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Re: [TCML] magnifier efficiency
Hi David,
I did the original calculations for Kevin's Biggg Coil. I calculated
that
120 BPS was needed for that coil for the cap value he used.
If you do the calcs, you'll see it all works out. The LTR concept
doesn't apply to pig powered coils in the same was as to NST
coils. With pig power, the determination of LTR, resonant, or
STR depends on the setting of the ballast.
Actually I was very curious regarding how much power Kevin's
coil would actually draw, but it turned out he was using a very
lossy ballast, so a lot of power was lost in the ballast.
I'm not sure how much the build-up of ions in a room helps
the spark length. I'm not saying it doesn't help, but I don't
know of any scientific tests regarding that issue. But yes
the air currents and winds outdoors make a difference.
John
-----Original Message-----
From: David Rieben <drieben@xxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Tue, 9 Dec 2008 9:12 am
Subject: Re: [TCML] magnifier efficiency
Hi John,
You do bring up something that I had passively considered
in the past about my coil. I am forced to run it outdoors and
there usually is always at least a bit of wind currents. Obvious-
ly, wind currents are very slight indoors. Depending on the volume of
the indoor space in which the coil is operated,
the air can also begin to accumulate ions, which can make for20a
possibly lower breakdown voltage of the air, too. Kevin El-
drege in Oklahoma, is also forced to run his massive Biggg Coil
outdoors, too, though, and his coil gives incredibly long arcs (25
ft.+). Of course, he also has a huge 24" x 10 ft. long secondary coil
and an equally huge topload. I think he is also running it with an
SRSG, but is obviously not LTR with a total primary C of about .18 uFd,
if I'm not mistaken.
And - let's not forget that Kevin has PLENTY of raw power at his
disposal, too - something on the order of 55 kVA, but I still wonder
how he processes that much power if he is limiting his bps rate to a
synchronous 120 or even 240 bps
when his primary C is "only" .18 uFd ? Maybe Kevin could further
clarify if he is reading this :^)
David
----- Original Message ----- From: <futuret@xxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Monday, December 08, 2008 5:16 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 f
oot 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
--
-----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,=2
0so 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=2
0is 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 that206 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
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