RE: SUCCESS with Saturable Reactor from MOT's (fwd)

["High Voltage list" <hvlist@xxxxxxxxxx>]

Original poster: Steven Roys <sroys@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Wed, 1 Mar 2006 07:25:42 +1300
From: G. Tyler <gtyler@xxxxxxxxxxxxxxx>
To: 'High Voltage list' <hvlist@xxxxxxxxxx>
Subject: RE: SUCCESS with Saturable Reactor from MOT's (fwd)

With this arrangement you get harmonic currents in the battery, should put a
choke in series.

-----Original Message-----
From: High Voltage list [mailto:hvlist@xxxxxxxxxx] 
Sent: Wednesday, 1 March 2006 3:30 a.m.
To: hvlist
Subject: Re: SUCCESS with Saturable Reactor from MOT's (fwd)

Original poster: Steven Roys <sroys@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Fri, 24 Feb 2006 07:17:48 +0100
From: Finn Hammer <f-h@xxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: SUCCESS with Saturable Reactor from MOT's (fwd)

Carl,

Congratulations, this may be the most important discovery in quite some 
time.

I may be wrong, but from the schematic, it would appear that you have 
the secondaries wired in parallel pairs of opposing series, as you describe.
However, since the primaries are wired in pairs of opposing parallel, it 
would appear to me, that the effect is canseled, and you would in fact 
get voltage on the secondaries/controll windings.
Therefore I suggest that the schematic does not faithfully record the 
setup as you describe.
Perhaps this is more what is intended?
http://home5.inet.tele.dk/f-hammer/satur.jpeg

However, a very clever idea. I have never seen anyone taking the 
controll winding out on 2 separate cores.

Cheers, Finn Hammer

High Voltage list wrote:

>Original poster: Steven Roys <sroys@xxxxxxxxxx>
>
>
>
>---------- Forwarded message ----------
>Date: Wed, 22 Feb 2006 08:55:34 -0600
>From: Carl Litton <Carl_Litton@xxxxxxxxxx>
>To: High Voltage list <hvlist@xxxxxxxxxx>
>Subject: SUCCESS with Saturable Reactor from MOT's
>
>The following is cross-posted between the 2 lists since we think it will be
germane in both arenas:
>
>
>In our research into different types of ballast to control current demand
on various projects, we found that it is often useful to be able to vary the
current independently of the voltage if a single power supply is to be used
for multiple projects with different V and I requirements. In the process,
we ran across the concept of the Saturable Core Reactor.  The idea is
simple.  Introduction of a small variable DC voltage into a separate winding
on an iron frame inductor will bring the core to saturation, opposing the
inductance of the power winding.  The closer to saturation the core becomes,
the lower the inductance of the reactor and the larger the current that is
allowed to flow.   We find this concept intriguing because it offers
infinitely variable control of large currents by way of a low power control
circuit.  We have conducted several experiments on this subject and will
publish a comprehensive article when all of the data is in.  However, our
most recent experimental configuration has given such remarkable results
that we find it worthy of being reported separately.  
>
>One of the major drawbacks to creating a saturable reactor from scratch is
the requirement that the control winding consist of 10-100 times the number
of turns as the power winding in order to permit control of the power
winding with low current DC.  If the power and control windings have the
same number of turns, then it will require 100 Amps in the control winding
to regulate 100 Amps in the power winding.  This is hardly efficient.  With
10 times the number of turns, control of 100 Amps would require only 10 Amps
DC and with 100 times the number of turns, only 1 Amp would be necessary.
The winding of several thousand turns on a transformer is daunting to say
the least.  We have therefore been looking into the use of transformers with
configurations that would require the least amount of modification.  In the
process, we have worked with several core types: round, EI, figure 8, etc.
A recent post to the HV list by Aaron Holmes suggested the possibility of
using two separate transformers.  Having a huge supply of MOT's many of
which are identical in brand and model number, we decided to test this
concept.  We are pleased to report a very successful result.
>
>Two pairs of MOT's were selected.  Each MOT was of the older stouter design
type, weighing around 15 lbs. and possessing heavy gauge primary windings.
For each pair, the primaries were wired together in parallel.  The
secondaries were placed in series by connecting the HV tab of each unit and
connecting a wire to the frame of each by means of a bolt run through one of
the mounting hotels in the frame.  These output wires were connected to the
HV side of a 125:1 NST to which a DMM was connected to the LV side.  0-145
VAC was introduced into the parallel MOT primaries while monitoring the DMM
for voltage.  If no voltage registered, the DMM was moved to the HV side of
the NST and the procedure was repeated.  A value of 30 Volts or less
indicated a successful series connection in the 'opposing' sense and
confirmed that the transformers chosen were close enough to identical to
proceed.  If the first test had indicated significant high voltage output,
one pair of wires in the parallel primary connection was swapped and the
test repeated to confirm that the seriesed secondaries no longer registered
significant voltage.
>
>Direct measurement of the inductance of the paralleled primaries was then
performed with an ammeter in series with the input supply circuit set at 35
VAC.  The ammeter registered about ? Amp, indicating a baseline inductive
reactance of around 60 Ohms.  The ends of the seriesed secondary circuit
were the wires attached to the frame of each transformer.  This series forms
the DC control winding. These wires were attached to the rectified output of
a small Variac.  The introduction of 0-82 VDC into the control caused the
reading on the ammeter to increase smoothly over the range to a final value
of 16.9 Amps.  We did not push this further due to the 20 Amp limitation of
the ammeter, but this corresponds to an inductive reactance of slightly over
2 Ohms, making the test a resounding success.  With cooling, this pair could
reasonably be expected to handle 40 or 50 Amps as ballast and the other pair
gave a very similar test result.
>
>The question then became whether the two pairs could be successfully
paralleled for higher current handling capability.  To this end, shunt wires
were run to connect two sets of paralleled primaries.  Then, the two sets of
seriesed secondaries were connected in parallel with respect to each other.
A brief power test was performed just to insure that no voltage was induced
into the control.  At this point, the inductance/saturation testing was
repeated on the combination of all 4 MOTS.   The testing was also very
successful and the results very similar to those from the tests of the
individual pairs with a couple of exceptions, which are as follows.  First,
the baseline reactance was reduced to about ? of the value measured on the
individual pairs - 30 Ohms instead of 60.  This was to be expected pursuant
to the law of parallel inductors.  Second and more surprising, there was
only required a total of 28 VDC in the control to reduce this value to 2
Ohms.  It would seem to follow that more pairs could be added with a
corresponding increase in current capability and decrease in baseline
reactance.  The high end reactance drop should not resent a problem since
the useful range of inductive reactance for most of our project work is
about 2-8 Ohms.
>
>An admittedly poor but serviceable photo of the 4-MOT reactor stack has
been placed here:
>
>http://hvgroup.dawntreader.net/srmots.jpg
>
>The schematic is here:
>
>http://hvgroup.dawntreader.net/4motreactor.jpg
>
>
>
>We'd love to repeat this experiment with a pair of identical transformers
removed from 5 or 10 kVA pole pigs, but alas, they are not a plentiful as
MOT's around here.  
>
>
>Questions/comments are welcome.
>
>
>Carl Litton
>Memphis HV Group
>
>
>
>
>
>  
>