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Registered Member #76
Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458
okay, i already build all kind of teslacoils in all sizes, from small to big etc made everything with them, audiomodulating and so on, the only thing i never got to build was an oltc. i have 2 big toshiba igbt bricks rated at 1200volts and 200A continious 400A pulsed, should be big enough, but i dont know where to start. i know the bricks are used as a spark gap and are firing at 100 -1000bps or so with short bursts (on times of a few ys up to 100s of ys right?) the only thing i dont understand right now , why are there only 1 or 2 turn primaries and a big mmc with several yF? yeah bang energy should be large but wouldnt it work with say 5 primary turns and a mmc with several 100s nF?? this thing shouldnt get too big, just a small nice oltc and it has to be reliable (what a solid state coil is capable of, lol) another thing is, how can i tune it for good quenching? manual adjust the bps and on time until i get good results or measuring or calculating or so? the main idea was voltage doubler, charging choke for a calculated maximum peak of 800A (both bricks are connected in parallel)a primary with 4-5 turns, mmc cap with pulse caps(wima mkp or so) secondary with around 70khz-100khz and a whole lot of luck.the electronic is not too complicated just a normal interrupter out of a drsstc with small changes in maximum adjustment etc, gate driver ics ,gdt thats it, right? maybe a overcurrent protection what do you think? em and, how can i calculate the charging choke, resistive i think?
the only thing i dont understand right now , why are there only 1 or 2 turn primaries and a big mmc
The firing voltage for on OLTC is very low. The Bang Energy is 1/2CV^2 so with a low V we need a very large C to get a resonable energy. In order to tune it with a large C we need a small L.
Beware that the Q of the primary is SQRT(L/C)/R. If L is too small or R is too large the primary will not ring.
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First OLTC where to start?
