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RE: PVC Wire for a secondary?
Is the spark length increasing through the air becoming laden
From: Tesla List [mailto:tesla-at-pupman-dot-com]
Sent: Tuesday, June 13, 2000 3:07 PM
Subject: Re: PVC Wire for a secondary?
Original Poster: "Malcolm Watts" <malcolm.watts-at-wnp.ac.nz>
On 12 Jun 00, at 16:07, Tesla List wrote:
> Original Poster: Tesla729-at-cs-dot-com
> Hi John, Ed,all,
> Regarding PVC insulation, from my personal coiling experience, I have
> to agree with Ed Wingate's comments about using tight wound mag-
> net wire secondaries. If the system is properly tuned to the 1/4 wave
> length, the Vmax will only occur near the top terminal capacitance of
> the resonator while maximum current will occur -at- the grounded base.
> Remember, the (I) and the (V) are 90^ out of phase. Also, a good-sized
> toroid produces an elecstatic shield around the upper portion of the
> sec, where most of the very high potentials are located.
What exactly do you mean by "tuned to the 1/4 wave length"? The
secondary, being a 1/4 wave resonator always resonates most
strongly at its electrical 1/4 wavelength doesn't it? You surely can't
be referring to the length of wire in it can you?
> I have had experience with both space wound and tight-wound secs,
> and either will work if the system is properly constructed and tuned.
> It seems to me that it is advantagious to wind the sec. as tight as
> possible as this increases the (L). My current largest coil system is
> powered by a ballasted 10 kVA pole pig at up to 9 kVA, and the sec
> coil is 12"x 39 1/2" long and topped with an 8"x32" dryer duct toroid,
> and it can easily hurl 8 to 10 ft lightning bolts with no secondary
> flashover. And this is a classic two-coil system and not a "maggie".
Does that prove that that is the best you can do at that power level?
Not being pedantic but I think it is reasonable to ask for some kind
of benchmark to balance that coil against. It is known that topload
size influences sparklength also as does primary Q.
> Well, that's my observations just from practical experience. Its still
> a mystery to me to this day how a Tesla coil can produce sparks
> several times longer than the sec coil itself, but I know from experi-
> ence that under the right circumstances, it certainly can.
That is a clear indication to me that output voltage is insufficient to
flashover the length of the secondary. It is well known that sparks
stretch through repetitive firing. You can prove this easily - just run
the break rate up from 1 per second to whatever. Output voltage
doesn't increase but sparklength does.
> Keep on Sparkin'
> David Rieben
> Memphis, TN, USA