Short single, dual and three-phase demo. 8

[Skogsgurra]

Hello! I have been giving short seminars on diverse topics in electric drives for many years. And one thing that seems to be very difficult for many people is why the standard mains voltage is sine formed. And also what a three phase system really is. Not to mention two-phase systems.

Add to that what harmonics are and their relation to the fundamental. So we made a short and simple demo program to show what is going on. I hope it is self-explaining. If not, I will add some instructions here.

Go to

http://www.gke.org/test/

download, unzip and run the install wizard.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[itsmoked]

Wow. Pretty spacey vectors. Especially 3-phase with all harmonics even, and odd.

I wish you had more solid (wider) vectors that carried the color over to the graph so it was easier to tell which vector is causing what waveform.

Unfortunately I suspect this is not going to help much in the student realm. Just my guess, but I believe more questions may be raised than answered.

Be interested to hear what you find in the classroom.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

Right you are, Smoked!

It is intended to raise questions. And then I can use the system to answer those questions.

Like this one: How do even harmonics sum in a three-phase system. Easy to demonstrate - just run a three-phase system add even or non-triplene harmonics. Click "Show Sum" to see where the sum (the black dot) is and also see what happens to the neutral wave-shape.

Then do same thing with a two-phase 90 degrees system. Surprise! At least it was for me.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[Skogsgurra]

A short "Get started" for the demo:

Before you run, you should go to “Phase Configuration” under “Harmonics” and select “Single phase”. That is so that you do not get confused by several vectors.

You should also deselect all boxes under “Show harmonics” so that you do not get lots of harmonics to disturb you.

You may have to click the “Clear Graph” button under “Animation” and perhaps also “Run/Stop”. The box “Angle L1” shows the actual angle (L1 means phase 1 in the grid) from starting position. The angle is reset after 360 degrees. You can enter any angle in that box to get a new vector angle. You can also use the + and – keys to rotate the vector. Just experiment away!

When you feel like you want to know what a three-phase system looks like, you can go to “Phase Configuration” under “Harmonics” and select “Three phase”. There are also two two-phase options. The 90 degree option is what Tesla used for his first induction motors. The second system is sometimes still used in rural distribution – and also by some railway companies.

You can add harmonics to your liking. Just check the boxes and see what happens. The amplitudes of the harmonics are inversely proportional to their numbers. That is, third is 1/3rd and eight is 1/8th and so on.

The “triplenes” are interesting. They are always in-phase (pointing in same direction) with each other. That means that they do not cancel when added. They work together to produce a current if a load is connected between phases and neutral. Checking the box “Show sum” produces a black dot that shows the sum of all three voltages. As you can see, the sum of three phases without any harmonics is zero – the dot is staying in center of the system. If you add harmonics, you will see how the dot (the sum) starts moving around. One special case is when you have only the third harmonic activated. You will then see how the sum moves around a lot and that the projected wave-form to the right has a component that has thrice the frequency of the fundamental. This is what heats the neutral if you have lots of (third harmonic) distortion in your system. Ninth does the same thing. And so does sixth, but you should never have much of that. Even harmonics are not only unusual, they are also harmful.

There is audio as well! Not “to scale”. A 50 or 60 Hz hum isn’t heard very well through the PC speaker, so Lars took the frequencies up a bit so you can hear what happens when harmonics are added. Press “Play” under “Sound of L1” to listen. There will be a few seconds of silence while the program generates the wav file, which is then played through the speaker. Adding more harmonics produces a “richer” tone.


Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[slavag]

Hi Gunnar.
Thanks a lot.
It's intresting.
Best Regards.
Slava

 

[rtronics]

WARNING - DON'T try running this program on a WIN98se system.

It substitutes a nonrunning Oleaut32.dll in the windows\system folder.

This causes whole chunks of the OS to not load on startup.

Guess how I just found this out.

Regards, Ray.

 

[Skogsgurra]

Thanks for the catch, Ray!

Sorry about that. Where is 98se used? Anything one can do about it?

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[Skogsgurra]

Hello again!

Thanks for the PLSes. I shouldn't have them, really, but our programmer Lars. I will transfer them to his pay account - with due reduction of number of SEKs, of course.

I am a bit concerned about that problem with WIN98se. We have run the program on four different computers with different OSes. From Win2000 via XP to Vista. I know that the Millennium was a trouble-maker, but have never seen the 98se and do not know anything it. Input most welcome! Anyone?

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[itsmoked]

se was an upgrade from straight 98. Probably most people who still cling to 98 are running se.

If you will notice rtronics stated which file was the issue. Notice the '32'? 98 was not a 32 bit OS if I remember correctly. So as soon as your program landed a 32 DLL in his system he was bound to have an issue,<screwed>.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[flexoprinting]

Hello Skogsgurra

I had no trouble with the program and thanks BTW for it I am finding it interesting, also watching for input and questions from others.

For the people having trouble with the older operating systems I would think they could run it in compatibility mode, this is a feature specifically for these conditions.

 

[itsmoked]

Except compatibility modes are for backwards compatibility. If Skoggs program uses a 32bit program and 98se doesn't understand 32bit programs a compatibly mode probably won't help.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[flexoprinting]

Ah yes, correct you are. Like they say "My bad!"

 

[magoo2]

Skogsgurra,

I've got a similar demo that is all in Excel. How do I upload it so I can share it with you and others?

 

[unclebob]

Nice... but I have one hell of a question:

In a balanced 3-phase system, the fondamental, 7ht, 13th...
are direct sequence and are turning counter-clockwise.

Should'nt the 5th, 11th, ... be turning clockwise?

Am I mixing things?

 

[Clyde38]

Hi Magoo,
Go to step 3 of the post and attach.

 

[dpc]

So for some reason, I can't install this on my XP system. When I run the installer, I get an error message saying the system files are too old and that it will update the system files, but then I need to restart my computer and re-run the installer. After doing this twice, I get the same error.

I must be missing a step?

Dave

 

[Skogsgurra]

unclebob,

This is exactly one of those questions that this demo rises.

The harmonics as such all turn in the same direction and that means that the rotation speed is proportional to the frequency. So, the demo is correct. The positive direction has been chosen for the whole system and that means that all vectors rotate in the same direction. The fact that the projected wave-form is what one would expect from the given mix of harmonics is also, I think, an indication that the demo does the right thing.

The statement that some components are zero-sequence, some are positive and some are negative sequence pertains to a distorted system decomposed into symmetric components. I am not so sure that one can translate that directly to this demo.

But, I would love to have someone's view on this. I have asked myself quite a few questions in the same direction when I have tried different set-ups. Especially the role of triplenes in a two-phase system. In such a system, they do not add. Contrary to my belief.

David,
I had the same problem until Lars told me to unzip all files and then run the install wizard. Must be someone out there that can put that into a step-by-step instruction.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[unclebob]

Was reading about harmonics in ubalanced systems. In unbalanced systems, symetrical components are applied on the fondamental to describe direct, inverse and zero-sequence. When adding harmonics, symetrical components are applied to each and every harmonic, thus decomposing them in direct, inverse and zero-sequence components.

Symetrical components is a powerful tool...

 

[unclebob]

Sorry, my previous post was incomplete.

If and only if the system is balanced, then it is true that:

Harmonics 1, 4, 7,... are direct sequence;
Harmonics 2, 5, 8,... are inverse sequence and
harmonics 3, 6, 9,... are zero sequence.

Isn't that amazing!!!

 

[dpc]

Gunnar,

Yes, that what I did and I just did again - still getting the same error message after rebooting. Must be a conflict with some other program.

Dave