"John Ferrell" wrote in message
...
On Thu, 19 Apr 2007 12:00:34 -0400, "Oppie"
wrote:

Anybody remember the name of the ancient dimmer that used a variable
inductor in series with the lighting circuit?

The chorus that I sing with is performing in a turn of the last century
theatre. I was marvelling at the ancient stage technology. They still have
the old style sandbag counterweights and belaying pins to anchor the lines
though the lines themselves have been changed from the original hemp lines
(guess they were all smoked by now...) to new black cotton lines that
conform to newer codes. The original lighting panel has long since been
replaced by a new digital board but I was talking with the theatre manager
and trying to remember some of the old names.

Rheostats, the original dimmer technology were replaced by the variable
inductor types to some extent. All of these were eventually replaced by
Variac types for many years until the newer electronic dimmers took hold.
I have fond memories of high school stage crew, running the Variac dimmer
board. On scene changes, the dimmers could be mechanically ganged into a
master group and master groups could be ganged to the grand master.
Sometimes it took two people to pull the grand master - and it had a 4
foot
handle. Oh, to have had a DMX back then.

Oppie
www.chordsmen.org


As I recall, the saturable reactor was a transformer with two
windings. One of the windings was in series with the input power to
the lights. The other winding was provided with a variable DC power.
When there was no DC present, the other winding was high impedance to
the lamp loads. When the DC was applied the core in the transformer
was saturated and the impedance went down as the lights came up!

John Ferrell W8CCW
"Life is easier if you learn to
plow around the stumps"
t

Saturable reactors used to be very common in TV E/W correction circuits, I
even recall a Relisys monitor that used one as a B+ regulator.