I think the problem is coupling. When coupling is high the inductance of the primary is affected by the secondary. When coupling is low this effect is small enough to tune for but my coil is at least 0,50. The measured inductance of the primary decreased significantly when the secondary was placed. The primary needs to be larger to reduce the coupling. Back to the drawing board. Some pics:

(too) high k primary



Driver (don't know what version it is) + GDT + inverter, powered bij 30VDC PSU.



Driver schematics (interupter and sound circuit excluded)



Scope traces: sine wave is secondary coil voltage, square wave is TC4422 output probed at TP3. I expect (correct me if i am wrong) to see the driver to switch when secondary voltage peaks (+ or -) when tuned correctly.

Hello all,

After building a few slayer exciters it was time to try a DRSSTC. I quickly realised that the parts would cost way more when bought separately than the assembled PCB's, so I bought the driver, GDT and inverter of the shelf and build the rest myself.

I build the secondary and checked the Fres with my oscilloscope. Next, I built the primary and roughly tuned it to the same frequency. The PCB's do what they should do and the primary coil runs smoothly on it's own. So far so good.

When I put the primary and secondary together, the frequency jumps by 30%. Coupling the coils somehow causes the CT current phase to start leading by 60° and pushing the frequency up resulting in no ZCS, and low efficiency. Tuning has no effect at all.

What is the cause of the leading phase and what can I do about it?