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Best Primary Coil
Subject: Best Primary Coil
Date: Mon, 21 Apr 1997 13:49:29 -0700
From: Gary Weaver <gweaver-at-earthlink-dot-net>
To: tesla-at-pupman-dot-com
SEARCH FOR THE BEST PRIMARY COIL
For several months I have been building and testing primary coils.
Without going into a lot of details and turning this into a 5
meg file that will take you 2 hours to read I will list only what is
important. Each primary coil was tested using the same power
supply, capacitor, spark gap, secondary coil and toriod. Then all the
primary coils were tested again and only one thing in the
circuit was changes. Example, in the 2nd test each primary coil was
tested using secondary coil #1, then repeated using
secondary coil #2, then secondary coil #3 and so on. Then each primary
coil was tested a 3rd time using several different
spark gaps. Then each primary coil was tested a 4th time and only the
toriods were changed. Then each primary coil was
tested a 5th time and the power supply was changed. The goal is to find
out what works best and gives maximum secondary
coil spark output.
CIRCUIT. The spark gap is connected in parallel with the power supply.
The LC circuit is connected in parallel with the
spark gap. 1 safety gap is connected in parallel with the power
supply. 2 safety gaps are connected from each high voltage
terminal to ground. A choke coil is connected between each high voltage
terminal and the spark gap. The secondary coil has
a good earth gound.
SPARK GAPS I tested each coil using several different spark gaps. I
have found that the Richard Quick variable speed
vacuum fan quenches the spark gap the best.
Richard Quick spark gap. Copper tubes 1"x2". 8 gaps are .025 each.
Muffin fan cooled.
Richard Quick spark gap. Copper tubes 1"x2". 8 gaps are .030 each.
Muffin fan cooled.
Richard Quick spark gap. 10 tungston carbide gaps spaced .025 each.
Muffin fan cooled.
Richard Quick spark gap. Copper tubes 1"x2". 8 gaps are .025 each.
Vacuum fan cooled.
Richard Quick spark gap. Copper tubes 1"x2" water filled. 8 gaps are
.025 each. Muffin fan.
POWER SUPPLY I tested each primary coils with 1 neon then retested
them with 2 neons in parallel then retested them a
3rd time with 3 neons in parallel and so on. All neons are in phase and
voltage matched within a few volts.
12,000. volts 30 ma
12,000. volts 60 ma
12,000. volts 90 ma
15,000. volts 30 ma
15,000. volts 60 ma
15,000. volts 90 ma
15,000. volts 120 ma
15,000. volts 150 ma
18,000 volts 1 amp with current limiting.
CAPACITORS I tested each pirmary coil one at a time then added more
capacitance in the LC circuit and retested each
primary. Each capacitor is rolled .010 aluminum flashing and 18 layers
of .006 mil polyethylene. Each capacitor is vacuum
pumped and back filled with high voltage transformer oil. Each
capacitor was tested with a capacitor tester for the exact
value.
.01 uf rated 40,000. volts
.01 uf rated 40,000. volts
.0014 uf rated 40,000. volts
3/8" TUBING PRIMARY FLAT WOUND. The coils tested here are all made with
3/8" copper tubing. All coils are flat
wound. The only thing that changes in this test is the spacing between
turns. I made coils with .250, .375, .500 and .625
inches between turns. The inside diameter of all the coils are the
same. All coils have 16 turns. I tested each primary coil one
at a time and did not change any thing else in the circuit. Then I
retested the primary coils changing things one at a time. In
every test the tighter wound primary coil works the best. The .500
coils works better than the .625 coil. The .375 coil works
better than the .500 or the .625 coil. The .250 coil works better than
all the other coils. The tight wound coil is the best.
1/4" TUBING PRIMARY FLAT WOUND. The coils tested here are all made with
1/4" copper tubing. All coils are flat
wound. The only thing that changes in this test is the spacing between
turns. I made coils with .250, .375, .500 and .625
inches between turns. The inside diameter of all the coils are the
same. All coils have 16 turns. I tested each primary coil one
at a time and did not change any thing else in the circuit. Then I
retested the primary coils changing things one at a time. In
every test the tighter wound primary coil works the best. The .500
coils works better than the .625 coil. The .375 coil works
better than the .500 or the .625 coil. The .250 coil works better than
all the other coils. Again the tight wound coil is the best.
1/4" and 3/8" COPPER TUBING. In this test I compaired the best of the
best. The best 1/4" tubing primary is spaced .250
between turns. The best 3/8" tubing pirmary is spaced .250 between
turns. In all the tests I did the 1/4" copper tubing
primary out performed the 3/8" copper tubing primary coil. Center to
center each turn of the 1/4" tubing is .500" and the 3/8"
tubing is .625" center to center. The 1/4" copper tubing primary is
wound tighter than the 3/8" copper tubing primary. Again
the tight wound coil proves to be the best.
1/4" and 3/8" TUBING PRIMARY 30 DEGREE ANGLE. Now that I know the tight
wound primary coils work the best I
built and tested 2 coils helial wound on a 30 degree angle. One coil is
made with 1/4" copper tubing .250 between tubes. The
other primary is made with 3/8" copper tubing .250 between tubes. The
coil wound with the 1/4" copper tubing works better
than the one wound with the 3/8" tubing. Even though the 1/4" tubing
coil works the best the coupling difference here is not as
much as it was with the 2 flat wound primary coils.
1/4" TUBING PRIMARY FLAT, 15 AND 30 DEGREE ANGLE. Now that I know the
tight wound primary made with
1/4" copper tubing works the best I built and tested a coil helical
wound on a 15 degree angle. I compaired this coil to the
1/4" flat wound coil and the 1/4" 30 degree helical coil. The 15 degree
angle coil couples much better than the flat wound coil.
The 30 degree coil couples a little better than the 15 degree coil.
There is a very big coupling difference between the flat
primary and the 15 degree primary coil. In all my tests the secondary
coil output is much better using the 15 degree primary
compaired to the flat primary coil. When compairing the 15 deg coil to
the 30 degree coil the 30 degree coil coupling is a little
better but has some disadvantages. I am getting lots of strikes from
the toriod to the strike rail with the 30 degree primary.
With the 16" diameter toroid 21" above the strike rail the sparks prefer
to travel out and curve around and come back a!
nd hit the strike rail traveling
a distance of 34". Even with a 27" toroid on the 6.625" dia. x 23"
tall secondary coil the sparks from the 27" toroid go out
and curve around and come back and hit the strike rail of the 30 degree
coil. I am having a hard time getting any long sparks
from the toroid because they all want to strike the 30 degree primary
coil or the strike rail. Also the 30 degree primary is
causing me some over coupling problems but the 15 degree primary is on
the border line of over coupled. Raising the
secondary coil up several inches above the 30 degree primary coil solved
some of the problems. I made several atempts to
raise the toroid up several inches above the secondary coil to stop
arcing to the strike rail of the 30 degree coil but now the
arcs are coming from the top turn of the secondary coil not the toriod.
At 15K 150 ma I get only a few strikes to the 15
degree primary strike rail using a small aluminum foil covered toroid
but have gotten lots of strikes to the 30 degree pr!
imary coil and strike rail.!
I redu
ma and did not receive any strikes to the 15 degree primary or strike
rail but I am still getting a few strikes to the 30 degree
primary coil and the strike rail. With the power reduced to 15K or 12K
30 ma I got no strikes to the 30 degree primary coil
or strike rail. The 15 degree primary is giving me some very long
secondary coil sparks at any power setting I choose. The 15
degree primary coil does fine with any of the 4" or 6" secondary coils.
The 15 degree primary coil does fine with any toroid I
choose to use with the secondary coil. The 15 degree primary coil is
clearly the best choice within this power range.
STRIKE RAIL I made the strike rail using 1 turn of 1/4" copper
tubing. The strike rail is 2" above the primary coil and 1/2"
short of being a complete turn. The strike rail is connected to the
earth ground along with the bottom end of the secondary
coil. I was surprised to find that the strike rail some how increases
primary secondary coil coupling and after readjusting the
coupling the secondary coil spark discharge length has increased by 1".
With the 30 degree primary coil a strike rail must be
used to protect the neons from damage. I am getting lots of sparks from
the toroid to the strike rail and primary coil of the 30
degree primary. Even with the strike rail on the 30 degree primary I
lost 2 neon transformers. With the 15 degree primary coil
a strike rail is a much needed safety device. I received only a few
strikes from the toriod to the strike rail of the 15 degree
primary coil and no strikes to the primary coil. I did not receive any
strikes from the toroi!
d to the flat primary coil.
ARC OVER The bottom end of the secondary coil must be kept a safe
distance away from the inside turn of the primary coil
to prevent arc over. Arc over can short out your neons. I have lost 1
neon from arc over. Using a .01 uf capacitor in the LC
circuit and a 12,000. volt 30 ma neon, the primary coil secondary coil
spacing should be .500". apart between the inside turn
of the primary coil and the 1st turn of the secondary coil. Using 12K
60 ma the 2 coils should be 1.125" apart. Using 12K 90
ma the 2 coils should be 1.750" apart. If the LC circuit capacitor is
increased from .01 uf to .02 uf the spacing between the
coils should be increased by .250". If the 12K neons are increased to
15K the spacing between the 2 coils should be
increased by .125". These tests were done with a 27" toroid. If the
toroid diameter is reduced from 27" to 16" diameter then
the space between the 2 coils can be reduced by 1/8".
PRIMARY TURN TO TURN ARCING. In all the tests I did I never had any
problems with primary turn to turn arcs. With
the Tesla Coil maxed out to its peak and using the 15 degree primary
with 1/4" copper tubing spaced 1/4" between turns
tapped at turn 15.75, secondary coil 6.625" dia. x 23" long wound with
# 24 wire, 12K 90 ma power supply, .0214 uf
capacitor, 10" x 27" diameter toroid and a Richard Quick variable speed
vacuum spark gap with a total gap of .200, I got
only 1 turn to turn spark on the primary. 1 spark is not a problem as
far as I can see. It was not a spark that acred over and
over or a long time, it was just one spark that lasted a micro second
and was never seen again. This setup got me lots of 51"
long spark from the toroid. Maximum spark length so far is 66".
VACUUM FAN SPARK GAP. While doing these tests I discovered that the
Richard Quick varable speed vacuum fan
spark gap works the best. I am using a high speed vacuum fan that I
bought from American Sicence Surplus. It has an
AC/DC type motor. I am using a variac to adjust the RPM's of the fan. I
have found that as the fan RPM's increase the
secondary coil spark output also increases. There is a limit where the
tesla coil peaks out at a certain fan RPM. If the fan
RPM's are increased past this peak point the spark gap is over quenched
and the secondary coil output sparks get shorter.
The variac makes it possible for me to quench the gap to maximum
performance. When running the TC on 12K or 15K 30
ma I am using 4 of the 8 gaps. If I increase the power to 12K or 15K 60
ma I am using 6 of the 8 gaps, the primary
secondary coil coupling has to be adjusted and the vacuum fan RPM's has
to be increased. If I increase the power again to
12K or 15K 90 ma I am using all 8 of the !
gaps, the primary secondary coil
coupling has to be adjust again, and the vacuum fan RPM's has to be
increased again.
TOROIDS I tested several toroids. A 6" copper sphere, 5" x 12" dia.
stainless steel toroid, Basket Ball covered with
aluminum foil, 4.5" dia. x 16" dryer hose covered with aluminum foil,
10" galvinazed elbows 4 in a circle 27" diameter, and
NO toriod. The 10" thick x 27" diameter toroid gave me the longest
spark output of 66" with 3 neons in parallel. Using the
4.5" x 16" diameter aluminum foil covered toroid I get about 6 or 7
splitting streamers each about 32" to 37" long. With all the
other toroids I had no trouble getting several splitting streamer sparks
about 36" long. A large smooth surface toriod with a
bump gives me 1 very long discharge spark. A ruff surface toroid like a
dryer hose and basket ball covered with aluminum foil
gives me lots of long splitting streamers.
SAFETY GAPS & CHOKE COILS. With the Tesla Coil fully maxed to the limit
the safety gap and choke coils don't seem
to prevent neons damage. I have never lost a neon running a Tesla
Coil with just 1 neon transformer but when running 3
neons in parallel its just a matter of time and 1 or more neons will get
fried. From what I see here the number one cause of
neon damage is arc over and primary coil strikes from the toroid. I
have lost 7 neons so far.
SECONDARY COILS. I tested several secondary coils with all the primary
coils. All the coils are close wound on PVC
pipe and coated with polyurethane. The larger diameter coils require
more power input than the small diameter coils.
Operating the Tesla Coil on just 1 neon of 12K or 15K 30 ma coil #3
produces the longest and hottest sparks. When
operating the Tesla Coil with 3 neons in parallel coil #7 produced the
longest and hottest sparks. I am sure this can be
improved by winding a secondary coil with larger diameter wire.
#1.......3.5" dia. x 15" long #28 wire.
#2.......3.5" dia. x 15" long #24 wire.
#3.......4.5" dia. x 11.5" long #24 wire 266 turns 2 wires wound side by
side connected in parallel.
#4.......4.5" dia. x 11.5" long #24 wire 532 turns.
#5.......4.5" dia. x 13" long #24 wire.
#6.......4.5" dia. x 21" long #24 wire.
#7.......6.625" dia. x 23" long #24 wire 1064 turns.
#8.......6.875" dia. x 37" long #24 wire.
THE FINAL TEST. I am using the 15 degree helical wound primary coil,
secondary coil #7, .0214 uf capacitor, 10" x 27"
toroid, Richard Quick variable speed vacuum spark gap, 18,000. volt 1
amp transformer, and a current limiting transformer.
The primary secondary coil arc over space is 2". At 2000 and 3000 watts
there are no strikes from the toroid to the strike
rail, the vacuum spark gap is doing very well and I am getting very
thick white hot sparks from the toroid. At 4000 watts I am
getting very thick white hot sparks about 7' long from the toroid using
a #16 nail stuck to a magnet on the side of the toroid.
Some of the sparks go out from the toroid 3' curve around and come back
and hit the strike rail traveling a distance of 6'. I
moved the nail up higher over the radius of the toroid side so it points
up at an angle of about 15 degrees and now there are no
more arcs to the strike rail. At 4800 watts I am getting very thick
white hot 8' sparks from the nail. By mov!
ing the nail to different locati
on on the toroid I can direct the sparks at any thing I want. I removed
the nail from the toroid and now I am getting 100's of
random white hot thick sparks in all directions around the toroid to the
floor, walls, ceiling, strike rail, bicycles, lawn mover,
garden tiller, mini bike, work bench, light fixture, tool box, desk, air
compressor, garage door and everything in the room.
With the nail I can direct all the sparks in one direction but with out
the nail I have no control over the sparks. I have run the
TC several times at 4800 watts for 30 to 45 seconds each time with the
Richard Quick variable speed vacuum spark gap set
at about 3/4 full speed and it is doing very well, much better than I
expected. I will have to move the TC outside to try it on
10,000. watts. I got no primary secondary coil arc over and no primary
coil turn to turn arcing. All the discharge sparks are
very powerful and white hot.
CONCULSION. I can clearly see that a tight wound primary coil works
best. For the power range that I am experement
with the 15 degree helical wound primary is my 1st choice. 1/4" copper
tubing has proven to be better than 3/8" copper
tubing in these tests. The Richard Quick variable speed vacuum spark
gap out performed all the other spark gaps I tested and
performed well up to 4800 watts. A large smooth toroid with a bump
produces a long sparks and a ruff surface toroid or
smooth surface toroid with no bump produces lots of uncontrolable
sparks. The .02 uf capacitor produces longer and hotter
discharges sparks from the toroid than the .01 uf capacitor in the LC
circuit. Secondary coil #7 produces the longest and
hottest sparks from 1000 watts to 4800 watts. The 30 degree tight wound
primary coil is a fine choice for a 500 watt Tesla
Coil. The 15 degree tight wound primary is the best choice for a Tesla
Coil 1000 watts to 4800 watts.
DRAWING. I have attached a drawing to this post of the 15 degree
primary coil that I built.
SPECIALIST & GENERALIST. A specialist learns more and more about less
and less until he knows everything about
nothing. A generalist learns less and less about more and more until he
know nothing about everything.
Gary Weaver