Re: eddy current with secondary coil + SSTC +RF power

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

Original poster: "chris swinson" <exxos-at-cps-games.co.uk> 

HI Terry, all

I spent most of the day reading that stuff! the old brain went dead on the
math but made interesting reading.

After reading though some info on my website on the matter, it would seem
that a coil of 2000 turns of 0.2mm wire gave 1" output, the RF radiated was
small. The larger the coil the larger the RF effect ( why is that anyway
? ), Then I try my plastic wire coil which has 500 turns of 2.5mm2
multistrand wire and with the same input power gives the same 1" arc. Does
this mean this coil is actually better since it has 1500 less turns ?

I'm also wondering about the inductance of the coils also. My 0.2mm coil was
like120mH and the plastic coil was 5mH. On my SSTC the 0.2mm coil needed
50VDC input ( 50watts ) and the plastic wire coil needed 180VDC ( 50watts )
input for the same 2! arc output. Now the thing you have to ask yourself now
is it REALLY better or not ? With a higher voltage input then per-volt turns
must be higher which is probably why it gave the same output. Dont forget
50VDC input 2000 turns, and 180VDC input 500 turns, would seem that the end
voltage would be the same.

So here I see lower inductance needs a higher voltage input to work the
same. Proximity effect of the plastic wire coil must be less, surface area
is also larger so resistance should be less. In all the plastic wire coil
sounds a much higher Q. My question is "Is it really better ?" Same input
power, same output arc length. Though it seems a bit odd that if the Q of
the plastic coil is so much better, then in fact its not made any differance
at all ?!


In terms of RF power output, the larger dia wire works better than thinner.
I can only assume it is acting as a antenna of some kind ? If RF is
considered a loss out energy radiated by the coil then the small 0.2mm wire
coil should give better arc length than anyother coil, I found always that
larger wire gave stronger RF, though is this good or bad ? If this power is
radiated then is it wasted power which could have gone into the arc length
instead ?

AFAIK larger wire should be higher Q and give better results. Though at the
moment all larger wire does is radiate more RF.  I can only here guess that
the proximity effect is canceling this power out more on the smaller wire
coils. On the larger wire dia coils, inductance,resistance is less and this
must radiate more RF ? Or is it just coincidence ?

I hope someone has done something along these lines. Its very hard to
understand why RF power is more. I do want to maximize RF power is anyone
has got any ideas on this ? I'm not too interested in arc length in this
experiment.  Though it would interesting to find out why all coils give same
results even though larger wire dia coils should be higher Q and also give
more RF output, when IMO it should boost the arc length instead due to
higher Q.

Anyone clear all this up ?   Who would have thought winding a bit of wire on
a tube could be so involved ;-)

Chris


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, October 05, 2003 6:25 PM
Subject: Re: eddy current with secondary coil


 > Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>
 >
 > Hi Chris,
 >
 > I am note sure there is a "nice" program to do such things.
 >
 > Here are some papers which deal with this:
 >
 > http://engineering.dartmouth.edu/other/inductor/papers.shtml
 >
 > Go to the ones under Litz wire.
 >
 > All the papers under "Magnetics Design" are pertinent if one's brain can
 > comprehend them...
 >
 > Paul has done vast work in this area too:
 >
 > http://www.abelian.demon.co.uk/tssp/
 >
 > Finding the "Q" of a secondary is very messy:
 >
 > http://www.abelian.demon.co.uk/tssp/qvar070402/
 >
 > So far, there is no wonderful way to predict it with high accuracy.  It is
 > dramatically affected by too many obnoxious things...
 >
 > Cheers,
 >
 >          Terry
 >
 >
 >
 >
 > At 09:58 AM 10/5/2003, you wrote:
 > > > Low-frequency inductances and mutual inductances. Most of the
 > > > formulations that I used assume uniform current in the wires,
 > > > radially and along them.
 > > >
 > > > Skin and proximity effects have some effect on inductances, but
 > > > the most serious deviation from the DC values in this case is
 > > > caused by the capacitances of the coils changing the currents
 > > > along the wires. It's easy to take this into account, if the
 > > > current profiles are known, but this is not implemented in my
 > > > program yet. The program developed by Paul Nicholson (Acmi) can
 > > > take the current profiles into account.
 > > > Eventually I will look at this problem, but I would like to find
 > > > first a good method to calculate the current profiles.
 > > >
 > > > Antonio Carlos M. de Queiroz
 > > >
 > > >
 > >
 > >
 > >Is there a program which will calculate secondary coils with space
windings
 > >? and maybe even further do the math to work out various resistance and
 > >current effects of litz wire also ?
 > >
 > >Chris
 >
 >
 >
 >