High power clean audio SSTC

[AstRii]

Hello! Recently I got my hands on driving SSTCs with Phase Lock Loop drivers and let me tell you, it's an amazing way of driving the coil. Not only it's the safest solution for the transistors, it also allows for clean audio modulation.
I have made a small (~1kVA) PLL driven coil for my university and now I wanna make one for myself and make it big My goal is to draw as much power as an European 16A outlet can provide (>3.6kVA) and I thought I could share the project here.
So this is my SSTC II:




CW mode (>2.5kVA)

Some basic info:
Fres: ~315kHz (without arc)
Secondary: 12.5cm wide 47cm tall wound with 0.5mm wire (820 turns), 32K reactance at f0
Primary: 16cm wide, wound 8 turns with 5mm wire
Bridge: Double full bridge of IRFP460 FETs
DC-blocking capacitor: 2S2P combination of 1uF 630V WIMA capacitors for total of 1uF 1260V
Power in 50Hz mode: ~1.5kVA (200VAC input voltage)
Power in CW mode: ~2.5kVA (200VAC input voltage)
Coupling: ~0.315
Topload: 6cm x 25cm bought from eBay
DC bus capacitors: 7800uF 400V
Heatsink: 260mm x 130mm x 60mm aluminum heatsink with two 5W fans blowing air on it

I'm using my own driver (heavily inspired by https://www.vn-experimenty.eu/teslov-transformator/sstc/sstc-5.html) with 4046 phase lock loop chip, which is set to oscillate at ~311kHz. The beauty about this design is that it uses Bluetooth module to which I connect with my phone and playback clean mp3 audio.
I've put much more info about the coil on my new website: https://www.uhvlab.org/sstc-ii (not optimized for mobile phones yet )

Right now the coil is running cool, transistors reach maybe 10C above ambient after 10 minutes of CW operation. ~20C above for the secondary coil, but the main problem here is the primary. Primary coil gets quite hot even after 10 minutes of CW operation at 200VAC input voltage (roughly 2.5kVA). I need to use litz-wire for the primary and then I will try to increase the coupling and run it at full projected power.
I want this coil to be able to run continuously for hours in CW mode at full power.

[Duane B]

Very nice! Thanks for sharing!

[AstRii]

Thank you so much! Glad you liked it

[davekni]

Nice coil.

My goal is to draw as much power as an European 16A outlet can provide (>3.6kVA)

3.6kVA (220V *16A) is a great goal for long-term operation.  3.6kW at 3.6kVA requires 100% power factor.  You can get close to 100% by running 100Hz (no bulk cap) or by adding a PFC supply between line and bulk cap.

Or, you can get 3.6kW by drawing more than 16A RMS and hoping the breaker doesn't trip and that there are no overheating connections in your building wiring.  Common strategy for shorter runs.

[AstRii]

Thank you Dave!

Or, you can get 3.6kW by drawing more than 16A RMS and hoping the breaker doesn't trip and that there are no overheating connections in your building wiring.  Common strategy for shorter runs.

This is kind of what I'm aiming for haha
I'm not planning to run the coil for hours continuously everytime, I only want the possibility. I often show my work on various MakerFaires and similar events, the coil should be able to run there throughout the entire event (dozen hours).
I think that FETs are not going to overheat anytime soon, secondary could be a problem even with 0.5mm wire and primary definitely needs litz-wire.