High Voltage Forum

Tesla coils => Solid State Tesla Coils (SSTC) => Topic started by: Maverikie on April 16, 2021, 09:22:47 PM

Title: Help needed with SSTC. First TC build
Post by: Maverikie on April 16, 2021, 09:22:47 PM
Dear HV member,

I'm new in the TC coil business. I'm trying to build a SSTC with inspiration from SSTC 5 from Steve Ward and SSTC 2 from Loneoceans. Ofcourse I have deviated from the suggested schematics.  ;D

So i've build the interrupter based on a ATTiny and the driver is based on two UCC37322P chips. One inverted by a SN74HC14N. It seems that the interrupter and driver are working fine. I think I've problems with the half bridge consisting of two IRGP50B60PD1.

So when I try to turn everything on, it's drawing a lot of current via the Variac. See below the schematic.

(https://highvoltageforum.net/proxy.php?request=http%3A%2F%2Fwww.bramsclassiccars.com%2Fwp-content%2Fuploads%2F2021%2F04%2FSchermafbeelding-2021-04-16-om-21.04.20.png&hash=baed07f557e6f597171a5c1d62118f35dfe4b3ff)

I used my scope to measure the following:

First pic.1: Gate of Q1
2: Gate of Q2
3: Input signal generator sine wave 150 khz
Second pic.1: Output UCC37322P without GDT
2: Output UCC37322P without GDT inverted
3: Input signal generator sine wave 150 khz.

(https://highvoltageforum.net/proxy.php?request=http%3A%2F%2Fwww.bramsclassiccars.com%2Fwp-content%2Fuploads%2F2021%2F04%2FDS1Z_QuickPrint1.png&hash=a4823a5f48db29f8ad69f92c48b5d0322fb7f4f0)
(https://highvoltageforum.net/proxy.php?request=http%3A%2F%2Fwww.bramsclassiccars.com%2Fwp-content%2Fuploads%2F2021%2F04%2FDS1Z_QuickPrint2.png&hash=b3fc3e8f73a33d0c862f6d29740929a738286ecf)

Below pictures of the general setup:
(https://highvoltageforum.net/proxy.php?request=http%3A%2F%2Fwww.bramsclassiccars.com%2Fwp-content%2Fuploads%2F2021%2F04%2FIMG_0897.jpg&hash=0fa9665a2dcdc313c757601632d05cde4c85e904)
(https://highvoltageforum.net/proxy.php?request=http%3A%2F%2Fwww.bramsclassiccars.com%2Fwp-content%2Fuploads%2F2021%2F04%2FIMG_0898.jpg&hash=52d75cc8bf8449f1ad91b350a8358a72e6b7e0cf)
(https://highvoltageforum.net/proxy.php?request=http%3A%2F%2Fwww.bramsclassiccars.com%2Fwp-content%2Fuploads%2F2021%2F04%2FIMG_0900.jpg&hash=060f7a848b77d3c5092d19ec10d5784eeed54bb8)
(https://highvoltageforum.net/proxy.php?request=http%3A%2F%2Fwww.bramsclassiccars.com%2Fwp-content%2Fuploads%2F2021%2F04%2FIMG_0901.jpg&hash=f77c70ca4c4d7de5d9d8dff54bdadb37d5aa3720)
(https://highvoltageforum.net/proxy.php?request=http%3A%2F%2Fwww.bramsclassiccars.com%2Fwp-content%2Fuploads%2F2021%2F04%2FIMG_0902.jpg&hash=35be006ef28d541e0f2d0acf7077c443ea69aa33)
(https://highvoltageforum.net/proxy.php?request=http%3A%2F%2Fwww.bramsclassiccars.com%2Fwp-content%2Fuploads%2F2021%2F04%2FIMG_0903.jpg&hash=b6ec041d58d09eaf60d35bf297608d2abf011949)
(https://highvoltageforum.net/proxy.php?request=http%3A%2F%2Fwww.bramsclassiccars.com%2Fwp-content%2Fuploads%2F2021%2F04%2FIMG_0904.jpg&hash=f72b6adf8e772e9fc59c619cee9f4af2cb65a32e)
(https://highvoltageforum.net/proxy.php?request=http%3A%2F%2Fwww.bramsclassiccars.com%2Fwp-content%2Fuploads%2F2021%2F04%2FIMG_0905.jpg&hash=6d6d15ee48bc7caaf65124eb6ad7f316ab13b414)
(https://highvoltageforum.net/proxy.php?request=http%3A%2F%2Fwww.bramsclassiccars.com%2Fwp-content%2Fuploads%2F2021%2F04%2FIMG_0906.jpg&hash=37874504e7d67ae468084f23184ed3858cac4c2f)


Title: Re: Help needed with SSTC. First TC build
Post by: davekni on April 17, 2021, 05:36:49 AM
First issue appears to be wrong core type for GDT (and likely CT too).  Cores must be high-permeability ferrite, not powdered iron.  Mads has a good GDT tutorial, with links to it in several of his posts.  (Other GDT and CT construction info is around too - do some searching.)  Besides core type, it is best to have a 1:1:1 turns ratio wound with twisted-pair wire for low parasitic inductance (with gate-driver chip input power at 15V for IGBT drive).  1:2:2 can be constructed with reasonably-low parasitic inductance, but that is a bit more tricky and increases gate-driver load.

Second likely issue:  I don't see any insulating pad under IGBTs.  They need either insulation or separate insulated heat sinks.  The bottom surface is electrically connected to collector.

Plug-board construction is often problematic, especially for gate-driver chips with their high switching current peaks.  However, your construction is the cleanest I've seen for plug-boards, so you may be fine with that.

If you haven't tried JavaTC, that is a good idea to check your coil parameters for reasonability.

Great documentation with detailed pictures and scope traces!  That makes assistance so much easier than for many initial requests.
Title: Re: Help needed with SSTC. First TC build
Post by: Mads Barnkob on April 17, 2021, 09:34:02 AM
Hi Maverikie and welcome to HVF :)

Davekni is fast and catches it all before any other can even finish sleep to reply ;)

Your IGBTs are not insulated, on page 10 you can see that the cooling connection on the back of it is assigned to Drain: https://www.infineon.com/dgdl/Infineon-IRGP50B60PD1-DataSheet-v01_00-EN.pdf?fileId=5546d462533600a401535656c5e9248a you you are effectively shorting out your two drain channels.

The GDT troubleshooting guide is written by Richie Burnett: http://www.richieburnett.co.uk/temp/gdt/gdt2.html
Title: Re: Help needed with SSTC. First TC build
Post by: Maverikie on April 17, 2021, 07:20:58 PM
Thanks a lot! Stupid mistake :-[.

I found out that I fried my IGTB's, but I had foreseen some rookie moves, so I already bought two extra ones.

When I replaced the originals I tested and got my first spark!! 8) 8)

I checked the waveform of my GDT and it seems good. See scope pic.

But right now I have problems with my heating boiler. Seems it doesn't like the RF noise on the mains ground. In my situation it's quite hard to have a separate RF grounding rod installed. I'm reading something about a line filter can be used to suppress the voltage spikes to mains ground. Anyone experience about this?

(https://highvoltageforum.net/proxy.php?request=http%3A%2F%2Fwww.bramsclassiccars.com%2Fwp-content%2Fuploads%2F2021%2F04%2FIMG_EDCCFEBCA52A-1.jpeg&hash=ee961fb27d47db05d63d12bb23e8d9e313873535)

(https://highvoltageforum.net/proxy.php?request=http%3A%2F%2Fwww.bramsclassiccars.com%2Fwp-content%2Fuploads%2F2021%2F04%2FDS1Z_QuickPrint3.png&hash=9db38662215eba655ac82ae3a3b6e87f181d1368)
Title: Re: Help needed with SSTC. First TC build
Post by: davekni on April 18, 2021, 01:24:59 AM
Quote
Davekni is fast and catches it all before any other can even finish sleep to reply
Yes, I live in Oregon (west coast of USA), so in one of the later time-zones of forum users.  My evening-time covers almost anything posted throughout the day.  You have many more tutorials and examples of coil builds - more helpful in many cases than my myopic focus on specific issues and questions.

Quote
I checked the waveform of my GDT and it seems good. See scope pic.
Yes, I agree.  Fried IGBTs is a reasonable explanation for your previous gate waveforms rather than inappropriate GDT core choice.

Congratulations on first sparks!
Title: Re: Help needed with SSTC. First TC build
Post by: Maverikie on April 28, 2021, 10:14:06 PM
It's working finally! Full power.

The interrupter circuit based on Attiny performed not so well. At higher power the input pins of the drivers went self-oscillating. And the Attiny turned itself of. I tried to shield it but didn't succeed. Any suggestions?

I tried the NE555 circuit from Steve Ward and it worked wonderful!

(https://highvoltageforum.net/proxy.php?request=http%3A%2F%2Fwww.bramsclassiccars.com%2Fwp-content%2Fuploads%2F2021%2F04%2FIMG_0972-scaled.jpg&hash=07d0d02c6b850a5cc10451793dd83685a0e03a1d)
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