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RSG Idea, PSU Question
----------
From: Marco Denicolai [SMTP:marco-at-vistacom.fi]
Sent: Thursday, July 02, 1998 12:57 AM
To: Tesla List
Subject: Re: RSG Idea, PSU Question
At 23:06 01/07/98 -0500, you wrote:
>-----Original Message-----
>From: Ian Hopley <i_hopley-at-wintermute.co.uk>
>To: 'Tesla List' <tesla-at-pupman-dot-com>
>Date: Wednesday, July 01, 1998 7:59 PM
>Subject: RSG Idea, PSU Question
>
>Hi all,
>
>Been away from the hobby for a couple of years, family raising and all
>that, and although not coiling again yet I thought I'd catch up with the
>latest ideas. One of my problems when I last fired was that I popped the
>last of my transformers (unpotted NST's and oil ignitor's), and was
>contemplating using MOT's as the former are very rare beasts indeed. The
>problem I found was the risk of secondary-primary flashover if more than
>two secondarys were connected in series. Then I spotted in somebodys post
>that they were using a voltage doubler arrangement. I understand the theory
>behind the doubler and it would certainly solve a lot of problems, but it
>raises a couple of questions:-
I guess you refer to my tank design: here follows the schematics (without RF
filters)
and the measurements I made.
***************************************************************************
I had eventually a chance of performing a real measurement on the circuit
below. I used a digital scope and applied to the mains 3.5 VAC instead
of 220 VAC. After the measurements, I scaled up the results and these
I am reporting in the following.
| |
--------|| ||-----| |----*---------- V-
* || || * | | |
|| || -----
220V || || \ /
|| || \ /
|| || -----
|| || |
--------|| ||------------*--- GND
|
|
--------|| ||------------*
* || || * |
|| || -----
|| || \ /
220V || || \ /
|| || -----
|| || | | |
--------|| ||-----| |----*----------- V+
| |
Voltage V+ to GND oscillates between 6270 V and 0 (2200 VAC * 2 * sqrt(2) =
6270 Vpp).
Voltage between V- and GND oscillates between -6270 V and 0.
If the transformers are in phase, voltage between V+ and V- is almost DC at
6270 VDC.
V+ |----| |----| |----|
| |----| |----| |
GND ------------------------------ V+ - V- = 6.3kV DC
|----| |----| |----|
V- | |----| |----| |----
If the transformers are NOT in phase, the output is a sinusoid at 50 Hz
going from 0
to 6270 Vpp * 2 = 12540 Vpp.
V+ |----| |----| |----|
| |----| |----| |----
GND ------------------------------ V+ - V- = 0 to 12.5kV DC pulsed
| |----| |----| |----
V- |----| |----| |----|
I use the last configuration (transformers NOT in phase, 12.5kV pulsed output).
***************************************************************************
>1) Was this arrangement used with a spark gap or solid state switched
>system?
I use a RQ spark gap.
>
>2) What sort of current/ power o/p was available?
Depends on the MOT you are using. I use two 900W MOTs plus a third one
connected as
shunt (with its secondary shorted) on the 220V side.
>3) The voltage doubler arrangement gives a DC o/p and not much had been
>documented about the use of DC, will this require the use of a RSG as I was
>having very good results with an air quenched multi-gap powered by a vacume
>cleaner blower (sucker?).
As you can read above, with this design you can get either AC or DC, as you
like.
>
>4) Any sugested values for doubler Cap's and Diodes?
Caps straight from a microwave oven are OK. Never blown one. Diodes from a
microwave
oven are OK too, if you use a shunt like me and don't get strikes from toroid to
primary. After several hours of happy Tesla lightning I got one of those strikes
that killed one of the diodes. I am going to test in the next days with a series
of two microwave oven diodes, with resistive divider network to split
correctly the
voltage on them and 750 pF capacitors in parallel for protection. I will
also employ
a strike rail.
I have also got a double 3mH inductor and 550 pF RF filter on both wires
going to the
spark gap and primary capacitor.
Diodes and capacitors have otherwise performed very well. And I never got
arcing or
faults on the MOTs. MO diodes are typically 9KV 450 mA.
At today, with this MOT tank and a 4" secondary I can easily get 20"
streamers to a
grounded point.
________________________________________________________________________
Marco Denicolai Vista Communication Instruments, Inc.
Hardware Development Manager www.vistacom.fi
marco-at-vistacom.fi Kaisaniemenkatu 13 A
fax: +358-9-622-5610 SF-00100 HELSINKI
phone: +358-9-622-623-15 Finland
Remember, Murphy was an optimist! I am not...
________________________________________________________________________