Re: 2 layer primary puzzle

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Luc by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ludev-at-videotron.ca>

Hi James

A simple trick is to remember the left hand rule see:

http://www.tpub-dot-com/neets/book2/1b.htm

If the magnetic flux line flow in the same direction they add if
they are in opposite direction they canceled.

Cheers,

Luc Benard

Tesla list wrote:
> 
> Original poster: "James T by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<jamest2000-at-att-dot-net>
> 
> Hi Everyone,
>  I will keep this brief. I am working on an 8" coil with a 2 layer primary.
> I have constructed the primary and
> it is not behaving as I expected. I measured the inductance of the primary
> by itself.
>   What happens is, I measure from the outside of the top coil to the inside
> and the inductance goes up as
> expected. Then I drop down to the bottom layer and measure from the
> top/outside to the bottom/turn, oops, the
> inductance goes down as I go out. The inductance of the bottom coil seems
> to cancel the inductance of the top
> coil. Please set me straight on this.
> 1.understanding/myth - the winding direction between the 2 coils is
irrelevant.
> 2. understanding/myth - the "mutual inductance" of the 2 coils increases
> inductance, not cancels out the
> others inductance.
> 3. 2 layer primary's are a practical approach. I seem to recall some posts
> on this, and it was considered
> reasonable. Brilliant to ask now that it is done!
> Any comments will help. Thanks,
>  James Cart