# Solid state Secondary

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From: 	Alan Sharp[SMTP:100624.504-at-compuserve-dot-com]
Sent: 	Sunday, January 04, 1998 9:26 AM
To: 	Tesla List
Subject: 	Solid state Secondary

-------------Forwarded Message-----------------

From:   Alan Sharp,
To:     INTERNET:tesla-at-pupman-dot-com, INTERNET:tesla-at-pupman-dot-com

Date:   03/01/98 20:43

RE:     Solid state Secondary

>I have finally finished coating my secondary for the solid state coil.
>The coating is Bher build 50 super gloss. I used two coats to ensure
>corona is suppressed. It is very high gloss, and seems to be very tough.

>  Coilform: a cylindrical ice chest shaped EXACTLY like a Pepsi can!
>  Diameter: 12.54"
>  Length: 18"
>  Wire Gauge: #21
>  H/D: 1.44

>  The first 2.5"(at the bottom of the coil)is tapered down to 11". I
>wonder how this will alter the operation of the secondary?

Sounds great - should perform well. My secondary is wound
on a polythene bucket - it does fine - no worry about the tapering.

I've been going over Bylund's comments on secondaries.
He shows that you get maximum inductance for a given length
of wire when the hieght = 0.9 * the radius. This doesn't make
for practical coils.

I plotted indunctance against hieght/radius for different
lengths of wire and different diameters. The graph was always
the same shape. From the graph.
Inductance = Max 100% when h/r = 0.9
90% when h/r = 2.2 (or 0.4)
80% when h/r = 3.6
70% when h/r = 5.4
60% when h/r = 8.1
50% when h/r = 12.5
40% when h/r = 20.5

Your h/r gives 85% of theoretical maximum inductance which is fine.

Bylund also gives the equation for output voltage

Vout = Vin / R * sqrt(L / C)

Thus like you I chose to maximise L and minimise R.

But Bylund also comments that the losses in the coil
are as nothing compared to Corona losses -

My question is this could we do just as well winding
2000 turns of 32 guage wire onto a 4" drain pipe or
whatever gives the same inductance.

Have fun,

Alan Sharp (UK)

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