Re: OLTC II Initial calculations

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <teslalist-at-qwest-dot-net>" <FutureT-at-aol-dot-com>

In a message dated 5/6/03 8:05:57 PM Eastern Daylight Time, 
tesla-at-pupman-dot-com writes:

Steve,

In some tests, I pushed my 4.2" x 23" secondary to give 61" to
63" sparks at 120 bps.  There were occasional racing sparks
especially when giving 63" sparks.
A  6.5" x 24" secondary also gave racing sparks under the same
conditions.  The coupling was relatively loose at anywhere between
k = 0.08 to k = 0.10.  When I turned down the power to give 58"
sparks, then there were no racing sparks.  This coil had a tendency
to give racing sparks because once the secondary breaks down, it
breaks down more easily in the future.  I used a 6" x 26" ducting toroid.
The secondaries used 1500 to 1700 turns of 28awg wire.  I would make
the secondary at least 24" tall for 120 bps and a 58" spark length.

My guess is that your low resonant frequency will work fine.  But a
little higher frequency would let you use a little narrower secondary.

John


>Secondary:     10" x 20", 1500 turns
>Toroid:     6" x 20"
>
>Resonant freq:     65.3kHz
>
>Bang energy:     10J
>Peak primary current:   4100A (2050A/brick)
>Top voltage:     625kV (if lossless: 450kV if 50% efficient)
>
>Output -at- 120bps:   58"
>
>I have a question for the more experienced tesla-teers on the list. I heard
>there is a relation between the top voltage and the secondary length i.e.
>if the secondary is too short for the voltage it will flash over and be
>ruined. What is that relation, and do you think I am the wrong side of it?
>I'm a bit uneasy given that if you apply the 1.1kV/mm rule, the sparking
>distance for 625kV is 27" which is longer than the secondary! Plus, I don't
>want to be striking the primary/control box too often. I could easily make
>the secondary taller/thinner if I have to.
>
>Another thing, do you think the resonant frequency is too low? I heard that
>streamers don't grow so well at low frequencies. Again, I could probably
>raise it a bit without running out of peak current.
>
>Any input much appreciated,
>
>Steve C.
>
>