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New Tesla Book


RE: HIGH VOLTAGE GENERATION WITH AIR-CORE SOLENOIDS
written and published by Thomas W. Lee, 8329 E. San Salvador Dr.
Scottsdale, AZ  85258  USA
 
> The example of a "high-performance" coil system uses a machine
> shop nightmare of two nested acrylic tubes. The secondary 
> winding is on the smaller inside tube, the larger diameter 
> outside tube keeps the winding submerged in MINERAL OIL! 
> (Polyurethane has it's disadvantages but...)
 
 JO> Where does the polyurethane come in Richard ?

Well the whole idea of the two nested acrylic tubes and
submerging the secondary winding in oil is to increase the
breakdown voltage of the construction and to eliminate corona
losses.

I have verified that corona losses can be reduced to acceptable
levels by coating the secondary coil with enough heavy coats of
polyurethane sealer that the ridges and valleys of the magnet
wire winding are eliminated, followed by loading the coil with
the proper sized toriod discharger. 

 JO> Was there any rationale for all this complexity ? 

The author's rationale apparently is to compensate for a coil
design that was overwound with too many turns of wire that is too
thin. In addition, the author was still advocating small sphere
dischargers as opposed to large toriods.

The large number of turns creates a large self capacitance in the
winding that delays the current peak in the coil. The long thin
wire has a high DC and RF resistance which further weakens the
current peak developed in the coil. A sharp current peak in the
coil is essential in obtaining a long hot spark.

Using a small sphere discharge terminal does not corona protect
the secondary winding very well. As you saw in the pictures of
Malcolm's coil, many good sparks, and lots of corona, will leave
the system from the sides of the windings if the coil is not
properly loaded with toriod. Oil submersion reduces these losses.

Also, a coil constructed with a lot of turns of very thin wire
will easily overcouple and "split" into parasitic 1/4 wave
resonances: sparks will breakdown turns and shoot down the coil
sides. Oil submersion will electrically strengthen the coil. 

The author's solution for such a poorly designed coil is to
engineer the problem away after the coil is wound. By sumberging
the secondary in mineral oil, so that the winding has about one
inch of oil all around it, excessive corona losses from the
windings are reduced to nearly zero. Mineral oil prevents
parasitic 1/4 wave voltage peaks from breaking out of the sides
of the coil, and gives sufficient electrical strength that most
turn to turn breakdowns are eliminated as well. The coil can then
be coupled closely to the primary despite the poor design. By
close coupling, some of the current peak lost in the poor design
may be regained.

 JO> What is the claimed performance ?

Let's just say that it is about average. The coil will be able to
produce discharges that exceed the physical length of the winding
without breaking down. If properly loaded with toriod, the coil
would be capable of excellent performance most likely, provided
it is coupled to the correct primary. This performance comes at a
very high cost in materials however...

Richard Quick



... If all else fails... Throw another megavolt across it!
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