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Re: Figure this out.
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> From: Tesla List <tesla-at-poodle.pupman-dot-com>
> To: Tesla-list-subscribers-at-poodle.pupman-dot-com
> Subject: Figure this out.
> Date: Tuesday, January 21, 1997 12:25 AM
>
> Subscriber: gweaver-at-earthlink-dot-net Mon Jan 20 22:03:01 1997
> Date: Mon, 20 Jan 1997 10:41:06 -0800
> From: Gary Weaver <gweaver-at-earthlink-dot-net>
> To: tesla-at-pupman-dot-com
> Subject: Figure this out.
>
> Figure this out.
>
> [ Part 2: "Attached Text" ]
>
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>
> Can someone explain this. I have 3 neons in parallel. The power supply
is 15KV 90 ma. The maximum spark length at the secondary is 44". I added
another neon making the power supply 15K 120 ma. The maximum spark length
at the secondary is still 44". I added another neon making the power
supply 15K 150 ma. Now the maximum spark length dropped to 39". With
more power the output gets smaller?
*** Sounds to me like there is an imbalance among the transformers. If one
is producing 15KV, for example, and another is producing 14.9KV, then when
they are Paralleled it sets up a circulating current between the two
transformers. The result is that the voltage of the PARALLELED transformers
is Greater than 14.9KV and LESS than 15KV. Not only does this lower the
output voltage, but there is POWER Lost, because some of the current is
being circulated and NOT made available to the load. In other words, this
scenario not only lowers the voltage rating, it also lowers the Combined
Current Rating (It will be LESS than the sum of the rated currents).
You will find greater variations Between Various Brands than you will
between different instances of the Same Brand. The only way you can be sure
that all of them are giving out the same voltage is to measure them and
compare. Also, realize that different Brands DO things slightly
differently. Some brands (or Models WITHIN a Brand) use differing
strategies in designing what on the OUTSIDE Appears to Be Just About The
Same.
There ARE some things you can do to try REDUCE the Lost Power. What you
want to do is institute a means for LOAD SHARING. Right now the transformer
with the LOWEST IMPEDANCE is doing the GREATEST WORK. By the way, if the
Impedance MisMatch is TOO great (such as when ONE winding is DEFECTIVE),
then BOTH windings can be PERMANENTLY DAMAGED.
Here's a way to see if you have a MISMATCH problem. Remove ALL Neons from
the existing circuit. select ONE transformer to be your REFERENCE
Transformer. Connect a Second transformer with its PRIMARY terminals in
parallel with the Reference Transformer's Primary. Tie the Cases Together.
Connect a 1,000 Ohm (1K) 1/4 watt resistor between the LEFT hand side HV
terminals. Connect another 1,000 Ohm 1/4 watt resistor between the RIGHT
hand side HV terminals.Connect all primaries in Parallel. Power the circuit
ON for about a minute. If any resistor starts to Fry, turn power off
immediately. FRYING means you have a MisMatch in voltages of more than 40
volts. If it DIDN'T Fry, then after ONE minute of being ON, turn it OFF,
and then immediately touch both resistors. If they are Warm you have a
Minor Mismatch. If they are BOTH COOL to the touch, then You have no
Problem worth worrying about.
Repeat the Above MisMatch Test for ALL the Transformers you contemplate
Paralleling LATER.
If you DO have a MisMatch, we need to find out how great the MisMatch IS.
This requires an AC Voltmeter capable of measuring 1,000 volts. Put it on
the 1,000 Volt AC scale (Make SURE it is AC Scale!). Make sure the meter is
completely insulated and at least 4 inches away from ALL conducting
objects. (I put mine on a shoe box to make SURE it doesn't ARC to the
base!) Connect it across ONE of the Resistors. Turn Transformer on long
enough to see what the reading is. Write it down. Repeat for the Other
Resistor.
REPEAT process for ALL Transformers, ALWAYS using the same Reference
Transformer as ONE of the transformers in the test setup.
Use the HIGHEST value you got as the Working Value. Using the formula R=E/I
(where E is the Working Value, and I is .030), determine the Resistance
Required for the Load Sharing Resistor. Then determine the Actual Power
Dissipation: P=Working Value * .030
Multiply the answer for P by 2 to get the Minimum Suggested Safe Power
Rating for the Resistor. You will need to purchase TWO of these resistors
for EACH Transformer you want to Parallel. Here is how you connect these
suckers in the final design:
_______________________________________ HV Out
R R R R R
S S S S S
C C C C C
S S S S S
R R R R R
--------------------------------------- HV Out
C=Case of Transformer
S=Secondary HV Terminal of Transformer
R=Load Sharing Resistor
____ and ---- are Wires connecting the Circuit
Since the Transformers connect to the HV Rail through Resistors, Voltage
MisMatches are ABSORBED by the Resistors INSTEAD OF BY THE TRANSFORMERS
THEMSELVES.
The Downside to this technique is that it Increases the Effective Impedance
of the Transformer Set. The Upside is that it tends to make all
Transformers Share the Load, instead of the one with the Highest Voltage
getting stuck with doing the Lion's Share of the work.
By the Way, if you use the Load Sharing Technique you should REMOVE any
Resistor(s) you may have put in series with your Inductors, as the Load
Resistors now ALSO provide the SAME Service, and you don't want any
additional Resistance in the Circuit.
>
> The secondary is 1064 turns of # 24 wire on a 7" PVC pipe. The primary
is 3/8" copper tubing spaced 3/8" between tubes 6" inside dia. 30" outside
dia. 30 degree helix wound 18 turns tapped at turn 14. The capacitor is
..008 uf rolled polyethylene oil filled. The RQ spark gap is 8 gaps .030
each fan cooled. 2 chokes 2.5 uh each wire resistance 1.1 ohms. Toroid is
2 stainless metal bowls 12" dia. 2 safety gaps .250 gap from HV terminal
to the transformer case ground.
>
> Using power supply 15KV 90 ma I added another choke (100 uh 10.5 ohms
wire resistance) in series with the 2.5 uh choke. Total 102.5 uh 11.6
ohms. The output was reduced from 44" sparks to 39" sparks.
>
> Using power supply 15KV 90 ma I added another choke (190 uh 18 ohms wire
resistance) in series with the 2.5 uh and 100 uh chokes. Total 292.5 uh
28.5 ohms. The output was reduced from 39" to 30".
>
> I removed all 3 chokes on each HV terminals and the secondary spark
output is 44" using 15K 90 ma power supply. I added a 10 ohm resistor to
the HV terminals where the chokes were and the output was reduced from 44"
to 40". The output with a 10 ohms resistor is about the same as with 11.6
ohms wire resistance using 2 chokes.
>
***The Chokes protect the Transformers, but at a Price. When the Spark Gap
Fires, the resistance of the Gap decreases drastically. You would not be
too far off if you think of the Spark as causing the resistance of the Gap
to go to ZERO Ohms. This Dumps the Energy that was in the Capacitors into
the Tesla Primary (That's What We WANT!), but as a Side Effect, we have
just Shorted Out the Transformers (That are luckily in series with Mr.
Inductor). The Inductor does not Like Rapid Changes in Current Through
Itself. But wait a second, aren't the Inductors in series with the Neon's
Secondary winding? And isn't THAT an inductor TOO? (You Betcha!). HA! but
you thought of that and installed Filter Capacitors from the Inductors to
Ground or the opposite side of the Secondary. In any case, the REVERSE
VOLTAGE that results from the Magnetic Action over here just got stored in
THIS Filter Capacitor. You must NOW REMOVE this Charge before the
Transformer can recharge the Big Guy Capacitors (that are now Discharged
and acting an Awful Lot Like a Dead Short Themselves). Hmmm. All this
Reaction Stuff going on a couple of microseconds after the Gap Fires Looks
an Awful Lot Like Wasted Energy to ME! (IT IS!) You don't like that Side
Effect, but that's the Trade-Off, and you live with it until you come up
with a Better Way.
> Using power supply 15KV 150 ma I added another .008 uf capacitor in
parallel with the other .008 uf capacitor. Also using all 3 chokes in
series on each HV terminal. The secondary output sparks got much hotter
and much louder but not longer. Output is 30" sparks. The 3 chokes in
series are physical spaced 2" apart. Sparks are jumping between all the
chokes and also threw the choke windings. 1 neon shorted out and had to be
replaced. Tried again and another neon shorted out and had to be replaced.
>
*** Ditto. I rest my case.
> Both neons transformers that shorted were Franceformers. Both
transformers shorted only on one side. The side that shorted was the
capacitor side of the LC circuit. They were both in the exact same
location among the 5 transformers that were in parallel. With the
transformers in 1, 2, 3, 4, 5 order and the spark gap in parallel with
transformer # 5 it was the # 1 transformer that shorted out. The safety
gaps were connected across transformer 5. The LC circuit is connected
across transformer 5. The spark gap is connected across transformer 5. It
seem logical that any RF or HV feedback from the TC would reach transformer
5 first where all the safeties are connected. Transformer # 1 is the
farthest away them the safeties. What ever caused transformer # 1 to short
had to pass 4 other transformers to get to # 1. I moved both safety gaps
from transformer 5 to transformer 1. Replaced transformer 1 and tried
again.
>
*** Red Herring. The Transformers are all in Direct Parallel (THAT is most
likely the Real Problem, and I discussed Load Sharing Up Above Already). In
a Parallel Circuit ALL items are FORCED to have EXACTLY the SAME VOLTAGE
whether they like that fact or not. If there is any ORDER to WHICH
Transformer is Going To Go Belly Up Next, it is NOT due so much to its
physical location, but to the fact that when stressed with the SAME EXACT
VOLTAGE <ONE> OF THEM ARCS INSIDE AND THE OTHERS DON'T.
> Again transformer # 1 shorted out on the capacitor side of the LC
circuit. Another Franceformer brand.
>
> I replaced the bad transformer. Reduced the safety gaps from .250 to
..187. Moved the RQ spark gap from transformer 5 to transformer 1. I
still
have all 3 chokes in series with the LC circuit and connected to
transformer # 5. Try again. After about 10 seconds transformer # 1
shorted out but this time not on the capacitor side of the LC circuit. This
time I fried a Jefferson Electric transformer. An arc struck the spark gap
fan motor and shorted it out too. I'm not having very good luck.
>
***It isn't Luck, its Physics with a little Statistical Randomness that
makes it look like a Moving Target. ANY time we Coilers use a Neon
Transformer we are Gamblin' with the Odds because of that Case Center Tap
Problem. It is the Single Greatest Cause of Grief and Frustration, because
just when you think you've got the Perfect Neon... ZAP! Your Neon's Fried!
> It must be the capacitors. Too much capacitance? I didn't have this
problem with 1 capacitor.
>
*** Nah, C'mon, THINK about it. You didn't have this problem until you
decided to Parallel Some More Transformers into the Equation. What you did
was increase the number of Neons into the Statistical part of the Equation,
and with each one the problem got just a BIT more Aggravated. If ONE
transformer has a 50% chance of Failing Miserably, then with 5 transformers
it would almost take a Miracle NOT to have <One> Fail. When one DOES fail
and they are in Parallel, there is a certain amount of damage that is also
visited upon the OTHER transformers, because in a Parallel Circuit if ONE
of them goes SHORT, the others DUMP their current into THAT one, and they
ALL get damage due to the overload. It's a Bummer, but would you REALLY
rather have Any Other Hobby in the World?
> Gary Weaver
If all else fails, try something else.
Fr. Tom McGahee