Re: 2 layer primary puzzle

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hello James,
               It is obvious from your description of the problem 
that the winding direction of both layers is such that the layers are 
series-opposing. You will have to reverse the winding direction of 
one layer or reconnect the two so that the outer turn of one connects 
to the inner turn of the other. The winding direction does not matter 
thing relates to primary vs secondary.

Malcolm

 
On 25 Sep 2001, at 13:27, 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
> 
> 
> 
> 
>