[Prev][Next][Index][Thread]
Re: My new coil
Tesla List wrote:
>
> Subscriber: Esondrmn-at-aol-dot-com Thu Feb 13 22:06:55 1997
> Date: Thu, 13 Feb 1997 18:26:05 -0500 (EST)
> From: Esondrmn-at-aol-dot-com
> To: tesla-at-pupman-dot-com
> Subject: Re: My new coil
>
> In a message dated 97-02-13 04:18:08 EST, you write:
>
> <<
> I have just recently completed the construction of my second coil.
>
> The coil consists of a 10" secondary wound on HDPE pipe 950 turns of
> 1.02mm enameled copper wire. The secondary consists of 11 turns of
> 3/8"
> copper pipe, capacitors are home made poly/foil construction 0.03uF.
>
> Powered by 11KV 5KVA single phase pole transformer using a home made
> rotary spark gap based on a brush type motor with top speed of 15,000
> rpm.
>
> The toroid is pathetic, being the same diameter as the coil, I
> could'nt wait to try the coil out so last week end I fired her up.
>
> The first time of firing this coil was also the first time of using a
> pole transformer, so I thought it best to do things slowly!
>
> By turning to rotor on the gap so that two electrodes aligned I powered
> the
> coil up using a variac. At about 10% the gap fires, and soon becomes
> red
> hot, not much good for coil firing but OK for tuning up using a
> flurescent
> tube. Having found a good tune (turn 9), the rotary gap was started at
> low
> revs.
>
> With more power being applied to the pole transformer large bangs and
> rough
> coil running the variac began to smoke and fuses blew. 12" sparks for
> the
> top of the coil - went to bed.
>
> Using a pole transformer for the first time was scarey! Good job I had
> practiced on a neon transformer first. I always unplug HV supply when
> making
> adjustments even if the variac is at 0%. I got a nasty shock from my
> neon
> when supply still connected and variac at 0%. I later measured the
> output
> of the variac - it was 2 volts, stepped up through the neon made
> 150volts.
>
> With a fresh mind the next morning I repaired the variac (stuck brushes)
> replaced the fuses, and used a 100 meter extension lead as resistive
> balast.
>
> This time I ran the spark gap at
> about 40% and coil at 40%. Things ran much smoother, no banging, and
> no
> blowen fuses. Getting 2' arcs. Increced power to coil to 100%.
> Sparks
> now up to 3'. Increaced power to spark gap to 80%. The spark length
> increaced significantly 4-5' the color of sparks changed from purple to
> white/blue, noise increaced (need ear protection) - must be getting
> better
> quenching from the gap as speed increases.
>
> Then desaster! Vibrations on the spark gap cause the electrodes to
> strike
> shatering the rotor and bent the stationary electrodes. Pieces of
> spark gap
> shot across the garage.
>
> After re-building the sparkgap (better desgn this time) I can not get
> longer
> sparks than 4-5'. Partly because the ceiling of the garage is in the
> way.
> Everything is being run at 100% power now.
>
> Things I plan to do to increase spark length:
>
> 1) More electrodes on the rotary spark gap. Currently 2 increase
> to 4
> 2) Build a toroid
> 3) Add more capacitance to the tank circuit in order to match new
> secondary resonance when new toroid fitted.
> 4) Connect second pole transformer (5KVA)
>
> Any tips on getting better/longer sparks are very welcome
>
> Julian Green
> >>
>
> Julian,
>
> Congratulations. Sounds like a winner. I did some quick calculations on
> your system. Secondary inductance should be about 49 mh, self capacitance
> about 18.8 pf. It should resonate at about 134 khz with a 10 pf toroid. If
> the primary is 12" I.D., it should be about 72 microheneries. The math says
> it should tune about turn 9 right now. You should be able to go up to almost
> 30 pf in toroid capacitance and still just barely tune at turn 11. This
> would be about 100 khz. Using the 80% rule (lose 20% of the toroid
> capacitance for shading), you should be able to go up to a 35 to 38" x 5 or
> 6" toroid with your present capacitor.
>
> I would definitely get some inductance for ballasting. As you found out,
> with no ballast, a pig wants to draw infinite current. Your added resistive
> ballast certainly helps but they are hard to control with no inductance. I
> use a welder on mine and set the current low (about 10 amps primary current)
> for tuning then turn it up when everything is set. Even then, there is still
> some inductance in the system. I don't remember the exact number but I think
> it is around 5 mh with the welder wide open and the welding leads shorted.
>
> Your secondary can certainly handle a much larger toroid and it should
> perform very well with a toroid as I described or maybe even up to 40 or 48"
> with more capacitance. Is it possible to add a few turns to your primary?
> This may be easier unless you have more caps available. With 11 kv in, you
> may get to where the toroid is too big to break out and would require higher
> voltage in.
>
> Ed Sonderman
Wow, I'm sorry for your rotor breaking, but you were getting 4-5'
withoug a toroid?!? Amazing. Got any photos of this?
You got alot you are adding, have fun, and protect yourself (Mainly from
the flying rotors ;).
I'm currious if you have a safety gap (Well, I'm sure you do), and did
it fire like crazy when your rotor broke? Did this melt down the safety
gap or did you catch it quick?
I gotta see this, next run, please please grap some pictures!!
Jeremy Bair