This design will look familiar after we think back to our science fair days when we dimmed a light bulb with a coil of wire and a steel rod. It worked then, and since it ain't broke, I won't fix it, and I'll draft it for service here at AAA Welder. The operation is simple. When the control rod is fully retracted, the only effect on the circuit is that of an air core inductor. When the control rod is fully inserted, the coils' "reactance" is maximized.
My goal in building this reactor was to exact control over a small range of power, a few amps to fine tune my welder and to stabilize
the arc. If too many turns are put on initially, the high end amperage will be reduced significantly before the rod is even inserted.
The method I used to determine the amount of reactance I needed was to wind turns on the coil former, with the control rod fully inserted,
until the minimum amount of rod burning amperage was determined. From there, it was a simple matter to retract the control rod until I had
the exact amperage I wanted. I then locked the rod in place with the ring clamp.
I know, this is not very scientific when it comes to determining the Henries of a very large inductor however, it is a fast, effective
means to an end and it works. For the curious and those that want to know the technical workings of an inductor
Understanding the principles of an inductor definately gave me the advantage when it came to designing this inductor for my welder. I highly recommend a basic knowledge of charged wire coils.
Gathering the parts for this build was easy. Except for a solid steel rod, I found everything I needed in my garage left over from other projects I've built.
In leiu of a steel rod, I cut 5 inches of 13/16" O.D. tube steel from an old broom handle, filled that with Iron powder and sealed the tube with a wooden plug on one end and a hot glue plug in the other. The coil was formed on a 3 inch piece of 1" PVC pipe that measured 15/16" I.D.. The windings were stabilized with hot glue as they were wrapped to keep them in place.
The final step for finishing the PVC coil former is to take a hacksaw and cut 4 slots on the Cardinal points, N-S-E-W, so that when the ring clamp is installed on the PVC, the PVC will compress onto the steel tube and lock it in place.
This design may not posess futuristic complexity but, it works perfectly. With no moving parts to wear out, it should serve faithfully and indefinately.