Re: power v energy measurements, was Re: SSTC does 10 foot sparks

["Tesla list" <tesla-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
 >  > >
 >
 >
 >
 >
 >