Re: 20 joules at 100 bps vs 4 joules at 500 bps

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: FutureT@xxxxxxx 

In a message dated 8/8/05 7:42:33 PM Eastern Daylight Time, 
tesla@xxxxxxxxxx writes:


> Hi,
>
> The Freau formula's "1.7" factor is for NSTs.  NSTs are very power
> limited and predictable so the formula works over a wide variety of systems.


Terry,

This 1.7 factor works for many types of transformers not just NST's.
I didn't design the formula or the factor to be used only with NST's.
I never said or suggested that the user of the formula or the 1.7 factor
should use the nameplate rating.  I always used wallplug *input
power* in the formula.  But I also stated at times that it was OK
to use VA for larger pig type coils.

Consider these examples:

  Richard Hull's Nemesis coil.... This drew about 11kW or 11kVA
somewhere in that ballpark.  Using the 1.7 factor gives 14.8 feet.
Richard measured 15 foot sparks.  This is pretty close.

  Greg Leyh's older large coil....  This drew about 32kW or maybe
32VA.  Using the 1.7 factor gives 25 feet.  Indeed his sparks were
about 25 feet.

  Greg's Electrum coil ....  This drew about 130kW or 130kVA maybe.
Using the 1.7 factor gives 51 feet.  The coil gave about 50 foot
sparks.  A pretty good agreement.

Many other folks have found the formula using the 1.7 factor to
be accurate for pig type systems.  The formula also gives
good agreement for Ed Wingate's magnifier coil.  Remember
the formula is just a general guide for what kind of spark lengths
might be obtained at a certain input power (or VA).



> In the case of pole pigs, we can draw vastly more power that they are
> "rated" for....  We would need to know the "true" voltage, current,
> and power factor.  Often the voltage and an "averaged" current is
> metered, but to truly know the input power takes more metering
> equipment than most folks have at the time.


If a person draws 7kVA from a 1.5 kVA transformer and plugs
1.5kVA into the formula, then yes the formula will not give good
results.  Of course such action would be in error any way you
look at it.  The formula was designed to use actual input power
or VA.


> The "metering" problem is a big one!!  Big pole systems are hard to
> accurately measure true power without some pretty nice equipment.  At
> the low end, the fabulous $30 "will-a-watt" meter solved the problem
> below 1.8kW.  Above that, a wide band CT and one of those power
> "black boxes" is not cheap.  Traditionally, they used the pole
> transformer's rating as a standard.


I don't think this method of judging the input power (going by
the rating) was very common although it certainly was used
in certain cases.

John