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Re: [TCML] magnifier efficiency
But, the formula most likely assumes 100% efficency and power transfer.
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Thanks,
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Shouldn't BeUsingMyName
Email: hsheltonj@xxxxxxxxx
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From: "futuret@xxxxxxx" <futuret@xxxxxxx>
To: tesla@xxxxxxxxxx
Sent: Monday, December 8, 2008 3:16:01 PM
Subject: Re: [TCML] magnifier efficiency
Hi David,
I see what you're saying. Putting the figures for Ed's coil into
my formula gives the following predicted spark length:
spark length (inches ) = 1.7*sqrt input power (watts)
45 amps x 240 volts = 10800 volt-amps
1.7*sqrt 10800 = 176" = 15 feet
So my formula "predicts" 15 foot sparks for Ed's
coil and he's getting 14 foot sparks. Probably if
he had more room he'd get 15 foot sparks.
Richard Hull's Nemesis coil also used about 11kW of
power and gave 15 foot sparks.
I don't know why your coil is drawing double the
power for the same spark length. I think your
12.5" dia x 49" secondary with 19awg wire should
be OK. I think the cause may be something else.
Certain types of ballasting can burn power. It's
possible your power factor may be poor, and may
be making the coil *appear* to be drawing more
power than it's really drawing. You'd need a true
wattmeter to be sure, or a power factor meter.
Richard's Nemesis coil had a 0.1uF cap also, and he
ran around 400 bps or so I guess. Of course
Richard had a huge 14" x 60" toroid. Richard used
a 10kVA, 10kV pole pig to power his coil. His
secondary was 14" dia, but I don't think it makes
much difference if a secondary is 14" dia vs. 12.5" dia.
If you run your coil outdoors, that may require extra
power also to make up for wind and air currents
John
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-----Original Message-----
From: David Rieben <drieben@xxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Sun, 7 Dec 2008 5:47 pm
Subject: Re: [TCML] magnifier efficiency
Hi John,
I have zero personal experience with maginifiers, so I am in
no way qualified to comment on them. However, aside from
the physical size of the secondary and/or tertiary coil, the one thing that I did notice when observing Ed Wingate's magnifier in action at his Teslathon last August was that his seemed to be very efficient in regards to total system input kVAs versus the total output spark length, and notably better than that of my Green Monster "classic" coil, I might add. Ed was getting solid 14 ft.+ arcs pretty consistantly while only pulling 45 to 50 amps from the wall plug. Of
course, I'm not telling you anything that you don't already
know, as you were there, too. ;^) I can barely get that type of performance with my Green Monster coil and only at the expense of about twice the wall plug amps. I too doubt
that it's just because Ed's is a maggie and mine is a classic coil but I do know what I saw. I suppose his huge "second-
ary" driver coil plus his 14" diameter extra coil made for a considerably larger total inductance than that of my 12.5" outer diamter x 49" long secondary coil, close wound with #19 magnet wire, on my Green Monster coil. I believe our to
roid toploads are fairly similar in size so I'm not thinking that the toploads would be a real issue in this comparison. Amazingly, Ed is only using .05 uFd of primary C too and my Green Monster is using .1 uFD but I believe Ed is run-
ning a higher BPS than I am, too.
David Rieben
----- Original Message ----- From: <futuret@xxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Sunday, December 07, 2008 12:42 PM
Subject: Re: [TCML] magnifier efficiency
All, (re-post)
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, graduall
y 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 c
lassic 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:
http://www.coe.ufrj.br/~acmq/tesla/magnifier.html ;
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.
Cheers,
John
-----Original Message-----
From: Peter Terren <pterren@xxxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
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. Peter www.tesladownunder.com
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