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

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

Original poster: Steven Roys <sroys@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Fri, 3 Mar 2006 18:06:44 +1300
From: G. Tyler <gtyler@xxxxxxxxxxxxxxx>
To: 'High Voltage list' <hvlist@xxxxxxxxxx>
Subject: RE: SUCCESS with Saturable Reactor from MOT's (fwd)

I detect a fellow ex telecom tech guy! Remember the windings have to
magnetise the iron, if the are together their fields just cancel and there
is no magnetisation.

-----Original Message-----
From: High Voltage list [mailto:hvlist@xxxxxxxxxx] 
Sent: Friday, 3 March 2006 4:33 a.m.
To: hvlist
Subject: Re: SUCCESS with Saturable Reactor from MOT's (fwd)

Original poster: Steven Roys <sroys@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Wed, 1 Mar 2006 20:40:05 -0800 (PST)
From: J. Aaron Holmes <jaholmes@xxxxxxxxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: SUCCESS with Saturable Reactor from MOT's (fwd)

You don't notice a difference because Finn's suggested
correction was made by the time hvlist woke back up :)

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

> Original poster: Steven Roys <sroys@xxxxxxxxxx>
> 
> 
> 
> ---------- Forwarded message ----------
> Date: Wed, 1 Mar 2006 16:47:56 +1300
> From: m.j.watts@xxxxxxxxxxxx
> To: High Voltage list <hvlist@xxxxxxxxxx>
> Subject: Re: SUCCESS with Saturable Reactor from
> MOT's (fwd)
> 
> I have to admit I'm struggling to see the difference
> between the two 
> circuits. As long as each pair of transformers have
> the control 
> windings oppositely phased it should work shouldn't
> it? A nice idea 
> indeed. Reminds me of hybrid telephony circuits in a
> way.
> 
> Malcolm
> 
> On 28 Feb 2006, at 7:30, High Voltage list wrote:
> 
> > 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, w
> e found that it is often useful to be able to vary
> the current independently of the voltage if a si
> ngle power supply is to be used for multiple
> projects with different V and I requirements. In the
> p
> rocess, 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 co
> re 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 experime
> ntal configuration has given such remarkable results
> that we find it worthy of being reported separ
> ately.  
> > >
> > >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 pe
> rmit 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 Am
> ps would require only 10 Amps DC and with 100 times
> the number of turns, only 1 Amp would be necess
> ary.  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 lea
> st amount of modification.  In the process, we have
> worked with several core types: round, EI, figu
> re 8, etc.  A recent post to the HV list by Aaron
> Holmes suggested the possibility of using two sep
> arate transformers.  Having a huge supply of MOT's
> many of which are identical in brand and model n
> umber, 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 aroun
> d 15 lbs. and possessing heavy gauge primary
> windings.  For each pair, the primaries were wired
> tog
> ether 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 i
> n the frame.  These output wires were connected to
> the HV side of a 125:1 NST to which a DMM was co
> nnected 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 t
> he 'opposing' sense and confirmed that the
> transformers chosen were close enough to identical
> to pr
> oceed.  If the first test had indicated significant
> high voltage output, one pair of wires in the p
> arallel primary connection was swapped and the test
> repeated to confirm that the seriesed secondari
> es no longer registered significant voltage.
> > >
> > >Direct measurement of the inductance of the
> paralleled primaries was then performed with an amme
> ter in series with the input supply circuit set at
> 35 VAC.  The ammeter registered about ? Amp, ind
> icating a baseline inductive reactance of around 60
> Ohms.  The ends of the seriesed secondary circu
> it were the wires attached to the frame of each
> transformer.  This series forms the DC control wind
> ing. 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 fi
> nal 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 resoundin
> g 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 curre
> nt handling capability.  To this end, shunt wires
> were run to connect two sets of paralleled primar
> ies.  Then, the two sets of seriesed secondaries
> were connected in parallel with respect to each ot
> her.  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
> i
> ndividual pairs with a couple of exceptions, which
> are as follows.  First, the baseline reactance w
> as 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 wa
> s 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
> decre
> 
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