Saturable Reactors

To: tesla-at-poodle.pupman-dot-com
Subject: Saturable Reactors
From: Tesla List <tesla-at-stic-dot-net>
Date: Fri, 02 May 1997 23:42:57 -0500
Approved: tesla-at-stic-dot-net
Subject:   Saturable Reactors
  Date:    Thu, 1 May 1997 23:54:44 +0500
  From:    "Alfred A. Skrocki" <alfred.skrocki-at-cybernetworking-dot-com>
    To:    tesla-at-pupman-dot-com


On Tue, 29 Apr 1997 07:47:10 -0400 Steve Falco
<sfalco-at-worldnet.att-dot-net> wrote;

> > This is why I use a home built saturable reactor to control
> > the input power on my larger coils
> 
> This is very interesting to me.  Would you please consider posting a
> description or some construction info to the list?  I'd like to try
> building a saturable reactor myself...

Ok Steve, first I want to apologize for not responding sooner but I 
have been having trouble with my e-mail which hopefully now has 
been corrected.

Now a little background on saturable reactors. A saturable reactor is 
essentially a transformer with a third winding that is feed D.C. as 
more D.C is feed into this third winding the core becomes gradually 
more and more magnetized and less and less responsive to the A.C 
passing from the primary to the secondary consequently as more D.C. 
is applied to the third winding the A.C coming from the secondary as 
well as the current pulled by the primary decreases until the D.C has 
saturated the core and no current will be drawn by the primary nor 
will there be any secondary output. Saturable reactors were rather 
popular in use until the end of the 1950's when solid state 
technology started to replace almost everything. Saturable reactors 
were also sometimes called magnetic amplifiers due to the fact that 
they can be designed such that a comparatively small D.C. current can 
control a comparatively large A.C. current flowing through the 
primary and secondary. This can be achieved by using many turns of 
comparatively small gauge wire, the more turns for a given voltage 
the faster the core saturates or another way of looking at it is the 
greater the number of turns the smaller the D.C. voltage needed to 
control the core. I have found great difficulty finding books with 
design information since these references are now long out of print. 
If you have access or occasionally find old (pre- 1960's) electrical 
and electronic engineering handbooks you may luck out and find some 
good design info, if so please post the info to the list! What I have 
done with relatively good success is to find a transformer core of 
the wattage I want to control (preferably with the primary intact) I 
then wind a secondary identical to the primary thus making an 
isolation transformer. Next I impericaly find the appropriate 
windings for the D.C. control by winding on a pound or so of 
typically #28 B&S gauge enamel coated wire, I then apply a variable 
D.C to this winding while running an appropriate load on the 
isolation transformer and measure input and output voltages and 
currents if I don't have enough control over the core I add more wire 
if I find the core saturation too sensitive I remove some turns until 
I am happy with the control. Lately I have been experimenting with an 
altered design to save on the copper. What I am experimenting with 
presently is to use the same core but only one A.C. winding and the 
D.C. control winding thus making it truly an adjustable choke to be 
put in series with whatever load is to be controlled and the A.C 
line.

                               Sincerely

                                \\\|///
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                           Alfred A. Skrocki
                   alfred.skrocki-at-cybernetworking-dot-com
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