Electronics > Projects, Designs, and Technical Stuff
DRSSTC TESLA COIL problem and MONEY reward for working solution
justin66:
hello guys. fist i want to say i will pay 20 euros for a person who can help me sort this problem out i can give more if you offer extended help
short about this project it is my graduation project that i cant get to work. I have to finish it as quick as possible that is why im offering money. I hope its enough because i have spent too much on this coil already. its almost 350euros for all the components that keep blowing or not working. im tired of wasting money on it and i need smarter people advise.
short about me and my equipment i have multimeter, clamp meter for measuring current ac/dc, osciloscope dso138 witch is good for 100khz at most. i can access a good one in my college.
i have decided to make drsstc TC for my finals that i kind of regret it, because it didnt turn out the way i wanted. im stuck with it and i need to finish it ASAP. i have electronics as a hobby and my speciality is electrican
short about my TC i decided to use already polished designs that are available on the internet. but it still doesnt work for some odd reason. i use DRSSTC design witch contain Universal driver UD2.7c full Hbridge bridge and an interupter. it seems easy at first, just order some pcbs, put it together and wuala. but i got stuck now. i think i have assembled my devices correctly. i got it working several times, but the result is not what i hoped.
UD2.7 http://www.loneoceans.com/labs/ud27/
H bridge design https://github.com/profdc9/DRSSTC-PCB-Pack/tree/master/full-bridge-transistor
interupter https://easyeda.com/stuarth/steve-ward-s-drsstc-interrupter-with-burst-mode
my trial and error srory i goofed a lot of trial and error tries to get it working. i blew my transistors at least 4 times now.
on first try i can verify, my boards should be working to some extent interupter is definetly working. UD2.7 should be working because my gate drive transformer makes noise according to interupter pulses.
my h bridge should be working, verified with osciloscope, although the drive is not looking the best, at least on the first power up when i had a good osciloscope to probe around. on feedback i ran signal generator to check if it is working.
first i blew a single audyn brand polypropilene capacitor rated 550VAC 0.1uf i saw sparks of 1mm when metal object is near secondary.
then by grounding my primary coil i blew IGBT transistors
then i bought new audyn polypropilene caps, this time 4 in series making it 2kv ac capacitor close to 0.1uf i saw 1mm of sparks as well
then i blew transistors again, probably because my Gate drive transformer was 1:2 ratio making it 48v on IGBT gates
then i bought expensive snubber capacitors, they are called CDE capacitors 0.068uf, steve ward used them. it is 12 pcs bank, 3 series, 4 paralel, making it 0.09uf bank of caps
i changed up my primary design a bit, because it seemed that the most voltage is at the middle of the secondary. so i changed cylinder shape primary to pankake. my coil worked like a charm, except it was making sparks 3mm to air and maybe 3cm to grounded object. not the best result. the worst part i had to turn up my interupter and my variac. my variac was at maximum 250vac and my interupter was turned to pretty high pulse frequency and probably maximum pulse with. suddenly my apartments lights went black. i blew IGBTs again. |O
Now i found two older pair of transistors that seems to be ok, at least with multimeter diode test mode, so i was lucky and im left with two blown and two kind of ok transistors, so i slapped old pair and new pair of transistors, seems ok everything is working again, this time my GDT seems to change pitch quite differently. i kind of got it working with variac at 180vac, before last blow up by the GDT sound the circuit was geting into a working state as low as 90vac on variac, now it need at least 160vac to go to working state. this state is when the gdt is silent it means circuit is working. and then gdt is noisy it means the circuit is not working correctly.
so this circuit seems to go to working state. the GDT is silent, so my current transformers should be seeing current and giving it to the feedback. i can hear EMF disruptions through my PC speakers. but the funny thing is, no sparks what so ever. i tried different MMC(capacitror bank) and the old one with no sparks this time
additional information my GDT and current transformers are ferrite toroids from car audio amplifier boost converter circuits. 500:1
the MMC capacitors is CDE cap bank with 6kvdc rating, i also have ceramic type mmc with 5kvdc rating, the little equipment i have says that they are good. transistor tester mk-168 and multimeter shows correct capacitance.
my tesla coil primary is about 3 turns, the secondary is about 1050 turns with former with unknown plastic. it has 0.4mm copper wire and former radius is 4.3cm and diameter is 8.6cm. winding height is about 43.5cm
i also have top load toroid that doesnt seem to affect things
there is optional resistor values on the Hbridge circuit that im not sure witch one to use and im using IGBTs that are suggested in base of materials list for the Hbridge circuit
couple of pictures of my project:
https://ibb.co/album/c7yhfa
dmills:
I am seeing a hell of a lot of lead inductance there and copious potential for noise pickup in important things like transistor drive connections, also some very small leads in what I would expect to be high current places.
Can we have a circuit diagram of exactly how you have that lot hooked up (including such things as exactly what is connected to what ground wise).
Have you set the phase lead and over current thresholds as described in the UD2.7 documentation to suit your primary and cap bank (These will need readjusting any time you change either)? You should not be blowing IGBTs.
Does the secondary resonate at the same frequency as the primary? Not going to get much spark action if not, but the electronics setup can be done without the secondary even installed (Tesla coils are LOOSELY coupled systems)!
justin66:
hi, thanks for the reply,
i used internet cat5 cable for this task as a steve ward did for the GDT. this is just a temporary setup to get it working with at least 5cm sparks its meant to be easy to change things up. and after some reasonable results assemble a proper stand for the TC and put all LV electronics inside aluminum and sheet boxes for higher power use. at least this was the plan, correct me if im wrong. im planing on building wood stand today.
should i remove all the connectors and solder in the wires directly? im not sure if it will help that, but i will do this if you say so.
the leads are 1.5mm2 just a temporary/testing solution as well. what thickness wires i should use?
connection diagram is this https://ibb.co/zhnWbXQ BTW ground is my apartment central heating radiators that is for sure ground. we dont have ground coming out of outlets.
i used to use phase inductor as fixed value 10micro henries. recently i recieved DIY adjustable inductor and i made it roughly 10microhenries. it did change the sound of the GDT when adjusting. so i set it to the most audible sound setting. i didnt have a chance to use osciloscope yet, i can probably arrange it tomorrow.
as of adjusting the OCD i didnt think it is necessary as im not going to run it to high sparks, i also keep track of the variac current and it doesnt rise what so ever using my digital clamp-multimeter
i didint think measuring resonances mattered much because i calculated this in java tc. im going to do this probably tomorrow as i get a chance to use the expensive equipment.
the strange part is before the last blow it kind of worked with the sparks. now im not sure if CDE caps are blown they measure mostly full capacitance with in my eqipment mesuring tolerances. some read a little bit less. when i change phase jumpers the TC refuse to work by the sound of GDT.
i tried using steel pancake for primary testing, the results are the same, no current, my pc speakers react to the operation by making interupter sounds assuming that the UD adjusts the drive frequency to the primary it is very strange that nothing happens, other people indicated that the pan should heat up. not in my case. and im sure it is compatible with induction heaters.
i know im doing something wrong but i cant pin point what it is. maybe some ideas?
daedalux:
Have you tried to drive an artificial load made out of resistors with simulated feedback? If that works okay shield as well as you can. You can serve yourself with aluminium tape and perhaps coaxial cable in some places. Any IGBT or MOSFET is very likely to get killed with high voltage and frequency just around.
justin66:
thanks for the reply, i dint tried this, how do i make this? do i just connect some resistance across Hbridge output? what resistor value i should use for this application? and what variac voltage?
BTW im using 4pcs of FGY75N60 IGBT
the Hbridge driver has some TVS diodes, i thought they are supposed to take care of the overvoltage spikes? the schematic is in the first post at the Hbridge link
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