Re: [TCML] Ballastwith adjustable Core

["DC Cox" <resonance@xxxxxxxxxxxx>]

At this power level you might suceed with a PT type coil.  For pole xmfrs
operation laminated cores are required to reduce, as you suspected, eddy
currents that can produce a lot of local heat.

Dr. Resonance




On Wed, Jun 25, 2008 at 12:01 AM, Jeremy Scott <supertux1@xxxxxxxxx> wrote:

> I've got an idea in mind for a ballast for my PT based coil that should
> limit the current to 30 amps and be adjustable (3.5KVA) The best part is
> I only have to buy one part.
>
> It's basically a spool (500ft) of that 12 gauge solid core 'Home Depot'
> copper wire (.122 wire diameter) wound 5 layers on the form of a 12"
> long by 3.5" diameter PVC pipe. I measured my spool and it's about 1.2
> ohms.
>
> Calculations put this around 9554uH or so, 31 -ish amps. Perfect.
>
> Now the fun part. This PVC pipe form has an inner diameter of 3 inches.
> McMaster Carr sells a 3" x 12" solid iron slug. My idea is to shove this
> thing in and out to control the current. Start up the coil with it fully
> inserted and then pull it out slowly.
>
> First thing, yeah, it's not laminated. Will eddy currents be a problem?
>
> Second thing, assuming the above works, would the changes in inductance be
> linear as I slide the coil in and out? Is there a formula I can use for
> inductors with slugs? It's kind of not worth it if the coil goes from half
> power to full blast with an inch of slug movement.
>
>
>
>
>
>
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