Re: Current Limiting and Impedence

["Tesla list" <tesla@xxxxxxxxxx>]

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

Hi Paul,

I started out with a secondary 2" diameter and about 14" long.

I then purchased a second hand coil that is 14" diameter and about 56" long.

Thanks,

Paul.

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Thursday, May 12, 2005 3:09 AM
Subject: Re: Current Limiting and Impedence


> 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
>  > >
>  > >
>  >