q factor is also equal to 1.364 times the number of
> cycles
> to reduce to 10% amplitude. It is obvious that this has an effect on the
> spark gap firing. If this was better understook coilers would have less
> problems with their spark gaps.

Unfortunately the log decr. formula doesn't apply to circuits 
containing a spark gap (linear decrement). That also applies to the 
secondary when sparks are emitted.
    An explanation of your last two sentences would be most welcome.