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Current in the Coil - was oil dielectric

Original poster: "David Thomson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>

Hi Malcolm,

>Agreed about the heating caused by current, but the current flowing in the
wires of an air-cored transformer can easily be in the tens of Amperes
range. Depends how much energy you feed in doesn't it? There must be few
Tesla Coils out there with a milliamp or less flowing in their windings at
some point or another.

The transformer I'm using is a 15KV NST at 30mA short circuit.  The
transformer is rated for 250 watts.  If I'm getting the full 15KV and the
power output does not exceed 250 watts, then the average operating current
can only be 16.7mA.  If the primary has only 16.7mA, then with the 50 feet
primary and 2000 feet secondary I should have a rough 1:40 step up ratio.
At 600KV the secondary will have an average current of about .4mA.  Even a
power supply of 1000 watts will only output about an average 1.6mA in the

Keep in mind that my coil has a flat spiral winding in the bottom quarter of
the secondary.  Flat spiral coils can handle tremendous current loads with
no heating to the windings, transformer, capacitors, or spark gap.  By the
time the electrical energy is in the solenoid and getting its voltage
increase, the current is not high enough to do any heating.  Hence the coil
runs cool even without being jacketed in oil.

The reason for the oil jacket is to keep the voltage in the coil, which it
does to perfection.  This system is state of the art as far as efficiency
goes.  The problem I'm having is that the coil is so efficient that when
tuned to output streamers, the streamers break out evenly over the surface
of the terminal, instead of as one long streamer.  So instead of getting one
8 feet streamer, I'm getting 8 one foot streamers.  When the system is tuned
to perfect resonance, there is no spark coming off the terminal even with
all the top load removed.  But the EMF field is very strong and tubes light
bright 5 to 8 feet from the secondary.

Another noticeable effect of resonance with a jacketed coil is that there is
a very intense electrostatic field around the solenoid.  It's almost like
touching a wall of electricity about one foot out from the coil form.

Point me to a Tesla coil that claims tens of amperes in the secondary.   I'd
like to check it out.  I'm sure that's just the peak current near the base
of the coil, but even still that's pretty high and would require a fairly
large system.  I don't think that is what Paul was intending to build.

In my opinion, every serious coiler needs to build at least one oil jacketed
coil.  They're not that difficult and the rewards are better sparks.