[Prev][Next][Index][Thread]
43" First light! - Dead Transformers :-(
Here are the stats for our first coil. I have several questions.
3-15kv 30 ma NSTs
0.028 30KV Pulse Discharge Cap - Surplus
Primary - 8 turns 1/4 fridge tubing, angled up at 15 degrees
Ground - ~10' heavy copper clad steel rod, #4 stranded wire
Secondary - 8.4" SDR35 Sewer Pipe, 45" long, 1500 turns #22, 1/4 wave freq
77.5
Khz
Corona Shield - 36" across, 7" cross section, flex heating duct and
aluminium tape
Spark Gap - Single gap set at ~1/2" Made of 1/8" brass fittings. There is
a flat
square plug with a small hole drilled in it facing a round plate. A 1/2
horse air
compressor is kept busy blowing air through the small hole. Lots of force and
flow.
After tuning the primary and adjusting the spark gap we achieved 43" sparks
to a
grounded rod. This was with the base of the primary aligned with the base
of the
secondary.
How much better performance should we expect to be able to get from a
15KV/90ma
supply?
We then tried raising the primary to adjust coupling. We seemed to get better
sparks but we got several strikes from the secondary to the primary. We
also got
one bright arc across the full 45" of the secondary from the ground
connection at
the bottom to where the toroid connected at the top.
When we shut the coil down at the end of this session it was working fine.
However the next day it would not work. It appears that at least 2 of the
NSTs
were damaged. We did have a protection network in place but it was poorly
constructed and "blew itself up". We had been operating without it when we
got
the primary/secondary strikes. Impatience :-(
I am looking for suggestions for a good protection system for this coil. I
will
have 4 more NSTs available so I should be able to operate with 4-7 (120-210ma)
depending on how many I can repair. I am considering unpotting them and
puting
them in oil.
I am also looking for general suggestions on solving the self strike
problem and
increasing the performance of the coil without destroying it.
The gap appears to be working reasonably well. We had a scope hooked to a CB
antenna. The gap was firing once per 1/2 cycle. There was so much noise
on the
scope that it was hard to tell how well it was quenching. We will be
working on
the instrumentation, maybe a current transformer on the primary. The coil
performed much better with the air on so that seemed to help quenching.
Tony