Re: Regulating coil: here's a big one!

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Scott Hanson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <huil888-at-surfside-dot-net>


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, May 27, 2002 12:25 PM
Subject: RE: Regulating coil: here's a big one!


> Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Gary.Lau-at-hp-dot-com>
>
> Let's please call these "tuning coils" - nothing is being regulated.
>
> Now here's the good news.  No power or performance is being wasted.  While
> the magnetic field from the tuning coil is not likely being coupled to the
> secondary, it is not going to waste.  Only if there is resistance, will
> there be heat generated and hence wasted energy.  The off-axis inductance
> of the tuning coil will merely somewhat reduce the pri-sec coupling, and
> the secondary can be moved closer to the primary to compensate.
 (SNIP)

I was merely using Tesla's descriptor for a "tuning inductor".  At the turn
of the century, "regulator" had a slightly different meaning than we now
use. For instance, in Tesla's day to "regulate" a mechanical watch meant to
adjust the escapement and mainspring preload to achieve best performance
(most accurate timekeeping).

As far as power being "wasted", the particular variable inductor I was
referring to has numerous metallic parts in its frame, etc. that assuredly
will have eddy currents induced in them, resulting in resistive heating and
some minor power loss. The sliding connections to the coil will also have
some resistive losses, minimized if the surfaces are kept bright and oxide
free.

Scott


>
>  -----Original Message-----
> From: Tesla list [mailto:tesla-at-pupman-dot-com]
> Sent: Monday, May 27, 2002 9:53 AM
> To: tesla-at-pupman-dot-com
> Subject: Regulating coil: here's a big one!
>
> Original poster: "Scott Hanson by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <huil888-at-surfside-dot-net>
>
> In an attempt to help put an end to the "variable capacitance" debacle, I
> thought I'd add a bit to the "regulating coil" thread.
>
> Saturday I picked up the largest variable inductor I've ever seen at the
TRW
> electronics swap meet in So Cal. Unlike the commonly seen ex-military
roller
> inductors, this one is "really big", and utilizes utilizes a pair of solid
> copper "shoes" on a slider to make contact with the windings. The windings
are
> rectangular section solid copper, .185" thick X .325" wide. The coil is 6"
long
> X 6.5" in diameter, with 14 turns total. As measured using a Sencore
Z-meter
> II, the range of inductance adjustment is from .1uH to 20uH. Weight is
just
> under 20 lbs.
>
> Some photos of this inductor can be seen via the following links. The
files are
> 150 - 200 kb in size, so they may take a little time to load.
>
<http://surfboard.surfside-dot-net/huil888/variableinductor1.jpg>http://surfboa
> rd.surfside-dot-net/huil888/variableinductor1.jpg
> http://surfboard.surfside-dot-net/huil888/slider.jpg
>
<http://surfboard.surfside-dot-net/huil888/coronaburn.jpg>http://surfboard.surf
> side-dot-net/huil888/coronaburn.jpg
> http://surfboard.surfside-dot-net/huil888/variableinductor2.jpg
>
> Technically, using a regulating coil "wastes" some of the energy in the
primary
> circuit as its magnetic field is not coupled into the secondary. However,
this
> loss might be offset by the ability to fine-tune the primary circuit's
resonant
> frequency as the coil is actually operating.
>
> The photos show several views of this massive inductor. An interesting
feature
> is shown in the photo labeled "corona burn". Clearly visible burned into
one of
> the insulating end plates is a flame-like defect originating at a sharp
corner
> of the square slider-shaft. The distance from this corner to the brush
plate
> (opposite terminal of the coil) is slightly over 2". It appears that this
coil
> was operated for some extended period of time with considerable corona
> originating from this point.
>
> As soon as I can rig up a gear motor to allow this to be adjusted from a
> distance, I'll add it to my 6" X 32", 120ma NST-powered coil and see if
dynamic
> tuning is worth the effort.
>
> Scott
>
>