My first half bridge SSTC

[Acid Byte]

Hey guys and girls!

After seeying many great builders on the internet succesfully building awesome SSTC's,
half year back i wanted to build my own.
Though circuitry isn't super complex at first glance.
By the time you get something to run you find out it's rather complex but in a different way.
As i believe we all expirienced it isnt that easy at all when starting on this at first!
With that said i can now show my first build.

My build is a combination of what i've seen out there and from my own expiriences.

Frequency of the secundairy is about 144khz
Its a half bridge design using 2 cap (resonant cap) in series on one side of the half bridge (coil at center tab and 1 cap going to vdc+ and one going to vdc ground)
This does provide a better coupling between coils (in terms of frequency) but doesnt give that sweet resonant rise ( atleast not like with drsstc's).
The logic board i used is the one designed by Matt Giordano wich is a pretty simple board but works fine anyways!
Im using a antenne for the feedback (i had some issues with the current transformer distorting the signal to the schmitt inverters wich gave some strange sounds to the sparks and didnt allow the voltage on the secundairy to go sky high...)

Overview components (some things have changed since)


Logic Driver Board by Matt Giordano


Overview Components


Overview Components


Half Bridge Schematic


Logic Driver Schematic


The old setup.

This setup really gave lot's of headache because the secundairy was just way to long for the current running in my primary.
Lots of arcs from primary to secundairy when it got up to higher arcs.

Current Setup



To build this it took me about 5 months of time destroying many many mosfets!!

Old Setup

/>
Latest Setup (sorry for the shity video... my camera added a filter because of the EMI)

/>When i have some time ill shoot a better one

If you have any questions about the build feel free to ask!!
And also if you have thoughts of how it could do better yes please!!

Greetings Jeroen

[futurist]

Thanks for the writeup, nice coil!

Though circuitry isn't super complex at first glance.
By the time you get something to run you find out it's rather complex but in a different way.
As i believe we all expirienced it isnt that easy at all when starting on this at first!

I agree with you, exactly how I felt when I started to build my first coil.. some things you thought were simple just start to go wrong

[Acid Byte]

Thanks for the writeup, nice coil!

Thank you!
Its a good start into the more serious coils

I agree with you, exactly how I felt when I started to build my first coil.. some things you thought were simple just start to go wrong

Yeah and everything sterts to go wrong haha!!

[Mads Barnkob]

That is great for a first SSTC and hopefully you will find it a good step towards building more complex coils like a DRSSTC.

First impression improvements for longer sparks are:
- Tighter coupling between primary and secondary coil, wind that primary coil directly on the PVC pipe as a helical coil (A bunched together coil of wire like you made have a much higher loss due to self induction, the outer turns simply use some of their energy on heating up the inner turns)
- Reduce primary turns, but be sure to calculate the currents, to avoid blowing up many more MOSFETs
- The wire length from DC bus caps to the MOSFETs are way too long, these should be as short as possible! The same goes for the wires in the primary circuit, to the primary coil. Did you you my chapter on primary circuit design? http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/busbar-and-primary-circuit/
- Higher DC bus voltage, do you have 3x400VAC? Or use a voltage doubler, if you can stay within the voltage rating of the MOSFETs

[Acid Byte]

That is great for a first SSTC and hopefully you will find it a good step towards building more complex coils like a DRSSTC.

Thanks yeah i'm planning on a DRSSTC right now
Have to figure out some stuff...

First impression improvements for longer sparks are:
- Tighter coupling between primary and secondary coil, wind that primary coil directly on the PVC pipe as a helical coil (A bunched together coil of wire like you made have a much higher loss due to self induction, the outer turns simply use some of their energy on heating up the inner turns)

Indeed its nothing close to ideal.
In the beginning i had a much closer coupled coil but had lot's of difficulties with arcing from primary to secundairy (or the other way arround)
This was probably due to not enough current in the primary.

- Reduce primary turns, but be sure to calculate the currents, to avoid blowing up many more MOSFETs

Im still not sure how to calculate the currents running in the primary.
Can you point me out wich formula's to use? (EDIT: i allready found the awnser on the forum)

- The wire length from DC bus caps to the MOSFETs are way too long, these should be as short as possible! The same goes for the wires in the primary circuit, to the primary coil. Did you you my chapter on primary circuit design? http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/busbar-and-primary-circuit/

Havn't read it yet but i will! thanks!
Yeah all wires are to long gonna fix that in the next coil! (or maybe in the future)

- Higher DC bus voltage, do you have 3x400VAC? Or use a voltage doubler, if you can stay within the voltage rating of the MOSFETs

For the homes we only have 1x 230VAC.
So a step would be using the voltage doubler with better mosfet or IGBT. (now running on irfp460)

Greetings Jeroen

[Mads Barnkob]

If you have questions, then start a thread in the DRSSTC section and you will get some help if you have specific questions

I saw on facebook that you tried a new primary coil with better results, but properly also higher primary currents, there is a thread just under yours here in forum where primary current in SSTC is discussed: https://highvoltageforum.net/index.php?topic=40.0

The reason I advocate helical or pancake coils are that they have a geometry that makes them able to be calculated, which can be real hard for a "bunch" of wires

If you have any questions to the DRSSTC design guide, things you do not understand or think could be explained better, you can add them in this thread: https://highvoltageforum.net/index.php?topic=38.0

[Acid Byte]

I saw on facebook that you tried a new primary coil with better results, but properly also higher primary currents, there is a thread just under yours here in forum where primary current in SSTC is discussed: https://highvoltageforum.net/index.php?topic=40.0

Yeah again had some arc overs so rewound the primary + took a turn off.
wound it a little bit like a rodin coil (torus knot shape) just to see what happens

The reason I advocate helical or pancake coils are that they have a geometry that makes them able to be calculated, which can be real hard for a "bunch" of wires
If you have any questions to the DRSSTC design guide, things you do not understand or think could be explained better, you can add them in this thread: https://highvoltageforum.net/index.php?topic=38.0

Could it be that the torus knot shaped primary would be more efficient in transferring the power? (it sure looks like it way better then the bunch of wires together!)
I know it's not a ideal situation but for now it's ok.

when i have read your guide i can start being more serious in the build (at the moment because i dont have all the knowledge most of the time is just trail and error for me. (wich does seem to give me alot of expirience ))

anyway ill be building alot more coils to see what happens in different situations.

[Acid Byte]

A few updates on my half bridge coil.

I redid the primary and made a helical for it with much better coupling to the secundairy.

Also redid the inverter stage.

So this is the new 10 turn 6mm2 primary coil


And here is the new inverter layout on hand drawn pcb.
Now using 2x fgh60n60's in parallel a side