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 21:14:52 -0800 (PST)
From: J. Aaron Holmes <jaholmes@xxxxxxxxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: RE: SUCCESS with Saturable Reactor from MOT's (fwd)

Can you elaborate on this?  This is a very interesting
point...I'm thinking you refer to the same issue one
runs into when paralleling variacs (which I'll admit,
I've never quite grasped :))

Regards,
Aaron, N7OE

--- High Voltage list <hvlist@xxxxxxxxxx> wrote:

> 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
> 
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