Re: Winding vs Space-Charge Capacitance
From: Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: Sunday, November 02, 1997 3:23 PM
To: Tesla List
Subject: Re: Winding vs Space-Charge Capacitance
> From: terryf-at-verinet-dot-com[SMTP:terryf-at-verinet-dot-com]
> Sent: Saturday, November 01, 1997 4:44 PM
> To: tesla-at-pupman-dot-com
> Subject: Winding vs Space-Charge Capacitance
> Hi all,
> Testing I have done on secondary coils with no top toroid suggests that
> the secondary inductor's capacitance is composed of two main capacitances in
> parallel. The first capacitance is internal to the coil winding itself and
> is probably composed of turn-to-turn capacitance. The second capacitance is
> a large space-charge region that is developed around the top end of the
> coil. The first capacitance is in the order of 0.25 pF while the second
> capacitance is on the order of 6.3 pF.
> Coil length 29.0 inches
> Diameter 4.25 inches
> 1000 turns #30 wire
> Non-Linear (winding pitch proportional to cos(x))
> inductance 16.06 mH
> Fo 496.2 KHz (no top terminal)
> Rac ~108 ohms
> Q ~460
> Note: Rac and Q may be inaccurate (unproven test methods).
> If this is true than it would suggest a number of possibilities to optimize
> output voltage. I am surprised that the turn-to-turn capacitance is so low.
> This is one of my non-linear wound coils but if the turn-to-turn capacitance
> is this low, I should be concentrating on field patterns and forget the
> internal capacitances. I haven't cross-checked these results so I may have
> a measurement problem or something.
> Does anyone have any comments on these results or comments on the
> small turn-to-turn capacitances I seem to be seeing.
Your observations are exactly right. For most purposes, C turn-turn
can be disregarded. Why? Look up the coil : you see a whole lot of
capacitances between each wire and its neighbours and these are
shielded from other close turns up the same side of the coil. Each is