[TCML] magnifier efficiency
futuret at aol.com
futuret at aol.com
Sun Dec 7 11:42:59 MST 2008
Many folks have expressed an interest in gaining a better
understanding of magnifier behavior and how it compares
to classic coil behavior. Here's a way to look
at the situation. In a magnifier there are 3 coils; the
primary, the secondary, and the extra coil or resonator.
When tuning a magnifier, the primary is tuned to the
combined inductance and capacitance of
both the secondary and the extra coil.
Often in a magnifier the extra coil inductance may be
3 to 7 times larger than the secondary inductance.
Let's say one wants to modify their magnifier by
reducing the inductance in the extra coil. If this is
done, and if one wants to keep the same primary
tune point, then the inductance in the secondary
will need to be increased to compensate for the
reduced inductance of the extra coil. This process
could be continued, gradually reducing the inductance
in the extra coil, and gradually increasing the inductance
in the secondary. Eventually a point would be reached
where only one turn is left in the extra coil. This could
actually be a tiny single turn maybe 1" in dia, and
1/4" in height. The bulk of the inductance and capacitance
would be in the secondary at this point. Some folks
have talked about the length of their sparks relative to
the extra coil. In the case of the tiny extra coil I
described above, the spark would be 480 times longer
than the extra coil if the spark is 10
feet long and
the extra coil is 1/4" in height. Obviously this is
not a good way to describe the "efficiency" of a magnifier.
One should take into account. the physical size
of both the extra coil *and* the secondary.
Going even further in this direction of reducing
extra coil inductance, one could eliminate the extra
coil completely. At this point all that would remain
of the extra coil would be a toroid mounted on a tall
insulated column. A transmission rod would connect
from the top of the secondary to the middle of the
toroid. This experiment has actually been performed
by a TCML member. He found that not much corona
emitted from the transmission rod. The sparks emitted
from the remote toroid set atop the insulated column.
This is exactly like a classic coil, but with a remote
toroid connected with a transmission line. The final
step in converting the magnifier to a classic coil is
to move the toroid from the column to the top of the
secondary, perhaps placing it on top of any existing
secondary toroid, then eliminating the transmission
line of course.
Regarding coupling in the system, the following should
be noted. Often it is said that a magnifier uses tight
coupling. This is not entirely accurate because although
the primary to secondary coupling is tight in a magnifier,
the overall coupling of the system is similar to that of
a classic coil. The presence of the extra coil actually
reduces the20overall coupling of the system. This effect
has been mathematically described by Antonio DeQueroz
on this list. There is probably more information about this
at his website:
Antonio also discusses other aspects of magnifier
behavior at his website including ways in which the
energy can be fully trapped in the extra coil. For this
to be realized, a faster quenching gap is needed. It's
likely that mechanical rotary gaps are not up to the task.
The newer solid state DRSSTC type coils may be
better able to benefit from magnifier topology because
of their electronic quenching. It remains to be seen
if the instabilities of spark loading and spark growth
will interfere with the attainment of theoretical benefits.
This is just an overview. There are other magnifier
issues which I didn't adress above.
From: Peter Terren <pterren at iinet.net.au>
To: Tesla Coil Mailing List <tesla at pupman.com>
Sent: Sun, 7 Dec 2008 10:40 am
Subject: Re: [TCML] magnifier efficiency, was : Hi power/ little coil??
This crops up every year or so.
I could put a 1 inch resonator and attach it to my TC and claim that 6
foot sparks come from a 1 inch coil.
When you add up primary and secondary heights, Richard Hulls coils
performed well but total secondary plus tertiary coil height vs spark
length was of little advantage to a well perfo
rming standard TC with a
3:1 spark length to secondary coil height ratio.
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