Re: Saturable reactors?

On Thu, 10 Dec 1998 23:40:14 -0700 in the Tesla List
Tony Greer <NeonGlow-at-webtv-dot-net> wrote:

>Hi Bill, Marco, Scott, & coilers all!
>This "little-known-today" device known as a saturable reactor is
>still being used today in controlling neon tube bombarding
>transformers in the 7.5kva to 15 kva range. It is simply placed in
>series with one side of the primary, It is the most desirable (and
>expensive) method of doing so...

I have seen bombarder transformers controlled in three different
ways; the older ones used a variable reactor or choke that had a
longish iron core that you slide in or out of the coil to increase
or decrease it's inductance accordingly. Then there is the
saturable reactors like Tony is describing and in these I have seen
two types; one using the rectified output of a variac to control
the reactor and another that used a variable D.C. supply. Lastly I
have seen on the very newest bombarders a smallish solid state box
used to control the transformer. I never found a shop willing to
let me look inside the box to see what kind of circuit is being
used in these solid state units. I myself have known about
saturable reactors for many years now and have mentioned them on
this list several times over the past few years. I have built a
couple but not without a LOT of effort. I have yet to find a
"formula" to help with the design. It requires one heck of a lot of
trial and error. But for a couple of years now I have been
intrigued with the possibility of using an even less known circuit;
the gyrator that allows one to use a capacitor to appear to be an
inductor. This circuit is sometimes found in the more expensive
audio graphic equalizers, instead of inductors so they do not pick
up any hum. The problem with the gyrator is it uses an operational
amplifier to make the capacitor appear as an inductor and I have
yet to see the schematic for a discrete component op-amp, and since
op-amp chips are only available in the low wattage or fractional
wattage range at best they are useless in controlling a
multi-kilowatt transformer.
                               Alfred A. Skrocki
                 Visit my Do-It-Yourself Aquarium WEB page at:

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