Universal Driver 1.3b doesn't oscillate

[PATWORK007]

Hi, it's my first time posting here, also it's my first time building a DRSSTC with an appropriate driver.

I used Steve Ward's UD1.3b modified with 2 TC4422 for driving the GDT and coaxial cable for Interrupter.

Here is some info about my DRSSTC:

-Server EMI Filter 20EEJ1 at power stage input.
-AC Voltage Doubler Rectifier with 2 1000uF Capacitor in series.
-Half-Bridge configuration with 2 FGH60T65SQD-F155 650V 60A TO-247 IGBT's.
-2 CT for Feedback and OCD 1:32:32 each.
-For Primary LC tank I used Cornell Dubilier Capacitor 940C30P1K-F 3KV 0.1uF.
-Top load made of Air duct pipe

At first I used a primary coil of 5 turns of copper pipe, I used my osciloscope probe shorted for making 1 turn near primary coil and the driver worked, even the OCD led lit up when I cranked up the voltage with my variac, but the problem was the resonant frequency of the primary was too high (~260 Khz) for my secondary coil (~130 Khz), so I made a new primary coil with 16 Turns of 12 AWG standard electrical cable on a 6" PVC tube connector (I made the calculations using JavaTC).

So I connected everything again and cranked up the voltage with my variac and it didn't oscillate, even I reached around 340VDC on the DC bus but nothing appeared on the oscilloscope nor  the OCD led.

And there's another question I have about UD1.3b: What is the Ideal voltage I can set the OCD comparator pin with the 10k pot to protect my IGBT's?

[davekni]

So I connected everything again and cranked up the voltage with my variac and it didn't oscillate, even I reached around 340VDC on the DC bus but nothing appeared on the oscilloscope nor  the OCD led.

I'd guess that phase needs reversing (feedback CT leads swapped).  At high frequency sometimes drivers have enough delay to oscillate with reversed phase, but not at lower frequency.  Less likely possibility is missing bleed resistor from line doubler center to half-bridge output to insure starting condition is with half-bridge output center-supply.

[PATWORK007]

So I connected everything again and cranked up the voltage with my variac and it didn't oscillate, even I reached around 340VDC on the DC bus but nothing appeared on the oscilloscope nor  the OCD led.

I'd guess that phase needs reversing (feedback CT leads swapped).  At high frequency sometimes drivers have enough delay to oscillate with reversed phase, but not at lower frequency.  Less likely possibility is missing bleed resistor from line doubler center to half-bridge output to insure starting condition is with half-bridge output center-supply.

Yeah I tried to flip FB CT leads but didn't work, and yeah my capacitors have 100k bleed resistors each

here are some photos of my setup, first with the coil that makes the Driver work (copper pipe one) and then the 16 turn 12 AWG

[davekni]

here are some photos of my setup

Photos always help.

Next step is to scope signals at start of enable pulse.   Scope both GDT inputs (UD1.3 outputs).  Scope CT input.  That will likely be enough to show issue.

Wrong GDT core material would be another possible cause for your symptoms.