To: <amps@contesting.com>
>Date: Tue, 6 Jul 1999 22:20:14 +1000
>From: "cd" <bearl@ozemail.com.au>
>Subject: [AMPS] professional rectifiers/equalisers
>With all this talk about the pros and cons of rectifiers what do the =
>professional broacast transmitters use?. What about John Lyles K5PRO he =
>must have some interesting high voltage sticks laying around for some of =
>his projects. Likewise the Los Alamos labs certainly would have some =
>huge rectifier sticks for there purposes. Anyway i have the Voltage =
>Multipliers Inc catalogue here, and they do the same as Rich suggest =
>strings of series diodes without any resistors or Caps, they do seem to =
>pot them however. They sell these sticks up to 20 KV 6 amps but want =
>silly prices for stringing diodes together.
>
>Craig=20
>VK3HE
A month or two ago, I submitted a long list to the AMPS mailing list, of
stick rectifier stacks. Maybe you missed it. Here is the archive on the web
to read it.
http://www.contesting.com/_amps/9904/0453.html
Certainly a lot of these sticks can be used in ham rigs. I have replaced
the discrete diodes in the SB220 that I run, with a pair of Semikron
avalanche modules, with no RC networks. They work great. Did this a few
years ago, when I looked inside an saw some nasty looking burnt diodes.
Yes, we have a lot of big rectifiers around work. Most of the ones I see
that are pulled out of their oil tanks are big stacks of International
Rectifier modules, on frames. They do have RC compensation, being rated for
up to a hundred thousand volts.
I have sitting on my desk a fried circuit board diode stack for an 18 kV DC
supply, made with twenty-six EDI 5 Ampere diodes compensated with 0.005
uF, 1 kV Z5U, and 1M 0.5 watt carbon comp resistors. 6 of them are burnt
beyond recognition. We believe that the power supply didn't shut off when
the crowbar shunted the output during a tube arc. The diodes are in a 3
phase bridge, 2 boards per leg in series. The AC stayed on, into a dead
short. It was inside a Universal Voltronics Corp. Power Supply.
The biggest rectifiers we have are used in a Cockroft-Walton HV DC
accelerator, which raises the energy (actually momemtum) of protons from 60
to 750 KeV. Diodes are used at 6 KHz, in a big voltage multiplier, to get
to 750 kV DC. The room is about 40 x 40 x 40 feet for this animal. There
are three of these rooms. You may have seen a video of it on Nova TV show
(PBS) or the UK Horizon channel show about Star Wars a few years ago. Each
diode stack must be 2 - 3 feet long, in a plastic tube, which is oil
filled. Inside are MANY series diodes, and RC comp assemblies I believe.
All proton accelerators used them at one time. Cockroft and Walton were the
British physicists that first accelerated particles with a DC column of
this sort. The voltage multiplier is just a scaled version of what is in a
color TV CRT power supply.
These days they are being replaced with Radio Frequency Quadrapole
accelerators. No one likes that kind of HV DC around, and they are tricky
to maintain and operate, especially at high altitude.
Gary, W3AM, has his nose inside broadcast radio TX, so his are probably the
state of the art as far as reliability and lowest cost for the performance
required in that service. $450 each, eh?
73
john
K5PRO
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