LabCoatz Staccato QCW No straight sparks

[Admiral Aaron Ravensdale]

Hi new build, new issues :-(
I build the Staccato QCW out of this Video.

With the following stats.



and shematic


Now I run into the issue that I don't get straight sparks!
First I try it with a 28cm Toroid and 337kHz@15nf
and now with a 20cm Toroid and 378kHz @40nf
With an Probe in the air it looks like the ramp is very short but i can change the time like described from 1ms to 8 ms



also confirmed the 378kHz when I zoom in on the upper picture




also the Signal at the Pin "Int" of the shematic looks good





But you can see only wild sparking more like an DRSSTC than QCW
any ideas whats wrong?

Video with 200VAC and all pulse width
https://photos.app.goo.gl/t16hUAzQX47Hd1Gm6

[ZakW]

Hello,

You first probe waveform looks to be the issue. You have a sharp spike in the beginning instead of a ramp. That spike is going to cause arcs to branch a lot. Are you powering the coil with unfiltered rectified AC (no bulk capacitors to smooth input voltage)?

The zero cross detector might not be triggering at the zero crossing, here is an example of that: When the coil turns on too late into the AC half cycle (ramp) it causes more of a burst of power into the primary rather than a more gradual ramp. What AC source are you using for the ZCD? In the picture, the purple trace is the probe hanging in air. Yellow is from an AC transformer.




This is the wave form you are looking for: Blue is the probe hanging in the air by the coil. Coil turns on at or as close to zero crossing and ramps up as AC voltage increases.


The 1-8ms adjustment determines when the coil shuts off. It should always trigger as close to the start of the AC half cycle (zero crossing) and then can be adjusted to shut off before the cycle has ended.

Good luck!

[Admiral Aaron Ravensdale]

Thanks for the reply.


You first probe waveform looks to be the issue. You have a sharp spike in the beginning instead of a ramp. That spike is going to cause arcs to branch a lot. Are you powering the coil with unfiltered rectified AC (no bulk capacitors to smooth input voltage)?

The side of the Power Input for the IGBT looks like that 2 Caps 250V 1000uf in series and a 1600V 100A Brick rectifier
 [ Invalid Attachment ]
The zero cross detector might not be triggering at the zero crossing, here is an example of that: When the coil turns on too late into the AC half cycle (ramp) it causes more of a burst of power into the primary rather than a more gradual ramp. What AC source are you using for the ZCD? In the picture, the purple trace is the probe hanging in air. Yellow is from an AC transformer.
I use this transformer 12.6V AC
 [ Invalid Attachment ]


This is the wave form you are looking for: Blue is the probe hanging in the air by the coil. Coil turns on at or as close to zero crossing and ramps up as AC voltage increases.

OK this looks quiet different.
How can I figure out if the which side cause the issue?

THANKS!

[ZakW]

The side of the Power Input for the IGBT looks like that 2 Caps 250V 1000uf in series and a 1600V 100A Brick rectifier

That is the issue. Just remove those capacitors and you should be good to go.

Since this is a ramped coil, you are trying to utilize the AC input (sine wave) ramp shape. With the filtering capacitors you are effective getting rid of that and smoothing it all out. So the coil is getting a high voltage pulse at startup.

The only other thing that you might need to verify is that the zero cross AC transformer is in phase with the AC bridge input. If you dont get any arcs after removing the filtering caps, try reversing the zero crossing transformer input.

nice build btw, those are some hefty resonant capacitors!

[Admiral Aaron Ravensdale]

The side of the Power Input for the IGBT looks like that 2 Caps 250V 1000uf in series and a 1600V 100A Brick rectifier

That is the issue. Just remove those capacitors and you should be good to go.


THHHHAAAAANNNKS worked now 

Since this is a ramped coil, you are trying to utilize the AC input (sine wave) ramp shape. With the filtering capacitors you are effective getting rid of that and smoothing it all out. So the coil is getting a high voltage pulse at startup.

The only other thing that you might need to verify is that the zero cross AC transformer is in phase with the AC bridge input. If you dont get any arcs after removing the filtering caps, try reversing the zero crossing transformer input.

nice build btw, those are some hefty resonant capacitors!
which build? it's just the test crappy test look.
Later it looks like this QCW where I currently wait for the "Simple Driver" from Ukrain but you know the war and the struggle there is real, I mailed already with he is still alive but he spend nearly every day in a bunker somewhere in Kiev and don't get parts :-(

[ZakW]

You're welcome! Happy to hear that it is working now.

-Zak

[Admiral Aaron Ravensdale]

Nice!
This is how QCW Sparks should look like \o/
https://photos.app.goo.gl/DHpoqBSRY8W7kuWW8

@ZakW Got all my HV Caps from aliexpress Dawncap is a really good brand.
https://de.aliexpress.com/item/4000314891877.html
https://de.aliexpress.com/item/1005004990716404.html
But take care that you order DTR caps

[ZakW]

Nice output, thanks for sharing!

[alan sailer]

It looks like that antenna is getting a workout. I see corona coming off the tip during every pulse.

The "simple driver" works great. Used it two coils, a DRSSTC and a QCW.  Glad to hear Eugene is still OK. He is a good guy...

Cheers.

[Admiral Aaron Ravensdale]

Ok here is a Video with my new 20A Varicac I get the full power out.
I already get 2 of them up and running, but can´t use them both at the same time because of the antenna!
Now I want to switch it to a feedback transformery the solder pads on the board mention already, but nowhere is mention the ratio for this!
Should be the standart 1000:1 Ok?

https://www.youtube.com/shorts/0AJ4dut6pEU

[ZakW]

Nice output and build!

Should be the standard 1000:1 Ok?

That ratio is typically used for DRSSTC primary feedback. The ratio is so high because the currents are so large. Secondary currents are much lower, I typically see SSTC secondary feedback CTs with 50-100 turns. I have used around 80 without issues. If the coil doesn't oscillate with the CT try to reverse the phasing.

[Admiral Aaron Ravensdale]

Secondary currents are much lower, I typically see SSTC secondary feedback CTs with 50-100 turns. I have used around 80 without issues. If the coil doesn't oscillate with the CT try to reverse the phasing.

Ok this means also the "measurement is different? The single coil measure the base secondary wire to Ground like in your picture?
https://highvoltageforum.net/index.php?action=dlattach;topic=2338.0;attach=16458;image

[ZakW]

The output of the secondary CT feedback is similar to the antenna feedback. Probably a stronger signal and definitely more reliable. You shouldn't need to make any modifications to the feedback input. One wire to where the antenna goes and the other side to ground.