Re: Big Primaries, Small Caps

[Terry Fritz <twftesla-at-uswest-dot-net>]

Hi Greg,

	As you lower the primary inductance, the primary current increases.
Assuming the loss in the gap is proportional to I^2R, the higher current
burns off the energy as heat more in a low inductance primary then a high
inductance one.  Low inductance primary circuits have to be made well to
minimize the loss and handle the higher current.  Large inductance
primaries can get away with much lossier construction.

As I look at coils with very large primary caps, the primary inductance
tends to be very small.  This creates very high currents and giant losses
that can eat a coil's power vastly reducing the power to the arc.  It is
sort of a balancing act between more stored energy on the primary cap and
greater losses due to low primary inductance and high primary current losses.

Cheers,

	Terry



At 12:24 PM 8/31/00 -0400, you wrote:
>Dear List,
>
>I'm curious about Tesla coils with large primaries and small tank caps.
>John Freau and others have articulated numerous times over the years that
>coils so designed have lower gap losses and longer sparks relative to coils
>using big tank caps and few primary turns.  I'm curious as to why this is
>so.  It seems to me that the bigger bang size delivered by a larger cap
>would thump the secondary harder, yielding longer sparks.
>
>Can someone in the know provide an explanation?  I'm not an engineer, but I
>am an experienced comm/nav technician, so I can grasp pretty deep concepts.
> However, a side trip into Calculus land will lose me pretty quickly.
>
>Best Regards,
>
>Gregory R. Hunter
>