xd and xq

I mean especially for synchronous generators.

A connecting principle, Linked to the invisible Almost imperceptible Something inexpressible. Science insusceptible Logic so inflexible Causally connectible Yet nothing is invincible. If we share this nightmare Then we can dream Spiritus mundi. If you act, as you think, The missing link, Synchronicity.

Simply,,uh,,no....

http://yourelectrichome.blogspot.com/2012/04/direct-and-quadrature-axis-synchronous.html

Sure, it's a great interview question because most handbook and wannabe power engineers only respond with a blank stare, and the benefit to society is enormous as they get weeded out.

That aside, I guess that you didn't know that Xd and Xq are nearly the same for round rotor synchronous machine therefore seeing two different values tells you it's a salient pole machine.

The most important use is calculating how a machine behaves under steady state conditions, most handbook engineers recognize the machine's reactance as plain old X, when in fact it's Xd or (Xd+Xq)/2.

btw- how about some response from you on your recent inane "harmonics metering" post?

Hey dude, I think you are always guessing wrong, I am not totally ignorant of these concepts, I had learned what you say boasting when I was in college , By the way , the average value you gave is a negative sequence not X value...

On the other side, You called what I said inane, but I think the answer you gave in the first occasion was "inane". Who are you ? Some guy who just read through the basic sites online and selling the information crumples here? I think to be guru must be much more special than yours case..

I asked the harmonics measurement questions before examining the sources. I made some searches but I think they did not satisfy my soul. I guess harmonics do not effect current transformers up to a frequency, but the gist lies in the measurement, So I expect some "decent" people give a good answer for this question (magnetic core " power" measurements of harmonics-inflicted power systems ).

Hey ramconsult please do not try to help people whose questions you consider inane!

In engineering there is no guessing about basic concepts. If, as you say, you learned about machine reactances then you would already know their importance, so why ask the question, especially in such a superfluous manner? Oh, and you would also know that X2 = (X"d+X"q)/2 for round rotor machines.

The only "guessing" that I do is to understand what motivates the question. For the most part I use the information as presented in the original posting and try and "fill in the blanks" when certain pertinent information is missing or mis-stated.

Actually your CT question was a good one, I thought that you were going to make the argument that the frequency response of the meter wouldn't allow it to accurately display the current of the higher harmonics. I twitted you because you usually respond to requests for more info but had no comment in this case and I wanted to continue the thread to see where you were going to take it. My bad, Dude.

I think you can try to name the questions you admire as "good" rather than name them "inane".

By the way ,Rixter had given an answer but I think to measure power and current is different in this case. Admittedly I am not sure. Also it can be said are commonly used conventional measurement devices are electrodynamic type? I ask this question since there are many many types of measurement devices of conventional magnetic core type...

Almost all analog movements are of the electrodynamic type, also know as a galvanometer. The thing that distinguishes them from each other is usually the internal circuitry between the circuit being sensed and the meter movement itself.

In the specialized case of measuring a nonsinusoidal waveform full of harmonics a thermo-galvanometer can be used. The front end circuitry is a resistive element that is heated by the current passing through it, the temperature of which is sensed by a thermocouple whose output is attached to the galvanometer. Since power = I²R the temperature of the resistive element is proportional to the power being dissipated.

A similar device known as a hot wire ammeter operates on the same sensing principle, but instead of a galvanometer movement the pointer is mechanically coupled to the sensing wire and deflects in proportional to the change in length of the element as it expands or contracts in response to the heating from the current passing through it.

Most of these beasts can only be found in technical museums. They have been replaced by modern digital meters that use DSP techniques to do a Fast Fourier Transform on the waveform as it is digitized and then use data to calculate the power spectra in specialized μprocessor chips.

Thank you for your trying to be helpful, I had thought, you would not give a proper answer after our last conversations..

Anyway , this is really kind of you ...

I enjoyed your post...

Also a good rating..

if the flux passing thru direct axis faces a less reluctance compared to q one, so why is reactance of d axis is larger than q in salient pole machines?

Because the flux distribution is nearly sinusoidal in the d-axis due to the nearly uniform air gap across the pole face, while in the q-axis the flux distribution is highly distorted due to the space between the poles. Since these are lumped, not distributed, parameter models, compromises were often made to accommodate what was measured in the machine versus the theoretical calculations.

The underlying theory including detailed vector diagrams can be found on pages 148-149 in the Westinghouse T&D Reference Book, or in any good AC Machines textbook. As is noted on page 149, "...fortunately there is not as much need for this quantity (Xq as there is for Xd)..."

Class dismissed.

so why is this inversely related? İf there is a smoother flux in the d axis , then is it not normal that there should be a less reactance?

okay , I finally found it:

1

"In a salient-pole machine, xaq, the cross- or quadrature-axis reactance is smaller than xad, the direct-axis reactance, since the flux produced by a given current component in that axis is smaller as the reluctance of the magnetic path consists mostly of the interpolar spaces."

2

combining these two --------> the ability of a unit current to form a flux is related to the inductance positively, so inductance leads us to REACTANCE!

Happy to me...

Amazing what can happen when we ferret these things out for ourselves...