Testing the driver board

[donnersm]

Hi all,
Just wondering...would it work to test a drsstc driver board while using a lightbulb instead of the primary coil. That way i can use my scoop to measure all the signals on the board without the high voltage....

I'd expect to see and trace the sinewave from the feedback transformer until the driver ...It would be different and the resonance frequency will be completely off.
but what do you think ...would it work?

purhaps anyone wrote a good piece of info on how to tune , adjust etc the driver board. I will be using UD2.7c

[Hydron]

You need the LC circuit to oscillate and provide feedback to the driver.
I would suggest powering it up with a bench PSU to begin with - a few 10s of volts should normally be enough to get some oscillation and it's hard to blow up IGBTs at these power levels. Still keep clear of the connection between the primary coil and capacitor - it could still be at a relatively high voltage, though unlikely to be that scary.

[donnersm]

Thanks hydron,
So I guess I’ll stick to my variac trafo for the bus voltage and then simply leave out the secondairy coil for testing.

[Hydron]

I'd still recommend a bench supply to begin with - can limit both current and voltage and is isolated and safe.

[Mads Barnkob]

Put some metal inside your primary, a pan or bowl with water in it, so absorb the energy from your primary circuit, so current wont ring up that fast either and it is a good dummy load, also a simple metal sheet can be put on top of it, it is after all just a induction stove

I normally test my driver with signal generator first and then you only have to deal with phasing of feedback CT once it is mounted on the coil.

I also use a variac to power up the bridge, with analogue meters so its easy to watch the current and see if something is shorted or its peaking with small bumps as I use a interrupter set at 1-2 BPS.

Tuning the primary should really just be done from a JavaTC simulation and maybe detune your primary 5-10% lower than your secondary to start with, this should be a perfect start, then play around a bit with fine tuning the tap, only moving it a few centimetres at a time until you get a satisfying spark length.

[donnersm]

@Mads Barnkob Thanks I did just that...I removed the secondary coil and replaced my 230V bus voltage by a bench power supply of 30 volts...this was enough to test the resonance frequency and measure some signals on my board...for now still the onetestla TS board..without blowing it up!  lol......it was a good idea to do this..it makes my understand how it all works even beter... And surprisingly Although the bus voltage was only 30V dc.... i measured voltage of 200 volts over the primary coil( 5turns with 125mm diameters...

@Hydron thanks for the idea of using a bench psu
Can't wait to see it make some sparks using a variac trafo. AFter that on to my UD2.7!