You can see the interrupter box, in the bookcase, in the middle of the pic (with a big 2.2 uF cap on it and the pots).
The differencies between my setup and Steve schema are minor:
- separate interrupter circuit, connected with the driver through a coax cable.
- 470 uF @ 400 V electrolitic cap on the bridge, instead 420 uF
- MUR 3060 for FETs protection instead MUR 880 (thanx Adam).
- 1 uF @ 630 V caps on the cap divider of the bridge instead 0.68 uF
- 12 turns windings on GDT instead 16
- 18 V @ 1 watt Zenners on the FET gates.
- I added 1N5819 diodes on the UCCs output to clamp to the +/- rail voltage.
- longer antenna ( approx 30 cm)
- separate AC/DC source (12 V @ 1000 mA) for logics
- 3 turns primary coil, wound at the bottom of the secondary instead 4 turns as Steve has.
- 11 cm/ 28 cm, 966 turns secondary, freq = around 400 kHz without toroid.
I used first time some IRFP460A (500 V @ 20 A) in a half bridge, but they exploded violently at 220 vac input, full rectifyed, when I tryed to draw some arcs to ground and the heatsinks got hot. I moved to IRFP260N (200 V @ 46 A), half bridge, on some big heatsinks and all the problems just vanished. I know that I am limited to max 120 vac input from my variac, but the reliability of the system compensate the shorter spark lenght. Even so, I managed to get up to 8 inches streamers at 110-120 vac input, full- rectifyed, no primary cap. |
