# Concerning Peter's DC Drive

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From: 	Larry Robertson[SMTP:LWRobertson-at-msn-dot-com]
Sent: 	Wednesday, July 16, 1997 8:22 PM
To: 	Tesla Builders
Subject: 	Concerning Peter's DC Drive

Hi Folks

I also have been thinking for a while that a DC drive would
be not only more efficient, but would also make the rotary gap
completely uncritical as to speed, up to maximum power delivery.

As I was contemplating on how to get the small resonance cap.
recharged, I thought that we use a pulse discharge already,
so why not pulse charge it as well. If the large cap is big
enough compared to the small cap., having them in series from
the point of view of the primary coil should not change the
resonant frequency much. For instance, if the small cap is
0.02 uf and the storage cap is 1 uf, when viewed in series
the capacitance is 0.0196, not much of a difference.

The diagram below might actually be legible if viewed with
a monospaced font, such as "QuickType Mono" which I used to
make it.

Think about a rotary gap consisting of two poles rotating,
and four poles stationary. Two adjacent stationary poles are
connected together, and go to the resonance cap. The other
side of the resonance cap goes to one side of the primary
coil, the other side of the primary goes to a common which
I'll call ground. The two remaining stationary poles go to
the HV end of the storage cap, and to ground, respectively.

As the gap rotates, the resonance cap will be alternately
charged from the storage cap, and shorted to ground. The
primary coil will alternately see the small cap and large
cap in series with it, then just the small cap in series,
but with opposite polarity.

Rotary
------
v     |  Small
+ ------ RFC---------o-------->     <--o-  CAP ----
>From                      |           ^                 |
Diode                   Large         |              Primary
Bridge                   CAP          |                Coil
|           |                 |
- -------RFC---------o-----------o-----------------

I think a diode bridge would make most efficient use of the
transformer.

I've already built one diode, consisting of 35 1N5408  3 amp
kV diodes in series, each one with a 1 meg. resistor and a
0.001 uf cap across it for equalization. I put all these
on a piece of plexi, and covered it in mineral oil in a
Tupperware container.

It takes the output from two 60 ma 15kv neons in parallel
with no complaint, but I still need a storage cap. A
suitable resistor between the diode bridge and the RFC's
might also be a good idea.

What do you think?

LR

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