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Re: current limiting choke



In a message dated 96-06-07 01:10:53 EDT, you write:

>
>Hello all,
>
>I'm currently designing a current limiting choke to use with my pole pig.. 
>I have all things ready for construction but I'd prefer to have a reality
>check :) before making the big, heavy and expensive choke.. That thing
>will weight about 50kg when ready..
>
>The basic goal is to be able to both use very low powers (1kW) and higher
>powers (10kW) with the same basic choke. The easiest way to this seems to
>use a large iron I-core (10*16*30 cm, permeability 13) and wind several
>layers of coil to the form so that each layer is separate.  For maximum
>current all layers are connected in parallel and for minimum current all
>layers are in series.. I have a 20kg roll of 1.5mm dia magnet wire and
>this would mean about 200 ideal or 170 real turns per layer and something
>like 17mH for one layer (or all in parallel) and approximately 17mH*n^2
>for n layers in series. Those inductances with 120 ohms in parallel with
>choke would give about 4-50 amps area to choose current with several
>different combinations for different currents.
>
>Is there something I am missing in the design?
>
>Should I consider the primary capasitor (25nF) as "seen" through the
>pole-pig (about 180uF) or is this necessary - it would require more
>inductance to the choke to compensate.. 
>
>Thanks a lot for any comments,
>
>  Kristian.

Kristian,

Scott Myers and Glenn Cerny and I discussed this several months ago.  We came
up with a figure of 5 to 25 mh as a design goal for a variable inductor.  Let
us know how your project comes out.

Ed Sonderman