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Re: SSTC does 10 foot sparks
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.
---------- 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>
>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
>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
>>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
>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
> "Peak power out"
>>larger than "peak power in" unless there is a time difference between the
>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
>>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
>>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
> 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,
>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).