Re: Low Voltage Tesla Coils

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

Original poster: "Justin Hays by way of Terry Fritz <twftesla-at-qwest-dot-net>" <pyrotrons2000-at-yahoo-dot-com>

Hi Terry,

Very interesting. I like the idea of a low voltage, high current
setup vs. a very expensive 25kV IGBT array. One problem comes to mind
though, and that is, tesla coils need high *peak* currents to make
big sparks. BUT, SSTC's and VTTC's generally supply only tens of amps
into the primary, and they seem to work OK. There isn't much pulsed
current here at all, but it is applied at every single cycle
(continuous wave - CW) and it works.

With spark-gap (non-CW) coils, the extremely high capacitor voltage
forces large currents into the primary inductance FAST, and this is
probably why spark gap coils are so efficient (sparklength vs. VA).

To my main point: As the tank voltage goes down (from transformer,
etc.), peak current goes down. And beyond a certain limit (who
knows...), I think coil performance will begin to suffer, as peak
currents drop below some sort of threshold.

So I think that unless these low currents are supplied continuously
(CW), I don't think the IGBT -at- low voltage method will work.

I suppose it would be like running an SSTC at a very low frequency --
there would be little current flow into the primary because it
wouldn't be tuned. It it WAS tuned, it would be an SSTC and would
work.

** But, maybe the applied voltage (across the primary) could be held
on for even as long as a few tens microseconds, letting the current
build up to several hundred amps (have to calculate that...probably
way off) THEN release it, and let the field collapse into the
secondary and ring the heck out of it. Like an ignition coil.

Something to try, for sure.

Take care,

Justin Hays
KC5PNP
Email: justin-at-hvguy-dot-com
Website: www.hvguy-dot-com