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H-Bridge DC drive.
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From: L.Robertson [SMTP:LWRobertson-at-email.msn-dot-com]
Sent: Monday, March 23, 1998 1:37 AM
To: Tesla Builders
Subject: H-Bridge DC drive.
Hi folks ...
I just got my H-Bridge drive working. As posted earlier,
this consists of two 15 kV 60 ma neons in parallel, a full
wave bridge, considerable RF filtering, and feeding into
a 1.8 uF 60 kV capacitor. A rotary spark gap charges two
0.05 / 50 kV caps in an equidrive Tesla circuit alternately
positive , then negative through the big cap.
I now have independent control of break rate and power,
from a pulse every couple of seconds to 240 BPS,
from not breaking out at all to 24 inch single shots.
Performance is way up - I now get similar spark length
at half power, without resonant charging, than I had before
at full power as a classical AC coil. As break rate goes
up I have to increase power to achieve the same spark
length, but not nearly as much as you might think.
It is interesting to watch the difference in the spark as
the break rate is ramped up. At low rates multiple short
sparks break out all around the torus. As the rate increases
the spark tends to coalesce into longer, more intense
streamers with less branches. Finally it makes one big
streamer that searches around looking for something to cook.
As the streamer comes close to any ground point, corona
starts to drip off nearby metal, and football shaped
purple corona connects the torus and the object of it's
desire.
Much beyond half power on the variac, MOV's on the
power line start to blow up like smelly little candles, also
blowing the breaker. The power line is so far removed
from the action I can only conclude induced currents
must be responsible. The neons, diodes and filters all
seem as happy as can be.
I just got 60 inch sparks straight up. (does that count? )
48" is about all I have horizontally, but that is where the
walls are and connected sparks happen at random
every few seconds.
LR