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Re: Current Limiting and Impedence



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

Mark,
Please excuse my ignorance. Will you please define the following:
Ve & Ae,
Le & C (capacitance?),
AL,
10555 nH (nano henries?),
mT (miliTesla's?),
and finally, Ui, Ue, and Ur.
I want to make sure I'm on the same page with you. I really appreciate what you are doing and your sharing it with me. You have been way more than helpful. Regards.
Paul
Think Positive


----- Original Message -----
From: "Tesla list" <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx>
To: <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx>
Sent: Tuesday, May 10, 2005 12:44 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
>
>
>