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Re: Saturable Reactors as Ballast
Original poster: "Mike" <induction@xxxxxxxxxxx>
Hi Carl,
I already made reply to your post, however in support
of your information search on saturable reactor control, today at
work I located and copied 4 prints of working commercial versions
used in induction heaters.
I then scanned them when I got back here at the lab.
Please find 4 simple prints in one zip file, 4 megabytes.
Each file is a JPG format picture of a 8 X 11 paper.
Access path is :
www.hot-streamer.com/mike2004/reactor.zip
You will note that most can be wired 240 or 480, also note on a
couple prints, they use "Sa" and "Fa", "Sb" and "Fb" at the terminals
on the print. This format is also used on the DC winding markings. It
means Start A, Finish A, etc.
This lets you be certain that you are in phase when jumping them for
series and 480 or parallel for 240 regarding the two AC windings.
Also, the DC control winding is marked in this format for cases that
have 3 saturable reactors, the control windings each have references
of winding position Vs polarity.
Please note typical per reactor DC control voltages are ~ 25, with
three in series and each shunted with 100 Ohm resistor ~ 100 watt,
the control loop voltage is usually set to max out at ~ 90 volts and
4 or 5 amps. A bit more amps on the real big machines.
Next week or two, if I can cut loose from other stuff at work, I will
try and use the LRC meter to get you some L values on the AC windings
as well as the control windings.
Mike
----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Wednesday, December 21, 2005 5:05 PM
Subject: Saturable Reactors as Ballast
Original poster: "Carl Litton" <Carl_Litton@xxxxxxxxxx>
Does anyone on this list have any experience building saturable
reactors for ballasting purposes? I found some older notes in the
archive suggesting that a second winding on an iron core inductor
can be used to introduce a variable DC voltage that will give full
range control of the inductance as the core approaches saturation.
I have been able to demonstrate the effect on a small scale with a
simple step down transformer by putting the primary in series with a
120 VAC ciruit and connecting the the secondary to the rectified out
put of a Variac. A 2.7 Henry inductor was reduced to a little less
than 1 Henry with 140 VDC in the control winding, allowing a small
light bulb just enough current to give off some visible light
(measured current 0.188 Amp with no DC control and no light to 0.42
Amp with 140VDC control and visible soft glow from bulb).
However, all attempts to do this on any large (20 to 250 lbs.)
inductors controlling a 240 volt circuit in the 30 to 150 Amp range
have been not only fruitless but have almost instantly slagged the
25 Amp bridge rectifier connected to the control winding.
I need to understand what I am missing here. Any theory or
especially winding diagrams of working reactors would be greatly
appreciated. I did find one article that suggested 2 AC power
windings in series and in phase have to be used with 2 DC windings
in series and "out of phase" with each other in order to cancel the
effect of induced AC in the control winding. But here again, no
practical application, turns ratios, winding configurations, etc.
Any thoughts?
Thank you,
Carl Litton
Memphis HV Group