RE: [TCML] Rectifying a Tesla coil

["Aron Koscho" <kc5uto@xxxxxx>]

Justin Hays and I rectified a TC about six months ago. Here are the
specs of the coil:

DRSSTC
4" x 16" sec
3" x 12" toroid
73nF tank cap
~180KHz operating frequency
Nominal discharge without diode - 24"

The diode was an array of 50 20KV 20nS Ultra Fast Avalanche rated diodes
(sorry don't remember the P/N). The array was placed in a 1" PVC tube
filled with mineral oil. The tube was suspended by a nylon cord from the
rafters in the shop. One end was connected to the coils 3" x 12" toroid
and the other (positive) end was connected to a 6" x 24" toroid.

Upon applying power the coil would be briefly loaded than break out as
normal. First I found this odd but it makes sense; the coil was unloaded
after charging the larger toroid. The DC arc was about 8-10" long to a
1.5" x 6" toroid connoted to ground through a 6M resistor. It would
charge EVERYTHING in the vicinity.

After power was shut off the pipe covering the diodes as well as the 6"
x 24" toroid would remain charged until grounded out. We were able to
experiment with the device for a total run time of about 10min before
the diode failed. We believe this was do to unequal voltage distribution
along the string, most likely caused by the large capacitance to air of
the tube they were housed in.

We have not duplicated the experiment since but I am confident it is
easily repeatable. I think Justin has some pics of the setup but it
really is as simple as I described it.

Aron




-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of Peter Terren
Sent: Friday, August 29, 2008 10:00 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] Rectifying a Tesla coil

I would answer no.
I don't know of anyone who has rectified 200kV plus from a TC. Diodes at

100kHz will need to have a very fast recovery and avalanche capability.
They 
are not readily available. I have about 50kV worth of 9ns ultrafast
recovery 
diodes but they don't avalanche so I would be risking all.
The point and plane method has not worked for me. I have used multiple
point 
and concave surfaces and an electrometer to determine DC charge. It only

rarely resulted in DC which would leak away rapidly. Of course any spark

that connected would short circuit the diode so it is a corona device
only.
Of course, even if you could rectify a TC giving a 6 foot spark, you
would 
only get DC with a 1-2 foot spark since you don't get the spark growth
with 
DC.
Perhaps I should try with my big TC which has a resonant frequency of
39kHz 
which is getting down to the region where my 1MV string of (non fast 
recovery) HV avalanche diodes might work.

Peter

----- Original Message ----- 
From: <Sfxneon@xxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Saturday, August 30, 2008 5:02 AM
Subject: Re: [TCML] Rectifying a Tesla coil


> In a message dated 8/29/2008 1:52:22 P.M. Central Daylight Time,
> jhowson4@xxxxxxxxxxx writes:
>
>>Is it possible to rectifiy a Huge tesla coil?
>>No reason I  was just curious.
>
> A simple, but not too efficient method to rectify the output of a
_large_
> coil might be the "point and plate electrode" type of rectifier where
a 
> pointed
> metal rod is aimed at the center of a round metal plate, close enough
for
> ionization to take place. Some rectifying action takes place due to
the 
> geometry
> of the electrodes, and a high DC potential can be accumulated. I'll
bet
> Jeff at Electrotherapy Museum has some examples of this being used for

> early
> x-ray tubes, huh Jeff?
>
> Tony Greer
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