[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: power v energy measurements, was Re: SSTC does 10 foot sparks
Original poster: "Eastern Voltage Research Corporation" <dhmccauley-at-easternvoltageresearch-dot-com>
This energy stuff is just going to far. As a power engineer who designs
high power transmitters, high power and high voltage power supplies, and
a boatload of DC-DC converters, I have not once ever heard anyone make a
reference to energy.
Its all about power!
> Sean -
> You do not have to agree with me to be right. As I mentioned before in the
> past I have used the word "power" incorrectly. This is very easy to do and
> it occurs in todays literature all the time. For example power cannot be
> consumed. This is why electric power companies do not sell power, they
> energy. Some coilers have said that the utility "demand charge" is selling
> power. This is not correct. The demand charge is a rental charge for large
> transformers and related switchgear.
> "How do I propose to use energy?" There are many possibilities. However,
> believe the best way to compare Tesla coils is to do it the energy way,
> the power way. I will give an example using a small coil I built and
> I don't have a SSTC to make a comparison but I know there are many
> who have both types who could easily do the tests and make the comparison.
> The tests consist of finding the TC input energy by connecting a wattmeter
> to the input of the TC. This will give you input watts per second
> You then turn up the variac so you have 120 watt seconds input and adjust
> the spark output for a continuous 120 sparks per second. You will then
> 120 watt seconds / 120 sparks per second giving you "one joule per spark"
> or "spark inches per joule of enrgy". I did this for my small TC and
> obtained 8.25 inches per joule. If you perform this test with with any
> SPTC or SSTC you will have a fair energy comparison of the Tesla coils.
> Of course the 120 sparks per second would have to be changed to the actual
> number per second.
> As I have mentioned in the past this leaves a lot to be desired and I am
> open to all suggestions. When larger coils are tested you will find that
> "spark length per joule" is much shorter but there is a good reason for
> which can be discussed later.
> This test also gives you some other interesting numbers about your TC. For
> example with my coil I found the energy in the 12" toroid (about 13
> picofarads) was 1 joule per spark. This gave me
> Secondary voltage = .5 x sqrt(joules/Cs)
> = .5 x sqrt(1joule / 13^-12)
> Secondary voltage = 392 KV at 100% eff.
> I assumed the secondary voltage eff was about 50% so the secondary voltage
> Secondary voltage = 392 x .5 = 196 KV
> If I connected an ammeter to the ground wire of the secondary coil I would
> Secondary current = joules/voltage = 1/196000
> Secondary current = 5.1 ua
> Note that this is the average (RMS) current in the secondary of my small
> coil. The actual peak current would be much greater. If I found the
> current by test was larger I could then find the true secondary voltage
> which would be higher than 196 KV.
> You can find even more TC parameters if you use energy instead of power
> rating your coils.
> John Couture
> ----- Original Message -----
> From: "Tesla list" <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Tuesday, June 22, 2004 9:15 PM
> Subject: power v energy measurements, was Re: SSTC does 10 foot sparks
> > Original poster: Sean Taylor <sstaylor-at-uiuc.edu>
> > John, I'm not really in agreement with you, the examples I gave
> > (specifically the 30 MJ) were to illustrate that two different coils,
> > consuming vast differences in power, can be given the same "energy
> > rating". How do you propose to use energy? Would you like to use
> > per bang, or energy over a certain amount of time? Both of those can
> > translated into power. What specific measurement of energy did you
> > mind?
> > Any meter, when used on a TC, will have fluctuations in the reading
> > the target a streamer happens to be striking at that moment. If a
> > meter is used, then the power will jump all over the place. The best
> > can do is to estimate an average power, where it seems that the needle
> > most of the time, or more accurately is expected to be most of the
> > I believe that strict energy comparisons have no place in comparing TCs
> > without another parameter to give more information (as in my example
> > in my first post on this topic - two very different TCs with the "same"
> > energy).
> > In your reply to Steve, you wrote:
> > Power output can be greater than power input
> > Power is in watts, average watts, peak watts, volt amps,
> > Energy output can not be greater than energy input
> > Energy is in watt seconds or joules*
> > The power input can be in many forms as I mentioned in my post
> > Gerry.
> > The energy input can be in only one form and that is watt
> > (joules).*
> > Power factor is involved with TC power ratings
> > Power factor is not involved with TC energy ratings.* Why??
> > I would say all but three of these statments are false (when taken in
> > certain ways). I would consider the three true statements to be the
> > marked with an *. Power output can be greater than power input, if you
> > speaking of peak power. Power is not in volt amps - that is apparent
> > power. Just power is Watts, and only watts. Units themselves cannot
> > average, peak, etc., only a quantity can. I know this is beginning to
> > into semantics, but you state that energy only comes in one form, and
> > same is true of power. It's always just Watts (or some equivalent
> > nothing else. The power input can't be in many forms, but the
> > can be *represented* in a few different ways, and I think that's where
> > confusion lies. As I said before, each representation (peak, average,
> > etc.) has it's place in each application. For comparison purposes in
> > TC world, we'll want to be using average power for the input.
> > Power factor doesn't/shouldn't come in to play here because power is
> > - regardless of the power facter. Apparent power on the other hand
> > current * voltage), will change with the power factor, given a constant
> > power. So if we know exactly how much work is being done by a system,
> > can calculate the apparent power based on the power factor.
> > For most of us, it is hard to get a good idea of what the real power is
> > because all we have is a voltmeter and ammeter, and they tell us
> > the phase relationship, and thus nothing of the power factor. All we
> > then calculate is the the apparent power and all we can do with this is
> > an approximation of the real power. As Steve said, he is drawing less
> > 20 A at 240 volts, so the apparent power must be less than 4800 VA, and
> > real power cannot exceed the apparent power, so it must be less than
> > (note the unit change - Watts != VA !!!).
> > Now, to make the leap to energy, well, the problem is how?? As I
> > asked, which energy did you want to measure? Even fewer of us have the
> > neccesary equipment to measure energy directly (aside from the energy
> > on the outside of our house). You wrote in another email "Energy is
> > involved with reactive powers.", while it most certainly is!!! It is
> > transferred in one direction though, because it continuously is
> > in to and out of the reactive compenent, and part of it gets wasted as
> > each time that happens (in the real, non-ideal world).
> > Anyway, this discussion is starting to get a bit OT, if you want to
> > continue it with me, please reply off list.
> > Sean Taylor
> > Urbana, IL
> > On Tue, 22 Jun 2004 08:29:32 -0600, Tesla list <tesla-at-pupman-dot-com>
> > >Original poster: "John Couture" <johncouture-at-bellsouth-dot-net> Sean -
> > >
> > >Thank you for your reply. It appears that you are in agreement with
> > >was recommending and that is to use energy instead of power to rate
> > >Tesla coils. You said your TC was 30 MJ which is rating your coil in
> > >of energy.
> > >
> > >I agree with you that to compare energy and power is utterly useless.
> > >is like
> > >comparing apples and oranges. This thread discusses the comparing of
> > >coils not the comparing of power and energy. I recommend that coilers
> > >energy instead of power to compare their coils which is what you are
> > >
> > >There are many coilers that use their wattmeters to measure several TC
> > >parameters. However, I see no problem in your using your wattmeter to
> > >measure only average watts.
> > >
> > >Refer to my reply to Steven regarding your mention of imaginary power
> > >factor). Steven was commenting on power factors.
> > >
> > >John Couture
> > >