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Six inch coil & SRSG
Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Esondrmn-at-aol-dot-com>
Well, I finally got my six inch coil set up and tested last night with the
new synchronous rotary spark gap. Primary cap is .050 ufd, 5 kva 14.4 kv
pole pig balasted with a 5,000 w Luxtrol dimmer variac with a 1,000 w 1.6 ohm
resistor in series. It runs very good, massive sparks everywhere, even
hitting the cement driveway. John, the phase control system works great. I
wouldn't even like to run this coil without it. I found the 240 bps position
on the phase control variac and also found the 120 bps position. At 240 bps,
there is an intense blue corona field that forms from the top of the coil to
the outside of the primary, looks like a Christmas tree. At 120 bps, this
field is more intense and I was afraid to run it very long here because I did
not want to destroy the secondary like I did on my small 3" coil when testing
this spark gap. The bottom turn of the secondary is just about even with the
flat primary. I will need to reduce the coupling and try it again at 120
bps. I really did not see any difference in spark output at 120 vs 240.
Bill Wysock, the rotary works great, thanks for your work.
I tried shorting out the 1.6 ohm ballast resistor and the spark gap starts
popping and the system runs very rough. It did not like that. I was able to
get up to 30 amps primary current into the pig at just over 250 volts -
should be about 7.5 kva. Even blew the 30 A breakers down stairs for the
first time. Max spark length was the same as with the async rotary gap which
is 104". Has anyone beat this length with a 6" secondary?
After getting some experience, it was easy to find the 120 and 240 bps
points. You can tell by the tone and by feeling the rotary contacts after a
run. At 120 bps, only two of the four contacts get hot. At 240 bps, all
four get hot. After about a two minute run, the contacts are very hot. Hot
enough to burn your fingers. I do have an additional cooling fan mounted on
the box that covers the rotary. I had my safety gaps across the rotary set
at .45" and they never did fire.
All in all, lots of fun, it has been quite a while since I have run this coil
at full power.