thingmaker3,

Quote:
Your logical fallicy is called "the straw man argument." Nobody here claimed "phasor" was a substitution for "vector." The term "sub category" does not mean the same thing as "substitute."

I beg your pardon? Look at post #26 of this thread where you yourself say the following; "I think we've already decided amongst ourselves that they are the same. We've only got one hold-out." What were you talking about as being the same?

I'm curios: what is your native language?

I could ask you the same question. Did you not call phasors and vectors the same thing?

And you DO agree with me. You just call it something else.

Even a casual reading of this thread show that we are still in disagreement. Did you not read what author Krase says about phasors and vectors? Did you not understand my enumeration of the differences between them?

Ratch

 

Even a casual reading of this thread show that we are still in disagreement.

Even a casual reading would show the following.

You are (deliberately?) avoiding statements that could help you understand a world wide accepted definition.

You are deliberately avoiding questions designed specifically to aid understading. I asked for the 'magnitude' of a specific vector on Post #23

Since this is an electronics forum let us consider instead of the above triples, the vector space of all possible triples formed only from the characters 1 and 0 with the rules of addition that eg {1,0,1} ; {0,0,1} etc

1+1 = 0+0 =0
1+0 = 0+1 =1

I don't see an answer.

Incidentally is this vector space reported in you textbook on linear analysis?
Since there are an infinite number of vector spaces it must be a pretty good book to cover them all.

Phasors are vectors
Other types of vector are not phasors

It does the other members, especially those who are learning, a great disservice to espouse incorrect notions, especially without formal proof.

From Circuit Analysis, by Irving L Kosow, 1988, p. 446, "… Phasors may represent periodic sinusoidal and nonsinusoidal waveforms, as long as they are time varying.

Now this is just plain wrong and very very very misleading.

If you (or Mr Kosow) believe it correct, then perhaps you would display the phasor diagram for the very common situation in almost every piece of electronic equipment.

Draw a phasor diagram for the relationship between the magnetising current and a sinusoidal applied voltage in a ferrous cored transformer, taking core hysteresis into account.

Since I am following the rest of the EE community in showing a student that this is impossible in another thread here, I would sincerely like to avoid misleading him if I (we) are wrong.

 

Even a casual reading would show the following.

You are (deliberately?) avoiding statements that could help you understand a world wide accepted definition.

That's because he enjoys argument more than he enjoys learning.

Phasors are vectors
Other types of vector are not phasors

Not on the planet Ratch comes from...

It does the other members, especially those who are learning, a great disservice to espouse incorrect notions, especially without formal proof.

Other members? What other members? There is only Ratch, the disciples of Ratch, and one or two troublemakers who are so misguided as to diverge from the one true path of Ratchness.

Show him the evidence and he points at the grammar instead of looking at the evidene. Show him a clear example and changes definitions instead. Point out his fallacies and he commits more fallacies.

It's all cool though. He agrees 100% with me. He just won't admit it.

 

studiot,

Quote:
Even a casual reading of this thread show that we are still in disagreement.

Even a casual reading would show the following.

You are (deliberately?) avoiding statements that could help you understand a world wide accepted definition.

You are deliberately avoiding questions designed specifically to aid understading. I asked for the 'magnitude' of a specific vector on Post #23


Quote:
Since this is an electronics forum let us consider instead of the above triples, the vector space of all possible triples formed only from the characters 1 and 0 with the rules of addition that eg {1,0,1} ; {0,0,1} etc

1+1 = 0+0 =0
1+0 = 0+1 =1

I don't see an answer.

I believe you are trying to get me to say that since the vector space you defined in not geometric, then magnitude and direction are not defined.

Incidentally is this vector space reported in you textbook on linear analysis?
Since there are an infinite number of vector spaces it must be a pretty good book to cover them all.

I don't expect the book to cover all vector spaces, but it should cover phasors since they are so common in electrical engineering.

Phasors are vectors
Other types of vector are not phasors

I have no trouble with the second sentence. The first sentence is like saying "Bread is wheat". Like vector and phasor, bread and wheat are not interchangeable, even though bread and wheat might have some relationships with each other. Same with vector and phasor.

It does the other members, especially those who are learning, a great disservice to espouse incorrect notions, especially without formal proof.

And what incorrect "notion" is that? I gave the definition of a phasor. It is time-varying periodically rotating vector defined in the duplex plane. A definition does not need proof unless it contradicts itself. If it does not possess these properties, it is not a phasor.

Quote:
From Circuit Analysis, by Irving L Kosow, 1988, p. 446, "… Phasors may represent periodic sinusoidal and nonsinusoidal waveforms, as long as they are time varying.

Now this is just plain wrong and very very very misleading.
QUOTE]

How so? Every phasor I have come across has the properties Kosow enumerates.

If you (or Mr Kosow) believe it correct, then perhaps you would display the phasor diagram for the very common situation in almost every piece of electronic equipment.

Draw a phasor diagram for the relationship between the magnetising current and a sinusoidal applied voltage in a ferrous cored transformer, taking core hysteresis into account.

Since I don't have that kind of data readily available, and drawing is difficult to do here, I will answer your question verbally. You already specified a periodic timer-varying source voltage. Would not the resulting current also be a periodic time-varying function? If so, why could you not represent the voltage and current as phasors? This is done routinely in series and parallel AC circuits. What am I missing here?

Since I am following the rest of the EE community in showing a student that this is impossible in another thread here, I would sincerely like to avoid misleading him if I (we) are wrong.

Show me the thread.

Ratch

 

thingmaker3,

That's because he enjoys argument more than he enjoys learning.
Not on the planet Ratch comes from...

Attacking the messenger with the message.

Other members? What other members? There is only Ratch, the disciples of Ratch, and one or two troublemakers who are so misguided as to diverge from the one true path of Ratchness.

Everyone believes what they want to believe.l

Show him the evidence and he points at the grammar instead of looking at the evidene. Show him a clear example and changes definitions instead. Point out his fallacies and he commits more fallacies.

Nonsense, I have argued against the "evidence."

It's all cool though. He agrees 100% with me. He just won't admit it.

Not about calling a phasor a vector, I don't. Even though they have some vector-like properties. Kosow doesn't agree with you either.

Ratch

 

I gave the definition of a phasor. It is time-varying periodically rotating vector

Truth,

'Out of the mouths of babes'

A phasor is a vector .

Now that we have got that settled, let us agree on a working description so that I can show what I mean by saying Kosow is wrong.

Since you can't draw the graphs I will once we have a working description/definition.

 

studiot,

Quote:
I gave the definition of a phasor. It is time-varying periodically rotating vector


Truth,

'Out of the mouths of babes'

A phasor is a vector .

Now that we have got that settled, let us agree on a working description so that I can show what I mean by saying Kosow is wrong.

A phasor is a derived entity from rotating vectors. I still am not sure that a phasor can be called a vector. As in analogous example I gave previously, one does not refer to "bread" as wheat, even though it contains wheat and cannot exist without wheat. It is still something different than just wheat. That is what I, and I believe Kosow are saying about phasors.

Now that we have got that settled, let us agree on a working description so that I can show what I mean by saying Kosow is wrong.

We have an understanding, but not a complete agreement. Let's see what you have to say about Kosow.

Ratch

 

As in analogous example I gave previously, one does not refer to "bread" as wheat, even though it contains wheat and cannot exist without wheat.

Lepidoptera and Insectae are a better example. The relationship is sub-categorical.

It is good that you agree with me on all things, Ratch! I am happy that you have finally seen the light and come around. I look forward to our productive new relationship.

 

thingmaker3,

Lepidoptera and Insectae are a better example. The relationship is sub-categorical.

I believe the relationship of bread and wheat, which is an inclusive but unequal relationship is more appropriate.

It is good that you agree with me on all things, Ratch! I am happy that you have finally seen the light and come around. I look forward to our productive new relationship.

I see no reason to celebrate yet. I have not learned anything new that I did not know before. Specifically that phasors are rotating vectors. I still have doubts as to whether phasors can be regarded as vectors even though they are derived from vectors. Remember that Kosow believes it is stretching things a bit also.

Ratch

 

I believe the relationship of bread and wheat, which is an inclusive but unequal relationship is more appropriate.

So you believe all insects to be butterflies. How very strange of you.

I see no reason to celebrate yet. I have not learned anything new that I did not know before. Specifically that phasors are rotating vectors.

Yes. I'm happy you finally admit this to be the case. We should get together and open a bottle of wine. You buy. Don't be cheap.

I still have doubts as to whether phasors can be regarded as vectors even though they are derived from vectors. Remember that Kosow believes it is stretching things a bit also.

Kosow does not exist. You can't prove he exists.

 

thingmaker3,

So you believe all insects to be butterflies. How very strange of you.

Did I say that? Or is it a leap of faith on your part?

Yes. I'm happy you finally admit this to be the case. We should get together and open a bottle of wine. You buy. Don't be cheap.

I never denied phasors to be rotating vectors. You seem to have a hard time believing that does not necessarily make phasors to be equivalent to vectors.

Kosow does not exist. You can't prove he exists.

The John Wiley and Sons Publishing Company says he exists. They say he has a doctorate and is a Professor Emeritus at the College of Staten Island, City University of New York. That is prima facie evidence that he exists. Now it is up to you to prove your assertion that he does not exist.

Ratch

 

OK so phasors are vectors, whether they are rotating, doing the Pas de Deux or the Doh-si-Doh.

I take it we are talking about the red and blue arrows on the clock face in Fig 1, which I have labelled Pi for current and Pv for voltage. As seen for some arbitrary circuit containing only resistance, capacitance and inductance, the voltage leads the current by the angle between the arrows, called the phase angle.

As the arrows rotate they trace out the sinusoidal curves to the right.

So at any instant

V = Vm sin (wt)
I = Im sin (wt-p)

I am sure you know all this so am rushing through it.

The point is that both curves are sinusoidal because the length of the rotating arm is constant. I have taken the peak value, but the RMS or other may also be taken as this is only multiplication by a constant.

So the arrows form a simple phase diagram.

Every point on the voltage/time curve may be directly linked with a corresponding point on the current/time curve and the phase difference is always p.

If the length of one the arrows were not constant this would not be the case, and whilst we could directly compare the zero crossing points, we could not do so for all the values in between. The resulting time curve would not be a sine wave.

In this case it is impossible to draw a phasor diagram, since that would imply information that does not exist, between the zero crossings. So Kosow is wrong to accept non-sinusoidal waveforms alongside sinusoidal ones.

This situation arises, for instance, in a transformer core, where the voltage applied to the windings may be sinusoidal, but the magnetising current is not because of hysteresis in the core. It may be shown that the flux will be sinusoidal, however.

In Fig 2 I have plotted this out showing a typical hysteresis curve in green, linked to the voltage/current/flux v time graphs.

We construct the actual shape of the magnetising current waveformby repeatedly taking sections such as AA from the blue flux v time graph and transferring the flux across to the current v flux graph (the hysteresis curve) and reading of the current. this current is then plotted at that time.

An expanded version appears in Fig 3

So at time A, read off the flux (vertical line at A to the blue curve) and transfer across to A on the flux axis of the hysteresis curve (horizontal line)

Read current value AB (horizontal) between increasing green line and flux axis.

Plot a point B above A on the time axis to get one point on the magnetising current curve. So AB on the hysteresis graph = AB on the current/time graph.

Repeat process to obtain full current curve.

Note that the peak current ocurs at the same time as the peak flux and zero voltage, but that the curve is nowhere near sinusoidal.

This is what happen when you introduce a non linear effect into an otherwise linear system

Phasors, vectors are linear systems.

 

studiot,

OK so phasors are vectors, whether they are rotating, doing the Pas de Deux or the Doh-si-Doh.

Phasors must be rotating, or they don't exist. Phasors are derived from vectors, that is true. But let's get one thing clear. We understand each other, but do not necessarily agree that phasors are vectors. Phasors certainly have some vector-like qualities, but I am not sure they should be called vectors, for the same reason I don't like to call bread "wheat".

OK, I looked over the material you attached. Yes, the magnetizing current is nonsinusoidial. I have two observations.

1) Is there any reason why the magnitude of the phasor has to be constant? Could not the magnitude of the phasor be defined as a variable with respect to the phase?

2) Is not a nonsinusoidal wave a composite of sinusoidal waves at different frequencies and constant magnitudes? Could not a nonsinusoidal periodic wave in the duplex plane be defined as a sum of several phasors?

Let me know what you think.

Ratch

 

1) Is there any reason why the magnitude of the phasor has to be constant? Could not the magnitude of the phasor be defined as a variable with respect to the phase?

Well yes of course there is.

The whole point of a phasor diagram, that is not rivial, is to be able to add currents of voltages, or fluxes, or whatever.

This can be done using linear mathematics (phasors) if

The frequencies are the same

The rotating arm is the same.

All that differs is the phase, p.

If you think about it you are trying to add

I1 sin (w1t) + I2 sin(w2t+p)

If

w1 ≠w2

or

(corrected version)
the second term is not a sin function but some arbitrary function of time, and perhaps I2 is also not constant but a function of time so the sum becomes

I1sin(wt) + I2f(t+p)

All the linear maths worked out in post#2 does not hold true.

 

studiot,

(corrected version)
the second term is not a sin function but some arbitrary function of time, and perhaps I2 is also not constant but a function of time so the sum becomes

I1sin(wt) + I2f(t+p)

All the linear maths worked out in post#2 does not hold true.

Let's look at it from the magnitude point of view. Instead of a circle representing the constant magnitude of a phasor, we instead have a crooked loop of some shape. So the magnitude of the phasor will not be constant, but instead have a variable magnitude depending on the phase. The projection of the real and orthogonal axis will not vary sinusoidally, but they will have a particular value at each phase value. Would we not get a correct answer if we added the real parts and the orthogonal parts of two nonsinoidal voltages of the same frequency? Isn't that what we do when we add two phasors? If the result does not follow the definition you outlined in post #2, then perhaps a phasor is not a vector.

Ratch

 

How do you add an arbitrary function to a sine wave?

 

studiot,

How do you add an arbitrary function to a sine wave?

You mean a arbitrary periodic function whose values are continuous, but not sinusoidal, and repeat at the same frequency as the sine? As I said before, you can the add the real projections and orthogonal projections to get a resultant. Same as you do for two phasors.

Ratch

 

Did I say that?

Yes, you did. Just yesterday.

I never denied phasors to be rotating vectors.

Indeed. As I said. You agree with me.

The John Wiley and Sons Publishing Company says he exists.

They don't exist either.

Now it is up to you to prove your assertion that he does not exist.

What utter silliness! I don't have to prove anything!

 

thingmaker,

Yes, you did. Just yesterday.

Not at all. Just your hopeful inference.

Indeed. As I said. You agree with me.

About what?

They don't exist either.

Uh huh. And neither does my textbook, right?

What utter silliness! I don't have to prove anything!

You do if you want to be taken seriously.

Ratch

 

Not at all. Just your hopeful inference.

Nope. It's there.

About what?

About phasors being vectors. Havn't you been reading this thread? Silly Ratch!

Uh huh. And neither does my textbook, right?

You catch on quick. Only took two threads.

------------------------

You do if you want to be taken seriously.

Okay, enough of me having fun at your expense. I'll go back to it again, of course. But for right now I want to make a clear point:

http://forum.allaboutcircuits.com/showthread.php?p=115400