Short single, dual and three-phase demo. 8

[Yuma]

Unclebob, Gunnar:

I agree with Uclebob when he says that

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

And, as Gunnar says, all of this vectors turn the same direction.

When we say that for example, harmonic 5 are inverse sequence, we mean that the 5th harmonic of phase B reaches its maximum instantaneous value before the 5th harmonic of phase A.

Just draw the sine waves and see

Regards

 

[Skogsgurra]

Yes, Yuma. That is the explanation to this contradictions as it seemed to be. The phase sequance has nothing to do with if the individual harmonics rotate CW or CCW. It is about in what order the three phases cross zero in positive direction.

You can easily see that in the demo by setting fifth harmonic only and rotate the system manually with + and - keys (focus on Angle L1 box first). Then observe how L2 green component reaches positive peak before L1 does so.

Kill fifth and do the same thing with fourth. See how L1 yellow reaches positive peak before L2 yellow does. Meaning that L1 fourth comes before L2 fourth - positive sequence.

Kill forth and avtivate third. See how all three orange components always point in the same direction - i.e. they are zero sequence.

You need to think about these things. I haven't realised this until now. :-( But I am certainly glad I finally did

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]

Yuma,

It was a hell of a lot of work to draw all those sines! So, I did a simple Excel sheet to show what you just said.

And thanks to Dan Ward at Dominion Virginia Power, who sent me an Excel sheet doing "my thing". I hope that you can use the "Step 3 Procedure" to make your sheet available. I am going to try that. If it doesn't work, I will add it to our site later on.


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]

Oops!

I think that I reversed the whole thing.

Too late over here. Someone correct my mistake? Or I do it tomorrow. It is close to mid-night now.

Dan: The "step three" thing is what you do when you are posting here. See red text below Message box.

Gunnar Englund

http://www.gke.org

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

 

[magoo2]

Thanks, Skogsgurra

I looked all over the site for instructions, but never looked at the bottom of where you send your message.

I hope you enjoy the Excel piece. It doesn't do harmonics, but does a nice job with phasors.

Dan

 

[sibeen]

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.

Depends on which system you are talking about. In a 90 degrees shift, two phase system, the 3rd harmonics do add and the program shows this correctly.

In a 180 degrees, two phase system, the 3rd harmonics will cancel each other out and again the program shows this correctly. This is the equivalent of using a transformer with a centre tap which is used as the common and the top and bottom legs 180 degrees out of phase. This is quite commonly used in sites where clean power is required. Using this dual active approach gets rid of any common-mode noise between the two supplies and in this case the 3rd harmonic can be considered common mode.

Nice program, Gunnar. I wish I had it a few years ago when I was teaching in-house courses to engineers and techs who were new to the power game.

 

[Skogsgurra]

Thanks for the clarification, sibeen.

I have adjusted the excel sheet and I hope that it is correct now. Please check and leave feedback.

Gunnar Englund

http://www.gke.org

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

 

[Clyde38]

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? ...

Can you share your file or is it the same as what Mr. Englund posted?
Thanx

 

[Skogsgurra]

No, it is another one. I think that Dan/magoo2 shall do it. He "owns" it and he also knows how to do it now..

Gunnar Englund

http://www.gke.org

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

 

[magoo2]

This is the program (Excel worksheet) I sent Gunnar. I found a phasor worksheet on the web by a Professor Bruton of SFASU. He had a demo showing 2 phasors and it looked pretty neat. I think he did it for a math class.

After I looked at what he had done, I added the three phase representation and it works quite well. You need to turn off auto-calculation and make it manual. When you strike the F9 key, you'll see the 3 phasors rotate and you'll also see the voltage versus time plot.

I was just getting ready to do a short course on symmetrical components when I found this. It doesn't do harmonics, just the normal three phase phasors.

It's pretty slick - if I do say so myself. Enjoy!

 

[MAGTiger]

Kudos Gunnar! This is a cool demo, great for trying to educate the Salesman types. However, the displays seems just a couple lines too large for my screen and can't be reduced in size.

 

[Skogsgurra]

It will work better on your next 'puter. Shall have a look at that "Auto-adjust to screen resolution" feature. But lots to do right now - so no promises.

Gunnar Englund

http://www.gke.org

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

 

[DanEE]

I got the same error that the gentleman did above trying to install the software on Windows XP.. re files too old...

I was installing it on Windows 2000.

btw. I edited the setup.lst file to remove the instructions installing and registering the *.dll files and reran setup.

The program installed and runs successfully..

You need to look into the dlls you your app is trying to install vs operating system level...

Nice demo program!

http://home.4x4wire.com/deddleman/

 

[unclebob]

It works for me now, on my Windows 2000 ! Thanks to DanEE.
Here's my modified setup.lst file (see attachment)

 

[MAGTiger]

It would be great if you could show the resultant vector and then be able to turn on or off the harmonic vector displays (keep them running in background) but just show the resultant thsu to demonstrate the effect of the harmonics.