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Rotaty popping, (Was Re: commercial cap failure)
<snip>
>
> If you had a safety gap across the cap, I would think that you did not
kill
> it with overvoltage. What is the gap width set to? What are you using
for
> ballast for the pole transformer? When I was having this problem, the
sound
> coming from the rotary was not nice and smooth, there was frequent odd
noises
> that sounded like small explosions or backfires - not exactly, but I don't
> know how else to describe it. When I changed the ballast from the welder
to
> a large variac, this all went away.
>
> Ed Sonderman
>
>
Ed,
Jon Rosenstiel here. We corresponded a few times via email, ( Re:
Sonderman's Saga). Your above comment in regards to explosions or backfires
in the rotary made a light go on. With my system, (6" x 28" secondary, 5kVA
14400V pig and 120bps srsg), I notice every once in a while, (particularly
above 230Vac in), a sound like a car door slamming shut. I usually shut down
and check for visitors, but never find any!
Other than the infrequent car door slamming sound my coil runs fine, always
nice and smooth, but I have this nagging feeling that something's not
quite right. I think that I'm getting too much "inductive kick" from my
welder ballast. The reason's that I think I'm getting too much "kick" is
that:
1. Any amount of parallel resistive ballast kills coil performance.
2. Coil performance is better with the welder on "low" range. Let me
explain; The welder that I'm using for ballast is a old Sears 185A model
that has a low and high current socket on the front panel, (along with the
variable inductance core). I would think that I would be able to input more
current, (and get longer sparks), using the high range socket. This is what
happens when a Jacobs ladder is connected. I figured the same would happen
with my coil connected. It doesn't. My coil has best output on low range.
When I select high range the input current stays the same and to get the
same sparks I have to turn up the input voltage.
I think that next time I run my coil I'll install a safety gap across the
srsg and observe the firing of the safety gap while trying, 1:Parallel
resistive ballast, and 2:Low and high range on the inductive ballast,
(welder). I think that if I'm getting a lot of "inductive kick" the safety
gap across the srsg will fire easier, (or more often).
I will also try to watch the srsg closer to see if I can see any flashes of
light associated with the "car door slamming" sound. With 6' sparks flying
around it's pretty hard concentrate solely on the gap. Maybe I need to have
my coiling buddy come over so there are two of us to observe things.
I'm chicken to wire the safety gap across the cap because when I once did
the cap failed just as the safety fired.
Maybe a coincidence, but I'm not pushing my luck!
Regards,
Jon
PS: What is the current rating of your current control variac? 28A? Or
larger?