Re: Modeling E-Fields of Tesla Coil - Building a model

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

Original poster: "Antonio Carlos M. de Queiroz" <acmdq-at-uol-dot-com.br> 

Tesla list wrote:
 >
 > Original poster: "Eastern Voltage Research Corporation" 
<dhmccauley-at-easternvoltageresearch-dot-com>
 >
 > I have ANSOFT's Maxwell 2D and 3D program which can do both magnetostatic
 > and electrostatic modeling.
 > Just had a few questions for how to properly model a tesla coil.
 >
 > SECONDARY COIL
 > *****************
 > Can I make the assumption that voltage is evenly distributed down the
 > secondary coil from the potential seen on the top load
 > to the ground plane (0V)?  If so, I would probably split the secondary into
 > a number of smaller disks and assign a potential for
 > each disk.

The actual voltage profile can be more complex, but a linear variation
is a good approximation.

 > FOR SINGLE TOROID
 > *******************
 > For a single toroid, i assume the entire toroid should be set at a single
 > voltage.

Surely.

 > FOR DOUBLE STACK TOROIDS
 > ****************************
 > How do you treat the potential across say two stacked toroids.  Do you
 > assume each toroid has equal potential ? ? ?

Yes.

 > BREAK-OUT POINTS
 > *******************
 > Should be easy enough by merely putting a small dib on the toroid.

Yes, but this breaks the symmetry, and a 3D simulation is required.

 > Any other thoughts or comments??

This simulation can predict the initial breakout voltage, and
calculate some capacitances. To predict the behavior of the system
before breakout, with more precision than a simple lumped model,
you would have to simulate inductances too, maybe by splitting the
coil as a series of coupled inductors across a network of capacitances,
that a simulator can calculate. The complete system could then be
reduced to a complicated lumped circuit and simulated in a
conventional circuit simulator. A more complete model would have
to include resistances, including skin effect and irradiation,
and even so the simulation would only predict what happens before
breakout. And I didn't mention a primary spark gap, if this is
an "old type" coil.

Antonio Carlos M. de Queiroz