Re: [TCML] DRSSTC CM600 Ringing

[Tyler <tyler.c.c@xxxxxxxxx>]

Well, I always like to not have any ringing above the threshold of the TVS
diodes, which this will likely hit around 600V on the bridge. These photos
were taken at a bridge voltage of 50VDC. Maybe it will get better as the
voltage goes up, if the problem is just that the current feedback signal is
too low for reliable input to the comparator, although that does not appear
to be the cause of this.

Good to know this sort of wave works fine for your coil. I'll give it a shot
at higher voltage and see how it goes.

Tyler


On Thu, May 12, 2011 at 9:13 AM, Phillip Slawinski <pslawinski@xxxxxxxxx>wrote:

> Hi Tyler,
>
> The scope shots you posted here don't look bad.  Any reason why you're
> worried about the ringing?  What voltage are you running the bridge at in
> those scope shots?
>
> In the photo of your H-bridge it looks like you left quite a bit of extra
> lead on the decoupling capacitor.  It may not matter much, but ideally you
> want the lead length to be as short as possible.
>
> I use a similar phase lead controller in my small coils, and I always get a
> little bit of ringing on the first one or two cycles.
>
> See here:
> http://www.flickr.com/photos/pslawinski/4168411736/
> http://www.flickr.com/photos/pslawinski/4482915060/
>
> The ringing doesn't stop me from making sparks.
> http://www.flickr.com/photos/pslawinski/4550187194/
>
>
>
> On Wed, May 11, 2011 at 22:15, Tyler <tyler.c.c@xxxxxxxxx> wrote:
>
> > I just recently finished rebuilding my coil with a new bridge built with
> > CM600's, and a new controller that is fed by the hammertone prediktor
> phase
> > lead.
> >
> > It is doing well, and can be adjusted for (almost) no ringing with the
> > timing adjustments, definitely much less ringing than my previous
> designs.
> > The problem is the first few cycles, no matter what I do I can't get rid
> of
> > the ringing. No adjustment removes it, and I've never had a design that
> > lacks this ringing.
> >
> > Can be seen in this scope shot (the horizontal line at the top of the
> > waveform is the DC bus voltage):
> > http://ctyler.scripts.mit.edu/IMG_0027.JPG
> >
> > Zoomed in here: http://ctyler.scripts.mit.edu/IMG_0030.JPG
> >
> >
> > The only solution I've come up with that helped, but did not eliminate
> the
> > problem, was putting in a big 25uF 1kv film capacitor directly across the
> > rails at the IGBTs, which can be seen in my bridge photo:
> > http://ctyler.scripts.mit.edu/IMG_0034.JPG
> >
> > Additionally, there seems to be a bit of extra ringing after the bridge
> > turns off and the energy in the primary is going down, although it's
> > possible this will go away when the secondary is in place?
> >
> >
> > I've looked around quite a bit and haven't found a reliable solution to
> > this
> > problem, which is noted in a number of places. Has anyone found anything
> > that helps out with this?
> >
> > Tyler
> > _______________________________________________
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> >
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