Re: Four Layer Coil

Subject:      Re: Four Layer Coil
       Date:  Mon, 16 Jun 1997 09:51:41 +1200
       From: "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
Organization: Wellington Polytechnic, NZ
         To:  tesla-at-pupman-dot-com

Re 4 layer coils:

> > We wound our first layer exactly as always.  The second layer over 
> > over the first - same direction.  You'll find that it is very 
> > important that there be NO gaps in the underlying layer or you will 
> > have problems with the next layer.  We did a total of four layers.  
> > Next, we soldered all four wires together.  In effect, the four coils 
> > are in parallel.
> It would see to me that placing the layers in parallel you would be 
> decreasing the inductance, ie.
>  Total I = 1 / (1/Ifirstlayer) + (1/Isecondlayer)...+(1/Inthlayer)
> Are you saying that even though it reduces the inductance it is still 
> a gain over using the equivelent larger gauge wire?

The coils are mutually coupled (k approaching 1). That is not the 
same as connecting separate inductors in parallel. In fact, Bert is
approaching the use of real litz wire.