phase rotation

[Hameedulla-Ekhlas]

Greeting all,
I am reading a topic regarding to phase displacement and it says


Phase rotation is always anti-clockwise. (international adopted convention)


Is the red line true?

 

[cadpoint]

I thought they called it the "right hand rule" as the power goes forward it curls like the fingers in your hand. Look Up "right hand rule"

 

[ohmhead]

Well read this i found it interesting it explains it .http://www.marcspages.co.uk/pq/3120.htm

 

[Jraef]

Greeting all,
I am reading a topic regarding to phase displacement and it says


Phase rotation is always anti-clockwise. (international adopted convention)


Is the red line true?

No. It is what it is. I live in Northern California where PG&E, the largest utility, is ACB rotation whereas most of the rest of the US is ABC rotation. Not that it matters though, unless someone has designed a Phase Reversal Relay that assumes the ABC convention (and I have run into them).

 

[Smart $]

Greeting all,
I am reading a topic regarding to phase displacement and it says


Phase rotation is always anti-clockwise. (international adopted convention)


Is the red line true?

Its true in the sense that is how it supposed to be, i.e. that's how it is supposed to be generated TTBOMK. But simply flopping any two lines will change rotation on any standard 3? system.

There are times when even under code the rotation is changed. For instance, when POCO furnishes a 4-wire delta supply (aka hi-leg service) they may place the hi-leg on line C because that is where it has be for their meter to work properly. However, the NEC requires premises wiring to put the hi-leg on line B... so POCO C is flopped to premises B, thus changing rotation to clockwise. Unless of course POCO takes this into consideration and pre-flops C so the premises flop puts rotation back to "counter-clockwise". In wiring services, the only way to know for sure is to check with a phase rotation indicator.

 

[cadpoint]

Talking out of context to the link:
I don't know, I didn't like the magnetic reference to north cause that's really the oppose pole (pointing), that's showing direction to north; nor the inference to a propellar Here because that an object set in motion to do work! The propellar like spinning tires is an eye illusion.

 

[Hameedulla-Ekhlas]

thanks all for useful information.

 

[SG-1]

Greeting all,
I am reading a topic regarding to phase displacement and it says


Phase rotation is always anti-clockwise. (international adopted convention)


Is the red line true?

I cannot see the red line, do you mean the phasor rotation diagram that is shown on single & three line diagrams ?

 

[shepelec]

The POCO in my area always sets a clock wise rotation. In turn I ways keep the same rotation through the whole install. I also mark it on the cover of the panels and disconnects. This in turn allows the same rotation to be passed on to any motors as well. It makes start up alot easier if you know what direction evrything is going to turn.

 

[rattus]

Perhaps:

Perhaps:

Greeting all,
I am reading a topic regarding to phase displacement and it says


Phase rotation is always anti-clockwise. (international adopted convention)


Is the red line true?

Perhaps they mean that the arrows representing rotating phasors rotate in a CCW direction. For example, for the phase sequence abc, we would let the instantaneous voltages be,

va = 339V*cos(wt)
vb = 339V*cos(wt -120)
vc = 339V*cos(wt -240)

Then for the phase sequence acb, we could write

va = 339V*cos(wt)
vc = 339V*cos(wt -120)
vb= 339V*cos(wt -240)

In either case the arrows rotate CCW.

 

[Hameedulla-Ekhlas]

Perhaps,

Is the abc not clockwise?

 

[Smart $]

Perhaps,

Is the abc not clockwise?

When the sequence is noted, it should always be counter-clockwise:

ABC is CCW
ACB is CCW​

If the two were intended to be say alternate systems (such as double-ended supply from two different POCO's), you would not match B's and C's. Rather you would pair A-A, B-C, and C-B respectively on the connection to the gear.

Now if you happen to be talking about phasors, they are static when drawn and yes, their angular position to one another is clockwise (they stay put, you or rather your perspective moves), but the direction which the phasors rotate is counter-clockwise (they move, you stay put)... btw, don't wait for it to happen on paper

 

[SG-1]

Greeting all,
I am reading a topic regarding to phase displacement and it says


Phase rotation is always anti-clockwise. (international adopted convention)


Is the red line true?

J. Lewis Blackburn says the red line is true.

 

[rattus]

Much ado about not much.

Much ado about not much.

The term, "phase rotation" is confusing. "Phase sequence" is much more meaningful, that is for the sequence abc, the peaks of va, vb, and vc occur in the sequence abc. For the sequence acb, the peaks occur in the order acb. No need to worry about the direction of rotation.

 

[SG-1]

The term, "phase rotation" is confusing. "Phase sequence" is much more meaningful, that is for the sequence abc, the peaks of va, vb, and vc occur in the sequence abc. For the sequence acb, the peaks occur in the order acb. No need to worry about the direction of rotation.

Blackburn also makes a very simular comment.

 

[Smart $]

The term, "phase rotation" is confusing. "Phase sequence" is much more meaningful, that is for the sequence abc, the peaks of va, vb, and vc occur in the sequence abc. For the sequence acb, the peaks occur in the order acb. No need to worry about the direction of rotation.

That's fine on paper, but in the installation world, ABC and ACB don't mean much when experience has proven that predicting which way a motor will rotate when energized is a crap shoot

 

[mivey]

J. Lewis Blackburn says the red line is true.

Actually, he probably said the phasor rotation is CCW. If he used the term "phase rotation" I'm sure he did so in the context of "sequence".

As rattus has stated, phase sequence is the proper term. The term "phase rotation" is used but it is not what we might call "proper english".

Rattus properly covered phasor rotation in his post #10

 

[mivey]

That's fine on paper, but in the installation world, ABC and ACB don't mean much when experience has proven that predicting which way a motor will rotate when energized is a crap shoot

True enough, and the first questions would be: which one is A, which one is B, and which one is C. You just got to have a rotation meter in the field.

 

[rattus]

That's what I said:

That's what I said:

"Counterclockwise rotation has been adopted internationally as the positive direction of rotation of revolving time phasors." This convention applies to single phase and polyphase systems.

["Alternating Current Circuits", Tang, 1960]

 

[rattus]

That's fine on paper, but in the installation world, ABC and ACB don't mean much when experience has proven that predicting which way a motor will rotate when energized is a crap shoot

Whatever terms you use, you have the same problem.