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Re: The Next Coil
From: Greg Leyh[SMTP:lod-at-pacbell-dot-net]
Sent: Thursday, July 31, 1997 4:49 PM
To: Tesla List
Subject: Re: The Next Coil
Peter Electric wrote:
> Is there some reason you chose a sphere over a larger diameter toroid?
At that size spheres are easier to build, and I also wanted a geometry
that could accomodate a human observer. The arc departure points can be
positioned by applying small 'whiskers' on the top electrode.
> Also I have been planning my next coil as a DC system for some time but
> how do you rectify 130Kw?!! Do you believe DC Tesla coils are inherently
> more efficient?
The rectifier array consists of six stacks of diode modules, with the
stacks arranged in the standard 3-phase to full-wave DC configuration:
O-------------O-------------O--------- +
| | |
stack stack stack
| | |
PHASE A--O PHASE B--O PHASE C--O HVDC OUT
| | |
stack stack stack
| | |
O-------------O-------------O--------- -
Each rectifier stack consists of 12 UDE5 'doorbell style' diodes in series,
rated at 5kV, 5A each, for a total per-stack rating of 60kV at 5A. These
diodes feature internal snubbing networks, and seem quite rugged -- not a
single one has failed yet on my previous coil. At 120kW the RMS current
_per stack_ is less than 3A, for 12kV phase-phase mains.
I do believe that DC Tesla coils are inherently more efficient for two reasons:
A) Better power factor
B) With DC, _every_ firing of the primary ckt is at full energy, keeping
the streamers continuously ionized
-GL