Re: Current Limiting and Impedence

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Paul B. Brodie" <pbbrodie@xxxxxxxxxxxxx>

Paul,
Is that 2" coil a typo or do you really have a little TC?
Paul
Think Positive

----- Original Message -----
From: "Tesla list" <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx>
To: <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx>
Sent: Wednesday, May 11, 2005 1:50 PM
Subject: Re: Current Limiting and Impedence

> Original poster: "Paul Benham" 
<<mailto:paulb@xxxxxxxxxxxxxxxxxxxx>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" <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx>
> To: <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx>
> Sent: Tuesday, May 10, 2005 5:44 PM
> Subject: Re: Current Limiting and Impedence
>
>
> > Original poster: "Mark Dunn" 
<<mailto:mdunn@xxxxxxxxxxxx>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
> >
> >
>
>