Is impedance a phasor?

[rattus]

Well, some authors treat it as such. After all, it is a complex number.

Let Z = R + jwL = 100 + j100 = 141.4 @ 45

Now apply a voltage, 120VRms @ 0, the current is,

I = V/Z = (120Vrms @ 0)/(141.4 ohms) @ 45 = 0.849A @ -45

 

[roger]

Well, some authors treat it as such. After all, it is a complex number.

Let Z = R + jwL = 100 + j100 = 141.4 @ 45

Now apply a voltage, 120VRms @ 0, the current is,

I = V/Z = (120Vrms @ 0)/(141.4 ohms) @ 45 = 0.849A @ -45

Let's just all hope that this thread will have a medium length happy life.

Roger

 

[iceworm]

Well, some authors treat it as such. After all, it is a complex number. ...

Why guess when one can look up the exact definitions. This is not philosophy.

roger -
This should be the end of it. There is no more to say.

phasor
(1) (metering) A complex number, associated with sinusoidally varying electrical quantities, such that the absolute value (modulus) of the complex number corresponds to either the peak amplitude or rms value of the quantity, and the phase (argument) to the phase angle at zero time. By extension, the term ?phasor? can also be applied to impedance and related complex quantities that are not time-dependent. (ELM) C12.1-1988

(2) A complex number expressing the magnitude and phase of a time-varying quantity. Unless otherwise specified, it is used only within the context of steady-state alternating linear systems. In polar coordinates, it can be written as Aej
, where A is the amplitude or magnitude (usually rms, but sometimes indicated as peak value) and
is the phase angle. The phase angle
should not be confused with the space angle of a vector. See also: electric field strength. (T&D/PE) 644-1994

(3) A complex equivalent of a simple sine wave quantity such that the complex modulus is the sine wave amplitude and the complex angle (in polar form) is the sine wave phase angle.

Per IEEE 100, def 1, yes, by extension, even though strictly, they are not time dependent.

By def 2 and 3, no. So that is an unequivacable Who knows.

phasor notation
For monochromatic fields, the complex notation used in the expressions for field quantities with the exponential
time factor exp{jt}. For example, for plane waves

(
r, t)
Re{
E(
r, )exp(jt)}
where

(
r, t)
the instantaneous electric field
Re indicates the real part
E
(
r, )
the phasor notation for the electric field
(AP/PROP) 211-1997

This one is good. It essentially says no.

phasor quantity
(A) A complex equivalent of a simple sinewave quantity such that the modulus of the former is the amplitude A of the latter, and the phase angle (in polar form) of the former is the phase angle of the latter.

(B) Any quantity (such as impedance) that is expressed in complex form

And another vote for no or yes.

The next two are way off topic asides

phasor power (rotating machinery)
The phasor representing the complex power. See also: asynchronous machine. (PE) [9] (2)

(A) (polyphase circuit) At the terminals of entry of a polyphase circuit into a delimited region, a phasor (or plane vector) that is equal to the (phasor) sum of the phasor powers for the individual terminals of entry when the voltages are all determined with respect to the same arbitrarily selected common reference point in the boundary surface (which may be the neutral terminal of entry). The reference direction for the currents and the reference polarity for the voltages must be the same as for instantaneous power, active power, and reactive
power. The phasor power for each terminal of entry is determined by considering each conductor and the common

(B) (single-phase two-wire circuit) At the two terminals of entry of a single-phase two-wire circuit into a delimited region, a phasor (or plane vector) of which the real component is the active power and the imaginary component is the reactive power at the same two terminals of entry. When either component of phasor power is positive, the direction of that component is in the reference direction. The phasor power S is given by S
P  jQ where P and Q are the active and reactive power, respectively. If both the voltage and current are sinusoidal, the phasor power is equal to the product of the phasor voltage and the conjugate of the phasor current.

Power is a phasor


And here is how it is calculated

phasor product (quotient)
A phasor whose amplitude is the product (quotient) of the amplitudes of the two phasors and whose phase angle is the sum (difference) of the phase angles

Fpp
cos (  )
the phasor product is
AB
|AB|ef(AB)
and the quotient is
A A
  ej(AB) B B
(Std100) 270-1966w

That last is a bit messy, but anybody that is interested surely understands. And the exact representation is in IEEE 100.

ice

 

[roger]

roger -
This should be the end of it. There is no more to say.

:lol::lol::lol:


Roger

 

[__dan]

Well, some authors treat it as such. After all, it is a complex number.Let Z = R + jwL = 100 + j100 = 141.4 @ 45 Now apply a voltage, 120VRms @ 0, the current is,I = V/Z = (120Vrms @ 0)/(141.4 ohms) @ 45 = 0.849A @ -45

You may be mixing your paradigms again.

The mathematics are an abstraction layer selected to simplify or convey simpler understanding. The math does not necessarily provide a physical mechanism of making things equal when the math indicates they are equal.

For example: E = MC^2 says all matter has an energy equivalence. Can all or any matter be converted to energy, the answer is no. If you would say yes, I have 10,000 lbs of iron on wheels in the driveway. Go ahead and convert it to energy.

Z is a fixed constant due to the circuit elements to the extent that R, L, and C are fixed in the circuit. The value of Z varies with time, but the time varying component is in the forcing function which is either the current or the voltage. I and V vary with time while Z is a fixed constant, to the extent that L and C remain fixed. Z varies with time because I and V vary with time.

The question you are asking is: does Z vary independently with time, and the answer is no, unless you have a (time varying) variable R, L, or C in the circuit.

Understanding the underlying physical reality, what varies and why, is necessary to setting up the math and knowing when GI = GO.

 

[Dennis Alwon]

These threads remind me of "The song that never ends" -- It goes on and on my friend.

 

[rattus]

Power is a phasor

ice

Sorry no, but that issue is off topic.

 

[iceworm]

You got that wrong. It's:
Sorry yes, but that issue is off topic

 

[ggunn]

These threads remind me of "The song that never ends" -- It goes on and on my friend.

The road goes on forever and the party never ends.

 

[rattus]

You got that wrong. It's:
Sorry yes, but that issue is off topic

But the general equation for p(t) has a dc offset? How can a phasor represent a dc offset?

 

[Rick Christopherson]

Please refer to the comments in the other thread you started, but impedance is a vector, not a phasor. As was pointed out, all phasors are vectors, but not all vectors are phasors. There is no rotational component in impedance, so it cannot be a phasor (well it can, but the rotation is zero and it no longer fits in the same frequency domain).

As I stated in the thread that got closed last week, the difference between a vector and a phasor is that a phasor contains a suppressed rotational component. Phasor = rotating-vector = phasor. By suppressing the rotating component of a vector and giving it the new name "phasor" we can then intermingle the two for performing analysis.

 

[iceworm]

Caution - off topic comment to follow.

You got that wrong. It's:
Sorry yes, but that issue is off topic

But the general equation for p(t) has a dc offset? How can a phasor represent a dc offset?

This is not philosophical. It is an IEEE 100 definition. You should really read it.

ice

 

[iceworm]

Please refer to the comments in the other thread you started, but impedance is a vector, not a phasor. As was pointed out, all phasors are vectors, but not all vectors are phasors. There is no rotational component in impedance, so it cannot be a phasor (well it can, but the rotation is zero and it no longer fits in the same frequency domain).

As I stated in the thread that got closed last week, the difference between a vector and a phasor is that a phasor contains a suppressed rotational component. Phasor = rotating-vector = phasor. By suppressing the rotating component of a vector and giving it the new name "phasor" we can then intermingle the two for performing analysis.

According to IEEE100, "phasor(1)(metering): Impedance can be considered a phasor.

Rick - you are pretty sharp. But I'll take the IEEE 100 definition over yours most days - okay any dy.

ice

 

[Rick Christopherson]

According to IEEE100, "phasor(1)(metering): Impedance can be considered a phasor.

Rick - you are pretty sharp. But I'll take the IEEE 100 definition over yours most days - okay any dy.

ice

You're welcome to take that approach, but that is the equivalent to reading CliffsNotes for a Shakespeare play. IEEE did not invent the concept of phasors. It is a math concept that is far broader than IEEE. I don't read Shakespeare, but if I did, I wouldn't base my knowledge on a CliffsNote.

BTW, the word "considered" doesn't contradict what I said.

 

[iceworm]

According to IEEE100, "phasor(1)(metering): Impedance can be considered a phasor.

Rick - you are pretty sharp. But I'll take the IEEE 100 definition over yours most days - okay any dy.

ice

You're welcome to take that approach, but that is the equivalent to reading CliffsNotes for a Shakespeare play. IEEE did not invent the concept of phasors. It is a math concept that is far broader than IEEE. I don't read Shakespeare, but if I did, I wouldn't base my knowledge on a CliffsNote.

BTW, the word "considered" doesn't contradict what I said.

Rick -
That doesn't make any since at all. Phasor is a word - that's all, just a word. It is a collection of letters. It needs a definition if it is to be used in communication. IEEE 100 provides definitions that are agreed upon by most authorities. IEEE not inventing the concept of phasors has no bearing on validity of the definition.

You want to redefine "phasor" to something other than the IEEE 100 definition - that's okay with me. But you should not count on anyone understanding what you mean when you make up your own definitions.

ice

 

[iceworm]

This post is for the group of casual readers that stop by for an occasional chuckle at the elite. The elite are requested not to respond:
This previous post on IEEE definitions does not include words used in casual technical conversation where ithe intent is apparent through the context. For example, I know what you mean when you say, "split-phase" or "Single phase".

Additionally, Why would anyone cares if the arrows point the same direction or opposite directions? It's just a math model. It works either way. The problems solve equally well.

We have done all we can here , Tonto. It's time for us to go.

He Who Knows

 

[rattus]

Why guess when one can look up the exact definitions. This is not philosophy.

roger -
This should be the end of it. There is no more to say.


Per IEEE 100, def 1, yes, by extension, even though strictly, they are not time dependent.

By def 2 and 3, no. So that is an unequivacable Who knows.



This one is good. It essentially says no.



And another vote for no or yes.

The next two are way off topic asides



Power is a phasor


And here is how it is calculated

That last is a bit messy, but anybody that is interested surely understands. And the exact representation is in IEEE 100.

ice

Don't have IEEE 100 and your excerpt from it came through all garbled. Whatever I think our discussion should be limited to steady state analysis of AC circuits, and I repeat, there is no way to describe a dc offset with a phasor because it does not have a phase angle. We are in the wrong thread anyway.

 

[Rick Christopherson]

Rick -
That doesn't make any since at all. Phasor is a word - that's all, just a word. It is a collection of letters. It needs a definition if it is to be used in communication. IEEE 100 provides definitions that are agreed upon by most authorities. IEEE not inventing the concept of phasors has no bearing on validity of the definition.

You want to redefine "phasor" to something other than the IEEE 100 definition - that's okay with me. But you should not count on anyone understanding what you mean when you make up your own definitions.

ice

It is defined. It is defined in the broader field of Mathematics.

Here's an analogy: If someone came forward and publicly stated that the NEC was a great instruction manual for a DIY'er to rope a house, how many of our members would be scrambling to their trucks to fabricate their best Romex noose?
:jawdrop:

IEEE is no different. It is a reference to remind us of our education....not intended to supplant our education. It's a subset of what we should already know from our education.

The IEEE definition is a subset to the full mathematical definition. Just as the NEC is a subset to to the more complex methods we could use for defining safe wire size and thermal transfers.

What you should note, is that what I stated is not contradicted by your IEEE reference. You misread your IEEE reference to say one thing, but it actually makes a broader statement that agrees with what i stated. These published documents don't use words willy-nilly. Care must be taken when reading them.

 

[iceworm]

... Here's an analogy: ... how many of our members would be scrambling to their trucks to fabricate their best Romex noose. ...

rick -
I have a suggestion. Leave out the metaphores, analogies, similies, other non-sequiturs. Shakesphere really doesn;'t have muchto do withthis

... You misread your IEEE reference to say one thing, but it actually makes a broader statement that agrees with what i stated. ...

So I mis-read it and it actually agrees with you. uh-hu :huh:

...IEEE is no different. It is a reference to remind us of our education....not intended to supplant our education. It's a subset of what we should already know from our education. ....

So IEEE only counts when it is convenient to your argument. okay :blink:

Rick - your arguments are pretty ludicrous. I'm not comfortable continuing this.

... These published documents don't use words willy-nilly. Care must be taken when reading them.

However, I agree with this statement.

ice

 

[Rick Christopherson]

Nothing in my previous posting, or postings throughout this thread, warrants the antagonism and animosity that you are displaying with your latest response. Although the subtlety of your comments doesn't break any rules, and to the casual observer (or moderator), they seem meaningless; to active participants, they are antagonistic. That eventually leads to comments in-kind, and then this all escalates until the thread closes.

I am open to carrying on a debate, but not under these terms.