Re: Some new DRSSTC numbers

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Paul Benham" <paulb@xxxxxxxxxxxxxxxxxxxx>

Hi Steve,

So is the best efficiency is seen when the burst is just long enough to
ensure breakout?  So does the toroid size then set the length of spark
achieved if the burst length is adjusted accordingly?

Is the ring up time to breakout just set by the coupling factor and toroid
size or is there more to this eg input voltage?  It would be interesting to
see if the primary current ringup is faster with higher voltages or lower
primary resistance.

Cheers,

Paul.

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Thursday, January 20, 2005 3:03 PM
Subject: Some new DRSSTC numbers


> Original poster: Steve Ward <steve.ward@xxxxxxxxx>
>
> Might interest the DRSSTC folks...
>
> I recently rebuilt my very first DRSSTC:
>
> http://www.stevehv.4hv.org/DRSSTC1.htm
>
> I recorded some numbers and made some interesting discoveries.
> Numbers are posted on the webpage at the bottom.  Seems my setup is
> really starting become *quite* efficient.  60" vertical arcs were
> achieved at only 800W of real power into the coil (PF is about .83 for
> my setup!), and this is mainly limited by my space, i could probably
> get about 66" or so. Im working on getting a current transformer so i
> can monitor the primary current accurately as this is very important
> to gain further insight on things.
>
> I feel i have some reasons to back up the coil's increase in performance.
>
> 1) new secondary with a higher Q (that is, lower winding resistance).
> Also, it is larger, allowing for longer sparks before any racing
> sparks.  Old secondary: 4.5"x19" 30awg magwire.  New secondary:
> 6.5"x22" 26awg magwire.
>
> 2) higher coupling between primary and secondary (went from .25 to .3).
>
> 3) lower tank impedance.  Started out with a 75nF cap and 20uH primary
> inductance, now im running a 300nF cap and 10uH of inductance.
>
> 4) due to implications of #3 (faster ring up achieved) i only require
> about 100uS to achieve excellent results (i think Dan M's coil uses
> around 300uS!).  Longer burst lengths result in much poorer efficiency
> (see table on website).
>
> The thing that really hurts my "experiment" is that I didnt take down
> these numbers for the original setup for a "direct" comparison.  But i
> knew the older setup well, and i will say that i never achieved
> efficiencies quite this high!
>
> I have 4 working DRSSTCs and haven't killed an IGBT since... hmmmm,
> well i cant remember ;-)))) (several months now).  Must be getting
> closer ;-).  Just takes some design revisions and lots of
> perserverence to get a reliable DRSSTC (or 4!) that kick(s) out some
> super sparks.
>
> Seeya,
>
> Steve
>
>
>
>
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