Re: [TCML] DRSSTC weird waveform behavior

[Michael Twieg <mdt24@xxxxxxxx>]

The "squiggles" on your output voltage are probably caused by a resonance
formed by your DC bus capacitors and their parasitic inductance, and the
parasitic inductance of the bus bars.  It can be pretty nasty, especially if
that resonant frequency is anywhere close to your drive frequency.

Also why do you think increasing the gate resistors will help with zero
crossing?  That will just slow the switching down, not speed it up.

-Mike

On Fri, Jul 1, 2011 at 6:01 PM, Justin B <boshjack@xxxxxxxxxxx> wrote:

>
> Hello, Recently been working on my DRSSTC seeing what my ZCS is.  Came to
> find I have large voltage spikes, and my switching is late.
>
> After getting tips and suggestions from Kizmo, I have moved the gate
> resistor from 5ohms to 10ohms, which killed my spike down a little.  Then
> also he told me Steve had a similar issue, and fixed it with a 20 ohm
> resistor. seen here (
> http://www.stevehv.4hv.org/DRSSTC2/waveforms/badoutput.JPG)  So im sure
> the simple fix to my overshoot is to do the same. Add resistors.  But what I
> want to know, What the heck is the deal with the high squiggles on the
> Output voltage? If i adjust the duty cycle to ONE more cycle, it mirrors
> over the horizontal.  1 more cycle, mirrors again.
>
> So, Here are my waveforms.
>
> With 5.1 ohm resistor on the gates
> http://i.imgur.com/pUJvR.jpg
> http://i.imgur.com/GlcAU.jpg
>
> with 10ohm resistor on the gates
> http://i.imgur.com/ZrfeX.jpg
> http://i.imgur.com/JMKIF.jpg
>
> But what the heck is this??
> http://i.imgur.com/nfcC7.jpg
>
> Any help is wonderful, Thanks =)
> --Justin B
>
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