RE: Current Limiting and Impedence

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Mark Dunn" <mdunn@xxxxxxxxxxxx>


Paul(Benham):

Are you using the MOT's for HV Transformers or Inductors?

Thanks.
Mark


Original poster: "Paul Benham" <paulb@xxxxxxxxxxxxxxxxxxxx>

Hi Mark,

Cutting off the I's on MOT's and bolting them back together with plastic
spacers is exactly what I do.  I have run 4 in series on a 2" coil and
on my 14" coil I have two in series and another two in parallel.

After extended running one of the MOT's insulation broke down, but I do
have up to 10kV across each of the two MOT's so they are being pushed
quite hard. I need to go to three in series and more in parallel.  It is
becoming a bit of a joke, carting around so many MOT's but they came at
the right price and do work.

Cheers,

Paul.

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Tuesday, May 10, 2005 5:44 PM
Subject: Re: Current Limiting and Impedence


 > Original poster: "Mark Dunn" <mdunn@xxxxxxxxxxxx>
 >
 >
 > Steve, Gerry, Jim, Paul, et all:
 >
 > When I started this thread it was to discuss issues with current  >
limiting and has now progressed into Charging Reactor Design.  That's  >
OK, but we need to keep straight what we are talking about.  >  > Right
now I am returning to the original current limiter issue and will  >
come back to Jim's charging reactor in later post.  >  > As you know, my
current limiter was saturating.  It was very interesting  > to follow
the discussion between Gerry and Steve, because what they  > discussed
was exactly what I was running into.  I needed many turns to  > get the
B(Core Flux Density) low enough, but the high turns drove the  >
inductance through the roof and demanded a huge gap to get it back down.
>  > Last week I began analyzing a "bad" MOT(coincidently a destroyed  >
charging reactor)  I have to see if I could use it for a current  >
limiter.  A similar "good" MOT had a primary inductance of ~300 mH(sec
> open).  I measured Ve & Ae and calculated Le & C.  Then back figured
> ~AL.  Preliminary analysis suggested B would be around 500 mT which  >
should be OK for steel.  >  > I cut the "bad" MOT unit apart and was
surprised to find that all the
 > E-core laminations were in the same section.   All the I-core
 > laminations were in the other section.  This meant I could easily gap
> this device.  (Note: I sawed it apart right at the weld on either
side.  > I ran a weld bead parallel, and above and below, each original
weld so  > that the laminations would not fall apart before I sawed
through it.)  >  > I made a 60 turn coil(R=0.2 Ohms) and placed it on
the E-core, clamped  > the I-core on top, measured V,I and computed Z &
L with no gap.  L = 38  > mH.  This gave me an AL = 10555 nH.  Does this
make sense for steel?  > I then measured L for a number of gap spacers
up to about .070"(note  > this means total gap of .140") when I reached
~4 mH.  My theoretical  > math suggests that I should be around .070"
total gap or .035" spacers.  > Are gapping calculations highly accurate
or do they just give an  > approximation?  B will be around 620 mT which
is good for steel.  > (Another data point of interest was .009" spacer
for .018" total gap and  > L = ~15 mH.  This would meet the criteria of
my original current  > limiting requirements.)  >  > Pls comment about
this design.  Like to delve into the math issues with  > you guys if
your willing to work with me.  I think my issues are in the  > Ui, Ue,
Ur area.  >  > Thanks.  > Mark  >  > Mark  >  >