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Re: My new coil

>Date: Wed, 12 Feb 1997 12:30:00 -0500
>From: Julian Green <greenj-at-swlogica.demon.co.uk>
>To: tesla-at-pupman-dot-com
>Subject: My new coil
>
Welcome back Julian!

[snip]
>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 the rotary gap stationary, there is no air flow over the
electrodes to cool them.  Also, try a multielement static gap in
series with the rotary gap to help it quench.
>
>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.

You do not have enough ballast reactance to limit the current through
the pig. 

12" sparks from the toroid, how long were the sparks from your poor
variac?:)
>
[snip]

>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.

Try this:  Connect your resistive ballast to your pig's primary. The
pig's secondary to your cap and rotary. (all in parallel) Leave your
TC elsewhere. I was able to cause my rotary to flame a complete circle
using this ballast test! This shows 2 failures: bad quenching in the
rotary gap and not enough inductance in the ballast.  As soon as I put
in 9mH of inductance (home wound) into my pig's primary circuit, the
rotary flame stopped and was replaced by a very loud, smooth spark!
>
>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.
>
Better!

>Then disaster!  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.

Next time add a "BLAST" shield to protect you from flying debris and
try your rotary out without any HV applied.
>
>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.

Ah Ha! can't say "more power" you now have to say more room! At this
point in my TC work, I built a roll-arround base for it so that I
could move it outside of my garage.
>
>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.

Good

>4)      Connect second pole transformer (5KVA)

Halt! before you add another pig, 

	(you can run your 5kVA unit up to 10kVA or 15kVA for short 	
	times {several 10s of minutes is a short time for a pig:)

tweak all the other parameters in your system and add some inductive
ballast in your pig's primary circuit.  The inductive spike that
occurs in this ballast, when the spark gap quenches, will help charge
your TC's primary cap faster resulting in much longer arcs. When you
add inductive ballast to the primary circuit you must also add some
PFC caps or Motor start caps across the line to prevent this inductive
spike from traveling into your house mains and blowing things. (like
the RFI filters between it and the house mains;)

	cheers,

	jim