Re: SSTC does 10 foot sparks

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "john cooper" <tesla-at-tesla-coil-dot-com> 

Very intersting stuff, how do we agree on a baseline or procedure for 
energy in/energy out measurements?  Or am I asking too much?  I'd be most 
interested in someone describing and identifying the equipment/measurement 
techinques necessary, then we can either follow those procedures or 'wave 
our dix in the air' claiming whatever.
John

---------- Original Message ----------------------------------
From: "Tesla list" <tesla-at-pupman-dot-com>
Date:  Sun, 20 Jun 2004 17:03:02 -0600

 >Original poster: Sean Taylor <sstaylor-at-uiuc.edu>
 >
 >John,
 >
 >I'm sure there will be many people replying to this, so I'll keep it as
 >short as possible :-)
 >
 >>I agree you cannot "get more average power out than what is coming in".
 >>However, it is very possible to get much more pulse power out than average
 >>power in.
 >
 >I completely agree, this is the whole thing with capacitor discharges, you
 >can charge them at a low rate, and discharge much faster to create high
 >peak currents.  This concept is used all over the place in technology.
 >
 >  With Steve's TC it appears that the average power in is about
 >>4800
 >>watts and the pulse power out is about 300 KW giving a power gain of 62.5 .
 >
 >The concept of "power gain" is a VERY misleading one.  Power is DEFINED as
 >energy transfer per unit time, so by definition when comparing two powers,
 >unless otherwise stated, you are comparing a total power transfer.  The
 >difference is when you consider peak power, which is the instantaneous RATE
 >of energy transfer.
 >
 >>With a potential power output of 300 KW it is obvious that a very
 >>long spark would be possible depending on the TC design. That is why using
 >>power instead of energy units is not good for rating Tesla coils. It can
 >>exagerate the output possibilities of a coil so you have to be very specific
 >>about the input conditions.. If you use energy units you will not have this
 >>type of problem. The energy output units will always be less than the input
 >>units.
 >
 >Not necesarily true.  Energy output at a chosen time (perhaps between
 >bangs) will be much less, about 0, than the input energy.  Also, saying
 >input or output energy entails energy transfer, implying a rate, not just a
 >quantity of energy.  With any sort of energy storage device, energy in and
 >out can be very different from each other.
 >
 >
 >>"Peak power out will be larger than peak power in" is another example of the
 >>confusion caused by using power with Tesla coils.
 >
 >I wouldn't call this a confusion so much as a difference of measurement
 >techniques.
 >
 >  "Peak power out"
 >>cannot be
 >>larger than "peak power in" unless there is a time difference between the
 >>two
 >>stated powers.
 >
 >Peak power out and peak power in can be very different, and either one can
 >be greater than the other.  I think what you mean by "unless there is a
 >time difference . . . " is that the total time that the power is measured
 >over is different for the input and output.  You can have a single spike of
 >power at say 10W, and measure for however long you want, and still only
 >have a 10W peak, the time doesn't matter.  I think you are confusing
 >integrating over the two times (yielding energy) rather than recording the
 >peak power transfer.
 >
 >  This means bringing in time into the process which gets
 >>you
 >>into an energy process.
 >
 >Not really, depending on how you use the time.  Dividing by time will give
 >an average power transferred per time, multiplying/integrating will give
 >you an amount of energy transferred.
 >
 >  It would be preferable to say that "Peak power
 >>out
 >>will be larger than average power in".  This still requires more
 >>explanation. The time period involved in the output vs the time period
 >>involved in the input. And we are back again into energy out vs energy in.
 >
 >A peak power is an instantaneous event, there is no measurement over time
 >for the peak.  It happens, and it's over with, there is no amount of time
 >that matters.  The time that energy is being transferred overall may be
 >(and will be) different between the input and output, but this is not a
 >concern for peak power measurements, and is the whole essence of power
 >storage devices/pulse discharges.  It's why a TC works!
 >
 >
 >>Note that when using average power that you are adding time to the power
 >>units which brings you into the energy unit solution. This has caused great
 >>confusion for coilers in the past. Average power is actually energy because
 >>you have to use time to find the average power.
 >
 >Again, see above, just because you use time doesn't mean you get energy.
 >There is a big difference between average power and energy.  Average power
 >is calcualted from W/sec, over a specified period of time yielding Watts
 >again.  Energy is just a specific quantity of energy, no time involved
 >whatsoever.
 >
 >  In other words when you
 >>connect a wattmeter to the input of a TC you are measuring many parameters
 >>depending on how you want to use them. For example the wattmeter gives you
 >>at the TC input
 >>
 >>    1.  wattage
 >>    2.  average wattage
 >>    3.  peak wattage
 >>    4.  instantaneous wattage
 >>    5.  volt amps
 >>    6.  RMS wattage ??
 >
 >Strictly speaking, wattmeter doesn't give you all these things, it gives
 >you one:  average "wattage", or power.  Some, with storage functions, will
 >give you peak power, but this can be the peak over 1 cycle, or the peak
 >instantaneous power.  In an AC circuit, you have instantaneous power, which
 >is defined as instantaneous current times instantaneous voltage, but is not
 >very meaningful in terms of what is actually going on because both I and V
 >are going positive and negative continuously.  This is where average power
 >comes in - the average over one AC cycle.
 >
 >Because of non-resistive loads, the power transfer can be going in to or
 >out of the "load", meaning the instantaneous power is positive sometimes,
 >negative other times, so an average "power" is used to represent what work
 >is actually being done - also know as the real power, measured in Watts.
 >The RMS current and RMS voltage, considered without and phase difference is
 >the "apparent power" - Volt-Amps, and often most devices are rated to a
 >certain VA because the wire has to handle a certain amount of current, and
 >it doesn't care if it's in phase with voltage or not, there is still that
 >amount of current to be passes.  The imaginary power, measured in VA
 >reactive, is just the part of the current that is purely reactive,
 >imaginary, or 90 degrees out of phase with the voltage that does absolutely
 >no work whatsoever, and can't because the average power is zero - half the
 >time energy is flowing into the load, the other half out of the load, the
 >effective energy transfer is zero, and power is zero.
 >
 >>Correctly using all of these parameters can be very confusing. You can avoid
 >>all of the above confusion by properly using energy units to rate Tesla
 >>coils. If the wattmeter is used as an energy meter you have to do some calcs
 >>and you end up with different numbers compared to using it as a power meter.
 >>For example a 100 watt wattmeter will give you 50, 100, 200, etc, watt
 >>seconds when used as an energy meter if the times are 1/2, 1, 2, etc,
 >>seconds.
 >
 >So how is this less confusing than using power?  I can run my 1" TC for
 >days on end and claim that "consumed" more than 30 MJ.  Then I'll go run my
 >15" 10 kVA pig coil for under an hour, and it'll "consume" the same amount
 >of energy.  So what's the point?  I can also tell you that one coil has a
 >bang energy of 2 J, and another 10 J.  If the breakrate of the first is 600
 >bps, and the second is 120 bps, they "consume" the same amount of energy
 >per time, or use the same power.  I can also tell you that the National
 >Ignition Facility at LLNL consumes over 2 MJ in one shot, much less than
 >one second, while running my small TC will take over 5.5 hours to process
 >the same amount of energy.  So, how do you propose we use energy to compare
 >TCs?  I'm not seeing how it would work.
 >
 >
 >>There is a much more to comparing power vs energy and I find that in some of
 >>my past posts I have used the words incorrectly. Coilers are correct when
 >>they say that power and energy can muddy the waters.
 >
 >I think trying to compare energy and power is utterly useless.  I think we
 >can all agree that when we talk about power input, we are talking about
 >average power, or just a rate of energy transfer into our coils.  Steve's
 >less than 4800 W input is the average power going into his coil, and also
 >must leave at the same rate, whether it be in the form of heat, light, or
 >electricity.  However, instead of entering at a (relatively) constant rate
 >as happens on the 60 Hz line (since 60 Hz is slow compared to RF), the
 >power is leaving in large pulses that happen as often as he dictates by the
 >breakrate of the coil, and while these peak powers occur at a lower duty
 >cycle than the input power has, there are much larger peak powers (maximum
 >of instantaneous power) present on the output.
 >
 >Okay, so that wasn't as short as I expected, but I hope that clears up some
 >nomenclature questions for everbody (and maybe for myself, as I'll probably
 >be corrected on some things I wrote).
 >
 >Sean Taylor
 >Urbana, IL
 >
 >
 >
 >