Hi there!

This post is the first in my life where I share my experiences with others regarding high voltage

I have quite a lot of experience with classic coils, I made one SSTC educationally, but this is my very first DRSSTC. I thought it was worth sharing my impressions as my project contains some "brave" things.
If you feel like saying "you're doing it wrong, stupid Noob!". Feel free! Every remark is valuable!   





"OK CHUMS, LETS DO THIS"


My assumptions:

• Single phase power supply - 230V, 16A (later I want to make additional and optional 3 phase power supply)
• As small as possible for the given power
• Everything done with as much margin as possible, especially the inverter
• SKP feature is a must!

During construction I fell ill with a disease known as "a good upgrade is not bad" and "it's never perfect enough" before I tested my previous solutions I changed them... So my TC have evolved as the project evolved and for now my technical data looks like this (I hope it's mostly the final one  ):

• Full bridge of: 2x 2MBI400U4H-120-50, 1200V / 400A
• DC BUS caps: 4x 6800uF / 450V 2s2p for 6800uF / 900V - there's no to much bus capacitance, right Guys? (I upgraded DC BUS caps 3 times for this bridge only...)
• Snubbers: 2x 3.3uF + 2x 2uF for 2x 5.3uF
• Power: single phase 230V / 16A with voltage doubler
• Secondary: 16x42cm, wire: 0.2mm
• Toroid: alu. tube 12x46cm
• Primary: flat, copper tube 4.7mm, 15 - 30uH (depend of MMC capacity and efects)
• MMC: (so far for testing) old Russians paperoil caps K41-1a 100nF / 10kV 1s2p for 200nF / 10kV or 1s3p for 300nF / 10kV
• Rez. freq: 65 - 70kHz
• Primary current: 600 - 800A (depending on the obtained results)
• Driver: SKP DRSSTC driver from aliexpress like this: https://highvoltageforum.net/index.php?topic=561.0 with many upgrades... Yeah, yeah I didn't know about profdc9 driver  Besides, I was curious how this driver works and I had it at hand.

Everything looks quite typical so far, but let's focus on the bridge and frequency for a moment.
Lets take a look on the datasheet of 2MBI400U4H-120-50:


If you add up the third column with the max switching times you get about 3.1 centuries. That's a lot... Especially when you need to drive these mammoths to 70kHz.
To sum up, I had an IGBTs not tested in DRSSTC by anyone, with switching times bigger than an acceleration of container ship, working at a fairly high freq.
I didn't see any reason why this shouldn't work.

But! Before you doubt people and all that is alive, take a look at the oscillograms:

(yelow: G-E voltage, purple: bridge output, blue: primary current)



IMO it's not bad. A lot of phase lead is needed but there is not even a shadow of voltage spikes in the output. It's suprise me a lot!
So I actually have a fairly powerful inverter that I drive very fast but I'm planing to get 600 maybe 800A max in SKP mode. I don't think any more current would be needed. Already at this value, I will probably exceed the permissible power of one phase and I will make my neighbors despair.

One more funny thing about the bridge, it's not the initial version ...of course, and this element was upgraded during the development of the project

...exactly three times

My bridge is like Pokemon, evolves:


Legend:

• 4x 30n60 TO-247 IGBT mounted on PCB from aliexpress, I used it for testing this exotic driver at the very begining - it's always better to blow up TO-247 than bricks - the shards are lighter
• 4x IXGN60n60C2D1 ISOTOP minibricks from aliexpress - this was supposed to be my final bridge
• "The Big Mama Bridge" because bigger is better

Pre-assembly:


I drive both IGBTs with two GDTs made by 3E25 42 / 25mm. I highly recommend cores made of this material, waveforms are perfect, no dropouts, perfect squere wave even at low frequencies!
Of course, they don't look like this on the screenshots because IGBTs works under load and the waveforms are distorted by the parallel inverter output and CT measurements.

Now MMC:


Those capacitors are robust, but they have high dielectric losses and high ESR, which makes them extremely hot! The effects also leave something to be desired, I compared them with the MKP10 in my classic tesla and they give about 10-15% worse results.

And now something for masochists and how to NOT to make the primary coil:


It took me 6 hours to thread the pipe through these holes!

And the most intresing think, THE DRIVER:


I could write a book about this driver, but maybe not in Chinese. This alone is an interesting thing that this miracle drives my two fat 2MBI400s without any problems. This is a very good and a very bad think at the same time. It has many pros and cons. So I made a lot of improvements there, some were necessary.

Let me know if you want to know anything about this toy, maybe I will write a separate topic in the form of a small documentation?

-------------------------

Now you say "where are the lightnings?" So far I've tested my Tesla with 2nd version of the bridge, and managed to easily reach 110cm at 400 amps, 200-350us and 200bps. It works great! But still I have feeling this is a lot for mini-blocks from aliexpress and their time would be counted in this configuration. That's why "The Big Mama Bridge" was created and it is waiting for the first tests as a Tesla Coil instead of an induction cooker 

In the next posts I will send some photos, maybe a short video from the first tests on IXGN60n60C2D1.