[Prev][Next][Index][Thread]
Re: NEW break-rate/power tests
Hello John, all,
Very interesting results. My comments are interspread below.
>I did some tests at a higher power level. First I installed a .0148uF
>cap with the 120 bps sync gap, then compared with the 400 bps
>rotary gap. At 1370 watts, the spark reached 54" at 120 bps, but
>at 400 bps, the spark could not reach 54" even at 2000 watts. But
>it came close. However, the spark was brighter and more
>flamelike at the high break-rate, and wanted to go upwards towards
>the ceiling. The ceiling is 36" above the top of the toroid.
>The sparks looked completely different at 120 bps.
>At this low break rate, the sparks were not as bright, but
>they tended to surge and grow, and emitted from different spots
>around the toroid. The sparks floated around slowly. The high
>break-rate sparks tended to be all about the same length and,
>seemed to want to remain together like a giant
>blow-torch or flame, and reminded me a little of tube coil sparks
>(high powered tube coil sparks of course).
While I am not using an RSG (yet), these results (spark
appearance) are very similar to what I have found and
posted a few weeks ago (although the how and why
mechanism might be a little different in my case).
<SNIP>
>Next I replaced the 1500 watt 14.4kV potential transformer with (2)
>1500 watt 7.2kV potential transformers in series for a "stiffer" power
>supply. With this set-up I got 54" sparks at 1000 watts at 120 bps.
>At 400 bps, the sparks were very bright, but never reached 54" but
>they hit the ceiling a lot and seemed more powerful than with the
>one transformer.
After hearing so many comments about low voltage/ high current
setups having higher losses and probably not so good an output
AND NOT being able to agree (because I have found it not to be
true, for me), this brought a smile to my face. During Johnīs
low voltage xformer test, he gets 54" sparks at 1000W (as
compared to 54" at a "HV" 1370W). This is the exact opposite
of what high voltage coilers are saying (:o)) !! A low voltage
coil may need more construction thoughts, but IT
DEFINATELY does NOT perform worse!!
>Then I replaced the 20" toroid with a 6" by 26" dryer duct toroid,
>This arrangement gave 58" sparks at 1050 watts, this I believe is
>a record for efficiency for my coils, based on my formula:
> spark length (inches) = 1.7*sqrt input power, wallplug (watts).
>The formula predicts 55", but this coil gave 58" sparks. I attribute
>the greater efficiency to the use of two transformers, which reduces
>the losses.
I think the higher the primary tank current is, the bigger the topload
should be (at least this seems to work for me).
>Note; those with NST powered systems are cautioned to never use
>the NST power rating written on the NST in my formula above.
>Many NST systems use resonant charging and actually draw double
>or more the NST rated power input. The only way to know the input
>power of any Tesla coil is to measure it with a suitable wattmeter.
>If a wattmeter is not available, at least use an ammeter, and multiply
>by the input voltage to obtain input VA (volt-amps). This will not
>correct for the power factor error, but will give a ballpark
>measurement. In my coils, input current distortions and/or high
>frequency components did not seem to affect the meter accuracy
>by much. My formula above uses true input wallplug power. I
>measure the power before any variacs, ballasts, etc.
I agree with John here. I, myself, have used the VA ratings
somewhat carelessly (although never the printed rating).
I am not using a reso cap. I have always wondered about the
NST (coiler) VA ratings. If you have a 7.5kV NST with say
75mA rating, the formula V*A = 7500*0.075A = 562VA.
HOWEVER, the NST will give you EITHER 7500V OR 75mA,
but never both. The 75mA rating is a short circuit rating, which
means the voltage is zero or almost zero! Every shunt limited
xformer works this way. The input current is (unless
compensated) not a very good way to measure actual input
VA, because you are not considering all losses. The best way
would be to measure the HV xformerīs secondary voltage and
current, which probably isnīt an easy task (voltage and current
are constantly surging up and down), either. So, the primary
(mains input) VA will always be a lot higher than the actual
VA that is feeding the coil. Comparing coils and results this
way is okay, but it does NOT (I think) give you an accurate
view of what the real VA is, that is feeding the coil.
>Table of results:
>Cap (uF) bps watts toroid (inches) spark (inches)
<Snipped HV xformers>
>.0148 120 1000 (2) xfrmers 5 x 20 54
>.0148 120 1050 (2) xfrmers 6 x 26 58
>.0148 400 2000 (2) xfmers 6 x 26 went to ceiling
> but approached 58
>.0148 600 2000 (2) xfrmers 6 x 26 not weaker
>.0148 400 1000 (2) xfrmers 6 x 26 36 (low cap
Volts)
>.0148 400 1050 (2) xfrmers 5 x 20 41
>.007 400 1000 (1) xfrmer 3 x 10 30
This I find extremely interesting. The spark LENGTH does
NOT change with BPS. The 120bps 1050VA created a
58" streamer and the 400bps 2000W was barely able to
come up with the same results. (Which is pretty much what
John wrote) I, for myself, am always looking for longest and
NOT "best looking" sparks.
>Also, the energy stored in toroid (per bang) is lower.
Agreed. Plus as I mentioned above, the greater the tank
amperage, the bigger the topload should be (meaning more
stored Joules in the topload). I also think the low voltage,
high current setups benefit from the high Lsec to Lpri ratios.#
I know resonance believers wonīt like this, tho :o).
I havenīt been able to give this much thought, but it seems a
universal sparklength equation (Johnīs empirical equation
seems to work great) has to take the following parameters
into account:
a.) LRatio (pri to sec)
b.) Primary tank current
c.) Ctopload
d.) Input joules
e.) Breakrate
I donīt think the higher the TC output voltage necessarily
means the longer the spark is. The ability of the coil to
feed and keep up a created ion channel leads to long
sparks (in my opinion).
>For a high break-rate system to outperform, it has to make up for
>all the above losses and then some more by using ion channel
>spark-growth----can it do it? Obviously, not in coils of the size I'm
>testing (up to 2000 watts). I do not know how much of the high
>break-rate under-performance results from losses, and how much
>may be inherent to high break-rates (if any). I would not be
>surprised if the losses at high break-rates are much lower
>(relatively speaking) in large coils compared to small ones.
Might it be possible that it has something to do with the
cap DISCHARGE time? In a high break rate system one
should consider that not only does the cap have very little
time to charge (which is why the cap value has to go down
for a given xformer VA rating at higher BPS values), but it
also has very little time to discharge.?!?
Coiler greets from germany,
Reinhard