Re: secondary wire diameter

["Tesla list" <tesla@xxxxxxxxxx>]

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

Hi Dmitry,

On 16 Aug 2005, at 12:25, Tesla list wrote:

> Original poster: "Dmitry (father dest)" <dest@xxxxxxxxxxx>
>
> Hello Malcolm aka "all" :-D

I'll pull my head in if that's what you want.

>  > 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?
>
>  > 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.
>
> it`s strange - as i wrote before, while working in 3:4 mode losses
> shouldn`t be too high - you may have been working at 9:10 or
> something, or even at 11:12, that is coupling coefficient of that coil
> was about 0.105-0.087. i hope several polyethylene layers would allow
> me to have k=0.28, so i could decrease wire diameter 2 times more, but
> winding 3000 turns - nooo, thanks :-)

Never wound more than about 1800 turns on a resonator.

>  >  > 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?
>
>  > 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.
>
> that`s true - secondary inductance is needed only for increasing
> primary inductance, to decrease influence of sg losses. and as sg are
> different, or the same coil is used with different types of sg - there
> might not exist a unified optimum - or there`re some of them - each
> for its sg type?

Best answer I can give is that there are occasions when a simple
single unblown gap works well. Then there are others where some
degree of airflow through such a gap is required to stop power arcs
(in my experience such as it is the higher the unloaded Q of the
primary, the more strenuous the effort need to avoid power arcs if
the power source has a fairly low impedance). Then the same coil
might perform better again with a sync rotary (gap closes up while
firing). I've never particularly liked multi-section gaps and they've
never worked all that well for me but they have for others. I
wouldn't like to say its horses for courses but it sometimes works
out that way.

>  >  > 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.
>
> nobody wants to wind 10000 turns, so actually there`re probably no big
> difference what wire size to use - if sg quenches bad, energy is
> dissipated in the primary, if it acts good - energy would go for
> corona and rf emission, right? :-) but situation becomes interesting
> if one wants to get maximum from given secondary, ex. - having
> increased primary power until flashovers levels, we still can increase
> the power further - increasing bps for example, or to put a bigger
> toroid - what would happen then? at all - don`t you think that coils
> projected for sparks of 3..4 (and more) secondary lenghts just can`t
> have low bps - just for the voltage decreasing, coz the toroid with
> radius more than secondary height is not looks so pretty, right? i
> have the same problem now  - my toroid with 1.2m diameter looks ugly
> and it`s at 900kv at 100bps :-(

I've never been interested in going for sparklength = 3x seclength.
It's just not in my goalbook. Does looking pretty really matter? ;)
Most coils I've built are simply cobbled together from an array of
parts in a matter of minutes. In fact I have to do exactly that this
evening - I've been asked to build a display of sorts for the open
day here.
    Only two coils I built were designed to be finished items - not
exactly the most flexible way to go. I had to braze an extra primary
turn to one of them to retune after adding a larger terminal.
Suddenly I ran into quenching problems (Lp increased by 50%) and had
to use a carefully adjusted airflow in the gap.

>  >  >  LDPE - could i make the coil from it?
>
>  > If it's not black, it should be fine.
>
> i saw different colours - blue, white, yellow, why black is so bad -
> it contains graphite?

I understand so from others. I haven't been unfortunate enough to
have obtained any and wound a coil only to find out it was a bad
idea. Gaspipe really needs to be at least partially conductive.

Malcolm

>
> * If it's under 10Amps it's leakage current *
> :-D
>
>
>