May I ask a question about the single vs two phase stuff

[Besoeker]

That most guys will never touch a scope or such. Sine waves are something they just kinda understand in a vague and abstract way at best.

The pics are just simple illustrations to show simple points to simple people.

Trust me they serve a purpose at a certain level for field purposes.

Wouldn't they serve that purpose if they were shown correctly?
Or any purpose at all if all they have is a vague and abstract understanding of the matter?

I think we are done here.

 

[jumper]

Wouldn't they serve that purpose if they were shown correctly?
Or any purpose at all if all they have is a vague and abstract understanding of the matter?

I think we are done here.

Bes, I am not saying by any means that they were correct.

They are not my pics, I just snagged them to illustrate.

The pics work in the field for showing a graphical representation of what the newbies can measure with a meter. They see Vrms readings with meter and the pics depict that in context.

I explain that to them as I draw it out.

 

[Besoeker]

Bes, I am not saying by any means that they were correct.

They are not my pics, I just snagged them to illustrate.

The pics work in the field for showing a graphical representation of what the newbies can measure with a meter. They see Vrms readings with meter and the pics depict that in context.

I explain that to them as I draw it out.

I hope I didn't come across as rude. I just expressed my views on the matter and there is not a lot else for me to add that would be any more constructive.
I'll go back to beating my son at chess.................

 

[jumper]

I hope I didn't come across as rude. I just expressed my views on the matter and there is not a lot else for me to add that would be any more constructive.
I'll go back to beating my son at chess.................

Not rude at all, sometimes I have to teach at a very basic level, analogies and illustrations, like these and the beer foam for VARS, a hose and water for simple V=IxR, Larry’s batterys sim, and such have a place.

Obviously not in the classroom, but in the field for newbies...Yes IMO.

I was classically trained like others, so yes they are silly and yes, false, but I see no harm in them in a simple basic level.

Do not fall into a Queens Gambit opening unless you truly do not need her. I play chess also.

 

[Besoeker]

Not rude at all, sometimes I have to teach at a very basic level, analogies and illustrations, like these and the beer foam for VARS, a hose and water for simple V=IxR, Larry’s batterys sim, and such have a place.

Obviously not in the classroom, but in the field for newbies...Yes IMO.

I was classically trained like others, so yes they are silly and yes, false, but I see no harm in them in a simple basic level.

Do not fall into a Queens Gambit opening unless you truly do not need her. I play chess also.

Thank you sir Jumper. And I'm sure you are right. I know I am a pedant on some matters. here and elsewhere.

But I have a lovely dog.

 

[jaggedben]

...

Now someone made a comment about there not actually being any "time shift" with three phase. I'm picturing a rotating generator shaft and having a little problem with that comment. Might be a chance for me to learn something more out of this thread.

I think that was me. I'll try to make the point with pictures instead of words. (Please pardon quick, crude editing of the Wikipedia image.)

If something momentarily disrupts the generator shaft rotation, the resulting voltage dips would be better represented by a graph like this...


...than by a graph like this.


The point is possibly even more more true when we're considering a 120/240 transformer with single phase primary.

 

[jaggedben]

...

With that in mind let me ask the following. Say you have a complex, non-periodic waveform. Yet say over a half cycle it might be close to periodic. Now if we break it down with Fourier transformation to individual sine waves, and phase shift them by 180 degrees, and then sum them back together......well are we back to 180 = -1?
...

I've been trying to make this point since post 241.

If the half-cycles are symmetric, then 180deg = -1.

If they are not symmetric, then -1 works better.

 

[jaggedben]

...

You really feel 50% have no idea what root, mean, square is? That is sad if it is true.

I'd guess more like 99%.

 

[Carultch]

I think that was me. I'll try to make the point with pictures instead of words. (Please pardon quick, crude editing of the Wikipedia image.)

If something momentarily disrupts the generator shaft rotation, the resulting voltage dips would be better represented by a graph like this...
View attachment 21015

...than by a graph like this.
View attachment 21016

The point is possibly even more more true when we're considering a 120/240 transformer with single phase primary.

And you would be correct. The disturbance would happen to all three phases simultaneously, rather than delayed by 1/3 of a cycle each.

The cause of the three phases being separated by 1/3 of a cycle each in the first place, has to do with the magnets or coils (whichever is on the rotor) being placed around the circle at 120 actual degrees apart (actual as in you can measure them with a protractor in the real world). This causes the cycle of magnetic field strength within the coil to each reach its peak values at 1/3 of a rotation period apart. One might have peak north magnetization, while the other two have 1/2 as much magnetic field strength in the south direction. One of the other two is increasing in south-directed strength, the other is decreasing in its south-directed strength, soon to reverse and have north-directed field strength.

So a disturbance disrupts the cycle at the time the disturbance happens. The disruption of a 3-phase doesn't delay on the 2 remaining phases, after the rotation has resumed normal operation.

Here is an animated diagram that shows it well. This one happens to use two coils for each phase on opposite ends. The principle is the same as if there were only 3 coils spaced 120 degrees, instead of six coils spaced 60 degrees.
https://i.imgur.com/lIACOng.gif

 

[jaggedben]

And you would be correct. The disturbance would happen to all three phases simultaneously, rather than delayed by 1/3 of a cycle each.

The cause of the three phases being separated by 1/3 of a cycle each in the first place, has to do with the magnets or coils (whichever is on the rotor) being placed around the circle at 120 actual degrees apart (actual as in you can measure them with a protractor in the real world). This causes the cycle of magnetic field strength within the coil to each reach its peak values at 1/3 of a rotation period apart. One might have peak north magnetization, while the other two have 1/2 as much magnetic field strength in the south direction. One of the other two is increasing in south-directed strength, the other is decreasing in its south-directed strength, soon to reverse and have north-directed field strength.

So a disturbance disrupts the cycle at the time the disturbance happens. The disruption of a 3-phase doesn't delay on the 2 remaining phases, after the rotation has resumed normal operation.

It occurs to me that if one of the components had a defect, then perhaps one would see a graph somewhat resembling my second one. However, the same definitely cannot be said of a 120/240 service with a single phase primary.

 

[jumper]

I'd guess more like 99%.

I was trying to be polite...

 

[jumper]

Thank you sir Jumper. And I'm sure you are right. I know I am a pedant on some matters. here and elsewhere.

But I have a lovely dog.

By all means I am quite pedantic also, trust me.

I would never presume to post such pics beyond a “simple” lesson to a noobie.

Gads, Bes, my professors would kill me.

I miss my dog.

 

[LarryFine]

I'd guess more like 99%.

I'm apparently in the 1% then; I've known what RMS means for, well, decades.

 

[ActionDave]

I'm apparently in the 1% then; I've known what RMS means for, well, decades.

I'm in the 99% that knows about it but doesn't care, even a tiny bit, because it has no effect on my life.

 

[Besoeker]

By all means I am quite pedantic also, trust me.

I would never presume to post such pics beyond a “simple” lesson to a noobie.

Gads, Bes, my professors would kill me.

I miss my dog.

Somewhat related......
I was at a transformer manufacturer's works in Birmingham (UK Midlands) for a witness test.
The chief tester had a poster with a big fearsome guy behind a desk with his title.
"President of the Pedantic Society".
A little guy had approached the desk.
"Sir, shouldn't that be "President of the Society of Pedants?"

What dog did you have?
Ours is a collie.

 

[jumper]

Somewhat related......
I was at a transformer manufacturer's works in Birmingham (UK Midlands) for a witness test.
The chief tester had a poster with a big fearsome guy behind a desk with his title.
"President of the Pedantic Society".
A little guy had approached the desk.
"Sir, shouldn't that be "President of the Society of Pedants?"

What dog did you have?
Ours is a collie.

Wired haired fox terrier, my avatar is him, jumper was his name.

 

[jumper]

I'm in the 99% that knows about it but doesn't care, even a tiny bit, because it has no effect on my life.

Which is fine, no need to get too “complex” when doing this stuff, which is why I have tried to keep a lot of vectors and phaser math out of this thread despite my training-per Ben’s request.

Just realize that for some of us, we cannot “imagine” a world without:

 

[Besoeker]

Wired haired fox terrier, my avatar is him, jumper was his name.

Well, I suppose that could still be construed as vaguely on topic.
Mine is Max as of Max and Min voltages.

 

[LarryFine]

A Jumper wire.

 

[Besoeker]

A Jumper wire.

:thumbsup: