[TCML] Ballastwith adjustable Core

[Jeremy Scott <supertux1@xxxxxxxxx>]

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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