# Re: K Factor & Mutual Inductance

```Subject:
Re: K Factor & Mutual Inductance
Date:
Sat, 5 Apr 1997 07:35:08 +0000
From:
"John H. Couture" <couturejh-at-worldnet.att-dot-net>
To:
Tesla List <tesla-at-pupman-dot-com>

At 05:24 AM 4/3/97 +0000, you wrote:
>Subject:
>        Re: K Factor & Mutual Inductance
>  Date:
>        Wed, 2 Apr 1997 18:01:13 -0800 (PST)
>  From:
>        "Edward V. Phillips" <ed-at-alumni.caltech.edu>
>    To:
>        tesla-at-pupman-dot-com
>
>
>" is found the K Factor can be found by the equation
>>           K Factor = Lm/(sqrt(LpLs))
>> where Lp and Ls are the inductances of the primary and secondary coils.
>
>That equation is good for any coil - air-cored, iron cored or
>whatever? There are no conditions stated by Terman or anyone else to
>my knowledge (except JHC perhaps ;)
>
>> Note that the K Factor or coupling is not only dependent on the physical
>> location of the coils but also on several other parameters such as
>> resonant
>> frequency, Q Factor, log decrement, etc.
>
>Where is the frequency dependence in that equation? Lp? Ls? M? k? I've
>not observed any frequency dependence in Lp or Ls from DC to TC
>frequencies in all the measurements I've done. So it must be in k or
>M, right? But what defines either of those? Is the number of flux
>linkages between two coils frequency dependent? Why?"
>        The coupling factor is independent of frequency, Q, etc.
>the definition is exact (for coils inductively coupled coils).
>Ed
>
---------------------------------------------------

Ed -

The TC parameters are tied together by the impedences.

K = Xm/sqrt(XpXs)     Xm = 6.283 FLm

Xp = 6.283 FLp        Xs = 6.283 FLs

Q = Xs/Rs = 6.283 FLs   etc.

When a change is made in a TC parameter the impedence changes which
affects many other parameter impedences in the JHCTES computer program.
The
changes are necesary because the program keeps the system in tune.
Otherwise
you would end up with a system that was not in tune after the change.

John Couture
>

```