Re: [TCML] DRSSTC CM600 Ringing

[Eric Goodchild <ericgoodchild@xxxxxxxxx>]

Something else you may want to consider (not so much that it's related to
ringing) is add some more bus C as your inverter is really running out of
voltage at the middle and end of the burst.

Just thought I would add that.

Good luck,
Eric

On Thu, May 12, 2011 at 9:03 AM, Tyler <tyler.c.c@xxxxxxxxx> wrote:

> 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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> >
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