[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Current Limiting and Impedence



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 > >