The Next Coil
From: Greg Leyh[SMTP:lod-at-pacbell-dot-net]
Sent: Monday, July 28, 1997 3:25 PM
To: Tesla List
Subject: The Next Coil
An opportunity has finally arisen to build a new coil from scratch,
and hopefully benefit from all of the mistakes and discoveries made
since my last coil design attempt, in 1990. Seven years is long enough!
Based on countless bits of information exchanged with people on the List,
numerous PSPICE simulations, and many past mistakes, here are some values
from the preliminary design set for the new coil:
Top Capacitance - 130pF (96" OD space frame sphere, 28' altitude)
The top C is where this coil design starts. I have finally bought into
the 'huge top C' argument, after reading more about the microsecond
structures present in lightning as the spark front advances. Even though
the top C reduces the Vout directly, it appears that a local low-Z
reservoir of charge must be present at the base of the streamer channel
in order to solidly support the streamer growth on microsecond timescales.
Adding a physical 100pF capacitor to my existing coil proved this out.
-- Preliminary Design Values --
Lsec = 120mH (37" X 154", 5 turns/inch)
Fsec = 51kHz (no sphere) 36kHz (w/sphere)
Cpri = 0.270uF (0.045 X 6 units)
Vpri = 44kV
Coupling = 0.22
Max Break Rate = 400 BPS
HVPS Capacity = 120kW (3PH to DC, resonant charger)
Preliminary construction and testing of components is ready to begin, at
a site inside the Hunter's Point Naval Shipyard, in San Francisco. This
location was selected for its abundance of cranes and electrical power,
its high level of security, and its remoteness from residential areas.
I will post results and pictures as they become available.