Current and voltage Waveforms

[mivey]

Tends to make me question math as being the universal language

But the math is what led to the translation of what the writer meant. Look logically at what you would do with the math using your own terminology and it makes it clear what the author was doing, even though he did not state it clearly in english.

Same can be said for some of the other terms he uses in the book. Look at the equations he uses and you can translate into local terminology. The underlying math is the same in either language.

 

[Smart $]

But the math is what led to the translation of what the writer meant. Look logically at what you would do with the math using your own terminology and it makes it clear what the author was doing, even though he did not state it clearly in english.

Same can be said for some of the other terms he uses in the book. Look at the equations he uses and you can translate into local terminology. The underlying math is the same in either language.

I'm not saying it's gibberish, mind you

But the underlying ideas and meanings in any language are the same if interpretted correctly

 

[mivey]

But the underlying ideas and meanings in any language are the same if interpretted correctly

Absolutely. And by saying math is a universal language for a particular subject, we are saying the underlying ideas and meanings are purely mathematical in nature.

While not all ideas and meanings are purely mathematical in nature, those that are will be the same in any language. Almost universally, the ideas that get argued are those that are not pure math. You can't argue math as it is just a physical reality (well, it would probably get argued here :grin.

How you apply that math on the other hand...

 

[Smart $]

Absolutely. And by saying math is a universal language for a particular subject, we are saying the underlying ideas and meanings are purely mathematical in nature.

While not all ideas and meanings are purely mathematical in nature, those that are will be the same in any language. Almost universally, the ideas that get argued are those that are not pure math. You can't argue math as it is just a physical reality (well, it would probably get argued here :grin.

How you apply that math on the other hand...

Isn't the premise of math itself an argument :roll: prior to finding a solution.

 

[mivey]

Isn't the premise of math itself an argument :roll: prior to finding a solution.

No. Math is a universal reality. It begins with the simplest things, like maybe a binary sequence. A binary counting system will be recognized by any mathematician, regardless of the symbols, apples, oranges, or whatever is used. In fact, binary code was used on the Voyager Golden Record because it is such a universal way to communicate.

Move forward to light speed. A caveman could have discovered the speed of light and might only be able to express what he is talking about with ugs, hand-waving, and pictures. Suppose he wrote down the speed of light using pictures of Fred, Wilma, Pebbles, Dino, and the rest of the gang. Assuming he did the math correctly, we should be able to translate his ancient number system into ours because the speed of light is a given.

 

[Smart $]

No...

From my perspective, you take math, as the subject of humor, a bit too seriously

 

[mivey]

From my perspective, you take math, as the subject of humor, a bit too seriously

P(#26|mood~)=0.50 :grin:

 

[robbietan]

http://books.google.com/books?id=h1...&resnum=1&ved=0CCUQ6AEwAA#v=onepage&q&f=false

Here in 214. page the current and voltage waveforms are given as sum of two different sinus waves, why?

İn fact any sinusoidal current or voltage is sum of all its harmonics and fundamental wave, so why is there indices such as m,n,p instead of only n?
İs not it bizarre? why does this book takes a current as sum of two different (frequency ) sinus waves?

the equations are used to compute for power factor when the voltage and current have harmonics. the summation symbol on the left Σ says that to get the whole picture, all harmonic numbers present in the waveform must be computed in order to get an accurate power factor number. so both the current and voltage waveforms are the sum of all the harmonic frequencies and the fundamental frequency inside them.

 

[mivey]

the equations are used to compute for power factor when the voltage and current have harmonics. the summation symbol on the left Σ says that to get the whole picture, all harmonic numbers present in the waveform must be computed in order to get an accurate power factor number. so both the current and voltage waveforms are the sum of all the harmonic frequencies and the fundamental frequency inside them.

So while you agree with what the OP already said:

İn fact any sinusoidal current or voltage is sum of all its harmonics and fundamental wave

you did not address his question

so why is there indices such as m,n,p instead of only n?
İs not it bizarre? why does this book takes a current as sum of two different (frequency ) sinus waves?

He wanted to know why there were multiple order-terms instead of just one. Normally, we are just looking at one set of voltages and one set of currents for a given load and you would just have one symbol to represent harmonic orders (like "n").

IMO, the additional indices were for other loads (like the parallel capacitor) connected to the same source as the load being studied. See #17 & #19.

As for the power factor, the author goes on to describe the solution for optimizing the use of capacitors to compensate for the load's non-unity p.f.. The optimal solution was one that minimizes the apparent power supplied by the source, and in doing so provides the maximum p.f. and minimum source current. This was accomplished by setting the derivative of the apparent power equation for the source to zero.

 

[Mayimbe]

P(#26|mood~)=0.50 :grin:

:roll: Bayes?

P(#26|mood~)=(P(#26))int(P(mood~))/(P(mood~))

 

[Smart $]

...

IMO, the additional indices were for other loads (like the parallel capacitor) connected to the same source as the load being studied. See #17 & #19.

...

Perhaps I'm missing something (even taking "foriegn matter" into consideration ), but I do not see why the second summation term for current does not include a possible phase shift (there is no ϕ).

 

[electrics]

hey as far as I remember I had seen a site which declares that this has to do with the theorem regarding this subject and cited in the very same page of which I gave the link, it says something like
some of the harmonics are "common" and some are "uncommon", so every waveform has two component, common ones have nonzero harmonics uncommon ones have only one nonzero harmonics bla bla bla.
I didnt explore the subject but you can find the real answer by these words..common and uncommon harmonics...

 

[mivey]

Perhaps I'm missing something (even taking "foriegn matter" into consideration ), but I do not see why the second summation term for current does not include a possible phase shift (there is no ϕ).

My thought was that the phase shift was only of interest for the load under study. The other voltage and current harmonics terms being due to other loads that would have a different voltage and current from the load. However, I like the idea of common and uncommon harmonics as mentioned by electrics better as it is certainly a cleaner explanation. Unfortunately, the author did not elaborate on the equations.

...and cited in the very same page of which I gave the link...

What link? The author does not discuss common/uncommon harmonics in the book link you provided.

 

[Smart $]

My thought was that the phase shift was only of interest for the load under study. The other voltage and current harmonics terms being due to other loads that would have a different voltage and current from the load. ...

If that's the case, I don't see the need to include the "other" currents in the equation... yet including them without their phase shift would yield an inaccurate total: i(t)

I'm still not convinced enough to cross the fence

 

[robbietan]

So while you agree with what the OP already said:
you did not address his questionHe wanted to know why there were multiple order-terms instead of just one. Normally, we are just looking at one set of voltages and one set of currents for a given load and you would just have one symbol to represent harmonic orders (like "n").

IMO, the additional indices were for other loads (like the parallel capacitor) connected to the same source as the load being studied. See #17 & #19.

the author (IMHO) just want to distinguish the different phase shifts present in the equation. That the phase shifts for the first part of the equation is different from the phase shifts in the second part of the equation.

 

[mivey]

If that's the case, I don't see the need to include the "other" currents in the equation... yet including them without their phase shift would yield an inaccurate total: i(t)

I'm still not convinced enough to cross the fence

I wouldn't bet my life either way. Just trying to find something that makes sense.

 

[mivey]

the author (IMHO) just want to distinguish the different phase shifts present in the equation. That the phase shifts for the first part of the equation is different from the phase shifts in the second part of the equation.

That may be, but does not explain why he used "n" in the first parts for both u & i but "m" & "p" for the second parts. Or does it? I'm too tired to think about it right now.