Is power a phasor or vector or neither?

[rattus]

from MathWorld: Phasor is the representation, "beloved of engineers" and physicists, of a complex number in terms of a complex exponential
in other words, every complex number can be represented in "Phasor" form, i.e., Phasor ≡ Complex number ≡ 2-D vector

P: real power, real number
Q: reactive power, real number
S: apparent power, complex number or phasor

S = P +jQ

http://mathworld.wolfram.com/Phasor.html

I am always right.

I must disagree with Mathworld. A phasor is a complex number with a magnitude and phase angle.

We can treat vectors as complex numbers, but they carry a direction in space rather than a phase angle. That is the difference between phasors and vectors.

Yeah, I made a mistake once. Thought I was wrong.

 

[iceworm]

P: real power, real number
Q: reactive power, real number
S: apparent power, complex number or phasor

S = P +jQ ...

George -
I know you already know/understand all of this - so I'm just discussing my own failings in understanding the complexities of the model. None of this is pointed at increasing your understanding. It is just my philosophical addition to the thread.

I always have liked (and this is a "like" not a "have to have"):

1. "apparent power" as directionless, a scalar, the number that is porportional to the generator stator heating

2. "S" is the complex power. a phasor (or vector if one likes), has direction, a phase angle.

3. "jQ" is reactive power. For vars toward the load, the load is inductive, the vars are plotted up the page, that why Complex Power is defined as E(I*). It is the number that sets the DC drive to the field. The number that sets the field heating. The number that sets the flux between the field and stator.

4. P, real power, is the throttle setting, the driver shaft output, cause that is the only place the power can come from.

Just rambling. Yes I know there are other factors that influnce the above and there are a bunch of nuiances I left out.

I am much more interested in turning on the lights than I am in the pure math. As an example, Maxwell was a mathematician, he didn't build much of anything. Faraday's math skills pretty well sucked (compared to Maxwell), however, he built a generator. Yes, this is a simplistic generalization.

The math models are only useful to me as far as they can accurately model the physical process. To paraphrase charlie b: We are not talking about power, that is a physical thing. We are talking about a math model of the physical behavior. (Appologies to charlie b for mangling his post)

ice

 

[iceworm]

I must disagree with Mathworld. A phasor is a complex number with a magnitude and phase angle.

We can treat vectors as complex numbers, but they carry a direction in space rather than a phase angle. That is the difference between phasors and vectors. ...

And that's it? There is no other difference?

ice (seeking enlightenment in the way of the phasor - and that's the truth, I am)

(edit to add question marks - these are questions)

 

[iceworm]

A few notes on the OP:
Disclaimer: The following are personal opinion, generalizations/philosophy - not to be construed as absolute truth:

Is power a phasor or vector or neither?

I say neither because the expression for real instantaneous power involves a dc offset modulated by a sinusoid of frequency 2wt. ...

I will say neither as well, but for a different reason;
Power is hammering diesels, whining turbos, screaming turbines, burning paint, live conductors that will kill you, burn your DNA beyond recognition. Complex power, phasors, vector representations, those are just squiggles on paper - parts of math models.

... Some think that the power triangle proves that power is a vector, but here we simply use complex numbers to represent real and imaginary power. ...

That is what all math models are used for - to represent physical process. Some think that is the important part - the math model does not exist to glorify the pure math.

... Also, the power triangle always falls in the first quadrant. ...

Not if one considers Complex power. That can fall in any one of the quadrants - although generally in first and fourth. Generally, if a generator is operating in the second or third quadrants, it is within milliseconds of a trip.

ice.

 

[mivey]

Is a phasor or vector a concept or an obsession?

Given that choice, it must be a concept because Obsession is the new scented tool line from Kalvin Klein. A discerning fragrance for the discerning working man.

 

[mivey]

Is power a phasor or vector or neither?

Neither. Who said otherwise (to spawn the thread)?

 

[LMAO]

George -
I know you already know/understand all of this - so I'm just discussing my own failings in understanding the complexities of the model. None of this is pointed at increasing your understanding. It is just my philosophical addition to the thread.

I always have liked (and this is a "like" not a "have to have"):

1. "apparent power" as directionless, a scalar, the number that is porportional to the generator stator heating

2. "S" is the complex power. a phasor (or vector if one likes), has direction, a phase angle.

3. "jQ" is reactive power. For vars toward the load, the load is inductive, the vars are plotted up the page, that why Complex Power is defined as E(I*). It is the number that sets the DC drive to the field. The number that sets the field heating. The number that sets the flux between the field and stator.

4. P, real power, is the throttle setting, the driver shaft output, cause that is the only place the power can come from.

Just rambling. Yes I know there are other factors that influnce the above and there are a bunch of nuiances I left out.

I am much more interested in turning on the lights than I am in the pure math. As an example, Maxwell was a mathematician, he didn't build much of anything. Faraday's math skills pretty well sucked (compared to Maxwell), however, he built a generator. Yes, this is a simplistic generalization.

The math models are only useful to me as far as they can accurately model the physical process. To paraphrase charlie b: We are not talking about power, that is a physical thing. We are talking about a math model of the physical behavior. (Appologies to charlie b for mangling his post)

ice

just one thing: 'Q' is the reactive power not 'jQ'.
S (apparent power) = P (real power) + jQ(reactive power).

And again, S is a complex number and "can" be represented in |S|e^jϕ where ϕ is the phase angle.

Complex number ≡ 2-D vector ≡ Phasor

 

[iceworm]

just one thing: 'Q' is the reactive power not 'jQ'. ...

Yeah, I thought about that. However, "jQ" gives it a direction (on the sheet of paper - not space) and just "Q" really doesn't. And most times one is doing a calculation, it's with jQ, not just Q.

But, in either case, that's in the "If you like it that way - I don't mind a bit." arena.

ice

 

[pfalcon]

Just as a square is a special case of a rectangle; the phasor is a special case of the vector. Anything that can be done with a phasor - is being done with a polar vector.

Phasors are the polar coordinate form of a vector. Polar coordinates being much easier to use with frequency response. "Static" phasors are used when frequencies are identical because the frequency part cancels throughout. The frequency portion being the "rotating" part of the phasor.

By mathematical definition the product of two vectors is a vector.

 

[ggunn]

But what is right?

Where is the reference point?

If I am negative left does that make me right?

Two wrongs do not make a right, but three rights make a left.

 

[pfalcon]

Just as a square is a special case of a rectangle; the phasor is a special case of the vector. Anything that can be done with a phasor - is being done with a polar vector.

Phasors are the polar coordinate form of a vector. Polar coordinates being much easier to use with frequency response. "Static" phasors are used when frequencies are identical because the frequency part cancels throughout. The frequency portion being the "rotating" part of the phasor.

By mathematical definition the product of two vectors is a vector.

I was prompted to clarify something.

The CROSS product results in the usable vectors. The DOT product is a projection of one vector onto another vector discarding direction for its purpose, therefore a scalar result.