Re: adjustable inductors

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "S&JY" <youngsters@xxxxxxxxxxxxxxx>

Jim,

I made an adjustable inductor, to put in series with a TC primary, thusly:
I made two pancake coils out of #10 insulated solid wire.  One of the
pancake coils was mounted so it could slide toward and away from the other
on a common virtual axis.  The sliding coil was moved via a cheap electric
screwdriver turning a threaded rod, with limit switches to stop the coil
movement.  Coils can be wired either series-aiding or series-opposing.  No
brushes - just flexible connecting wires.  It worked OK, but I have
abandoned it's use and no longer have dimensions or measurement data.  An
alternate method is the same two pancake coils, but one of them mounts on a
hinge so it can swing away from the other coil.
--Steve Y.

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Wednesday, January 11, 2006 7:56 AM
Subject: adjustable inductors


> Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>
>
> Looking for ideas on adjustable inductors for a primary.. The idea
> being that you have a turn or two tightly coupled to the secondary,
> and the rest of the primary L is in an adjustable L.
>
> There's rafts of roller inductors around with suitable values, but I
> don't know that they'll handle the voltage, and the losses might be too
high.
>
> So, here's some ideas as grist for speculation:
>
> 1) Two nested coils, one on a positioner.  As you slide one in or
> out, the mutual coupling changes, changing the overall L of the
> pair.  A modified version has 3 coils, one moving, and two wound with
> opposite sense. The two are stacked end to end, so the position of
> the moving coil determines the effective L.  (think LVDT)
>
> 2) A coil within a coil, with the moving coil rotating (a goniometer).
>
> Both of these require brushes or flexible leads, I think
>
> 3) A coil with a permeable core that is moved in and out.
>
>
>
>
>