Re: DRSSTC driver tests- Dual resonance disaster

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Steve Ward <steve.ward@xxxxxxxxx>

Jason,

I noticed this too!!  Guess what... its probably your scope getting
messed up by the magnetic fields produced by the coil.  Try moving
your scope around, try it on its side, etc.  I saw this happen once on
my BIG coil, because the scope (and myself) were huddled at the base
of the coil, about 2' from that big primary coil pulsing 100A or so,
and man the waveforms looked really bad (duty cycle looked to be 30/70
), then i moved the scope back and the problem dissappeared :).

I would be quite surprised if the duty cycle was really noticably off
in real life.  I dont think a TL494 will be any more stable than the
4046's VCO.

Steve


On Thu, 27 Jan 2005 16:18:31 -0700, Tesla list <tesla@xxxxxxxxxx> wrote:
> Original poster: "Jason Judd" <JJudd@xxxxxxxxxxxxxxxx>
>
> I have just noticed on my DRSSTC that with the PLL disabled (used only
> as an oscillator) the duty cycle changes through the burst making the
> IGBTs switch as non zero timmings. This only happens with the secondary
> in place and I suspect it is the field from the secondary/toroid causing
> the problem. At first I thought is was an interaction between the
> primary and secondary so I lowered the coupling, to around .1 , but that
> didn't change anything.
>
> I am going to try a TL494 to see if that is any more stable.
>
> Jason.