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Re: power v energy measurements, was Re: SSTC does 10 foot sparks
Original poster: Bart Anderson <tesla111-at-sbcglobal-dot-net>
Hi All,
I too have taken the side of finding this topic pretty much useless. The
battle of power and energy comes up on the TCML far too often. There are
those here who just love to research the physics (I'm in that category),
yet others find that stuff boring. Even though I love the research, it is
clear we will never be able to compare coils one for one. The best we can
do as a "comparison" is simple average power measurements for a given spark
length (and maybe a few tid bits about break rates and losses). Efficiency
comparisons are not possible in this type of forum (as great as it is).
Those type of comparisons have to be performed in a controlled project
environment with the same engineers making comparisons with whatever units
of measure they choose to define. But not across a large forum like this.
There are just too many dynamics (and I'm not talking only of coil dynamics).
It is fun to read the posts however (kind of a love/hate thing).
Take care,
Bart
Tesla list wrote:
>Original poster: "Malcolm Watts" <m.j.watts-at-massey.ac.nz>
>On 23 Jun 2004, at 16:54, Tesla list wrote:
>
> > 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
>
> Absolutely agree. All the appliances I've ever come across are
>rated in units of power based on a figure such as continuous
>consumption (e.g. light bulbs, heaters) or maximum (peak) power
>consumption (e.g. audio amplifiers) when running from a more-or-less
>fixed voltage (e.g. 240VAC mains). I find nothing confusing about
>such ratings. For one thing, it tells me what fuse ratings should
>apply.
> The power consumption of a Tesla Coil inevitably varies but
>knowing that one can obtain several strikes of a certain length over
>some nominated period of time without popping a breaker of a
>particular current rating is the figure I'd consider relevant and
>useful. I once made a statement about sparklength/energy rating, a
>move I left behind years ago after developing a much deeper
>understanding of the dynamics involved. The passage below reads like
>a supreme exercise in obfuscation to me.
>
>Malcolm
>
>
> >
> >
> > > 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 > > > > > > >
> > >
> >
> >
> >
>