Phasor Diagrams

For the vector part try:

Phasors are graphical representations of complex numbers. Although they have some properties of vectors, addition for example, THEY ARE NOT VECTORS. This shows up when multiplying phasors to determine power. Although there is real and reactive power, power is not a phasor. That is, phasors are good for representing amplitudes--not intensities.

Advice: Learn the algebra of complex numbers backwards and forwards. Use phasor diagrams for visualization and understanding. Phasors are good for visualizing modulation, both amplitude and frequency modulation. In particular, remember that on the diagram, you are rotating with the phasor so that it looks as if it is still.

Bill

-- Fermez le Bush

I think you are wrong. In pure math, phasors are a form of vectors.

Phasors can tell you if the power factor is leading or lagging, if the current is lagging the power factor is lagging. Phasor diagrams are nice because they can show you all the angles and magnitudes of all parameters. Grab a electrical engineering book and read about transformers, there equivilent circuits and phasor diagrams.

Power factor is important, by looking at the phasor diagram and seeing where the current is with respect to the voltage you can tell if some machine are a motor or generator.

Say P.F. = 08 lagging

Since P.F. = cos theda

Theda = cos-1 P.F.

Theda is the angle between your voltage and current.

Whats Theda ? do you mean Theta ?

Please explain what you mean by "pure math."If you think that phasors are vectors, explain what the dot and cross products are for two phasors.

Phasors are representations of complex numbers in two dimensions. It so happens that, because of commutativity and associativity of complex numbers, their phasor representation allows sums of two complex numbers to be represented by the vector sums of phasors. That property by itself does not make a vector out of a phasor. In fact, the term phasor is used instead of vector to emphasize that distinction.

-- Fermez le Bush

Search Google with "are phasors vectors"

I got 98,300 results.

Some higher learning pages where they show a relationship between vectors and phasors are:

I do not need to rely upon anything anyone else says. I understand vectors. I understand phasors. I understand tensors. I understand pseudovectors such as the Poynting vector. A pseudovector is a cross product of two vectors which is disguised as a vector while it really is an antisymmetric tensor with zero for its diagonal elements.

What would Googling add to my knowledge?

Bill

-- Fermez le Bush

You said phasors are not vectors. Your statement is not supported by many in the community. Perhaps, you are not open to new ideas, but that doesn't mean others are always incorrect. The literature shows that phasors are a form of vectors.

Phasors share some properties with vectors. That does not turn a phasor into a vector. Transcendental numbers can be added and subtracted. Integers can also be added and subtracted. That does not mean that a transcendental number, like pi, is an integer. There is a formal name for the kind of fallacy you have fallen into, but I do not remember what that name is.

Note that many items found on the internet are flat out wrong. The nice thing about mathematics is that if you do not make a mistake in reasoning, you will be correct no matter what anyone else says. That presumes that the postulates for any such branch of mathematics is self consistent.

R. P, Feynman wrote (with help) a book entitled "What do your care what other people think." While I am no Feynman, I am close enough when it comes to phasors.

Bill

-- Fermez le Bush

The dot product actually makes sense for some phasors, take the voltage, current, angle between them and you get the power when you use the dot product.

You could do the cross product too, but i'm not sure what good that does and probably has no physical meaning yet.

I was alway told, that a vector has a magnitude and direction (i'm sure this is as dumb as it gets, but you have to start somewhere), phasors have this qualitly.

But I'm not saying a phasor is a vector, and i'm not saying its not a vector.

Now that I think about it, the cross product for two phasors must has some meaning, Maxwell's equations uses the cross product to decribe electro-magnetic waves. I bet if you really thought about it would be usuful in some application. Maybe it gives the direction of the magnetic flux in the transmission line. Maybe not!

My definition of a phasor diagram is: "A phasor diagram is composed of a number vectors, and there position with respect to each other." I'm not even sure a phasor is a word without the word diagram after it.

A phasor is a two dimensional representation of a complex number. That is it. It is not the equivalent of a vector in three or more dimensions. It is true that the scalar product of two phasors as calculated from their dot (scalar) product has meaning.

It is also true that a cross product of two vectors has meaning such as in a Poynting vector. But a Poynting vector is NOT a vector. If the three dimensional coordinates x, y, and z get inverted, The electric and magnetic fields change sign. The Poynting vector does not get inverted. That means that a cross product is not a true vector because it does not transform the way a vector does. That entity is called a pseudovector and transforms like an antisymmetric tensor.

Many engineers use tensors without knowing it. They use subterfuges such as Mohr's circle for calculating combinations of shear and tensile stress. Another poor man's approach to two-dimensional tensors is to use dyadics.

Bill

-- Fermez le Bush