Re: secondary wire diameter

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

Hi Dmitry,

On 14 Aug 2005, at 12:44, Tesla list wrote:

> Original poster: "Dmitry (father dest)" <dest@xxxxxxxxxxx>
>
> hello all.
>
> how do you choose secondary wire diameter?

It depends on what I'm after. I have a personal guideline for both
close and spacewound secondaries which you'll find mentioned a few
times in the archives. That's if I'm after a reasonably high Q coil
which in my experience always works well. I've found performance for
Q's below 100 to be questionable and one coil I wound which had a Q
of 40 to be worth little more than scrap copper.

> imagine we have a certain secondary coil form, coil winding lenght -
> 1m. it`s known - "the more inductance - the better" - ok, but at very
> high number of turns the Q of the coil is decreasing. what minimum Q
> value could we use on practice? while my proto secondary working in
> 3:4 mode and Q=382, losses are 1.5%, at Q=100 they are 5.6%, at Q=50 -
> 11% (calculations results from Antonio`s "optesla"). as i`m going to
> choose minimum wire diameter, you may forget about skin-effect.

There is an optimum for a given coilform. Quantifying that optimum
exactly is not something I think has been done to date. The thing
about high inductance has more to do with reducing primary losses
than secondary ones. Primary losses are always higher in my
experience.

> how does the power of the coil is connected with the wire diameter -
> for example, what wire should we use at 2-4kw?

I just choose the coil length for some maximum output voltage, go for
an h/d ratio in the 3 - 5 region and wind either for high inductance
and moderate Q or more moderate inductance and higher Q.

 is it useful to wind
> the bottom of the secondary by more thick wire as the main current
> flows only there?

I wouldn't. Too much hassle. Besides, it reduces the coupling for a
given primary configuration.

> p.s.
> i`ve found the source of PE pipes with 10-300mm diameter and wall
> thickness of 2-28mm, but it`s LDPE - could i make the coil from it?

If it's not black, it should be fine.

Malcolm