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*To*: tesla-at-pupman-dot-com*Subject*: Re: power v energy measurements, was Re: SSTC does 10 foot sparks*From*: "Tesla list" <tesla-at-pupman-dot-com>*Date*: Wed, 23 Jun 2004 16:54:12 -0600*Resent-Date*: Wed, 23 Jun 2004 16:58:51 -0600*Resent-From*: tesla-at-pupman-dot-com*Resent-Message-ID*: <rw3MJD.A.GI.rsg2AB-at-poodle>*Resent-Sender*: tesla-request-at-pupman-dot-com

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! Dan > 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 sell > 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, I > believe the best way to compare Tesla coils is to do it the energy way, not > the power way. I will give an example using a small coil I built and tested. > I don't have a SSTC to make a comparison but I know there are many coilers > 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 (joules). > 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 have > 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 small > 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 the > "spark length per joule" is much shorter but there is a good reason for this > 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 > was > Secondary voltage = 392 x .5 = 196 KV > > If I connected an ammeter to the ground wire of the secondary coil I would > get > 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 average > 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 for > 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 energy > > per bang, or energy over a certain amount of time? Both of those can be > > translated into power. What specific measurement of energy did you have > in > > mind? > > > > Any meter, when used on a TC, will have fluctuations in the reading with > > the target a streamer happens to be striking at that moment. If a power > > meter is used, then the power will jump all over the place. The best we > > can do is to estimate an average power, where it seems that the needle is > > most of the time, or more accurately is expected to be most of the time. > > I believe that strict energy comparisons have no place in comparing TCs > > without another parameter to give more information (as in my example cited > > 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, > etc. > > 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 to > > Gerry. > > The energy input can be in only one form and that is watt seconds > > (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 ones > > marked with an *. Power output can be greater than power input, if you > are > > speaking of peak power. Power is not in volt amps - that is apparent > > power. Just power is Watts, and only watts. Units themselves cannot be > > average, peak, etc., only a quantity can. I know this is beginning to get > > into semantics, but you state that energy only comes in one form, and the > > same is true of power. It's always just Watts (or some equivalent unit), > > nothing else. The power input can't be in many forms, but the measurement > > can be *represented* in a few different ways, and I think that's where the > > confusion lies. As I said before, each representation (peak, average, > > etc.) has it's place in each application. For comparison purposes in the > > 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 power > > - regardless of the power facter. Apparent power on the other hand > (simple > > 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, we > > 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 nothing > of > > the phase relationship, and thus nothing of the power factor. All we can > > then calculate is the the apparent power and all we can do with this is > get > > an approximation of the real power. As Steve said, he is drawing less > than > > 20 A at 240 volts, so the apparent power must be less than 4800 VA, and > the > > real power cannot exceed the apparent power, so it must be less than 4800 > W > > (note the unit change - Watts != VA !!!). > > > > Now, to make the leap to energy, well, the problem is how?? As I already > > asked, which energy did you want to measure? Even fewer of us have the > > neccesary equipment to measure energy directly (aside from the energy > meter > > on the outside of our house). You wrote in another email "Energy is not > > involved with reactive powers.", while it most certainly is!!! It is not > > transferred in one direction though, because it continuously is > transferred > > in to and out of the reactive compenent, and part of it gets wasted as > heat > > 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> wrote: > > > > >Original poster: "John Couture" <johncouture-at-bellsouth-dot-net> Sean - > > > > > >Thank you for your reply. It appears that you are in agreement with what > I > > >was recommending and that is to use energy instead of power to rate your > > >Tesla coils. You said your TC was 30 MJ which is rating your coil in > joules > > >of energy. > > > > > >I agree with you that to compare energy and power is utterly useless. > This > > >is like > > >comparing apples and oranges. This thread discusses the comparing of > Tesla > > >coils not the comparing of power and energy. I recommend that coilers use > > >energy instead of power to compare their coils which is what you are > doing. > > > > > >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 > (power > > >factor). Steven was commenting on power factors. > > > > > >John Couture > > > > > > > >

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