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

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SG-1 said:
The beauty of a real 2 phase system is that with an angular displacement of 180 degrees the math stays on the real number line, at least for resistive loads or adding the voltages between coils.
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precisely what happens on the neutral with split phase

another scenario: suppose l2 is disconnected. do i still have potential (and therefore current phasor) in l1-n? of course. what if i attempt to turn on a 240V appliance-is it surprising when the incandescent lights on l2-n turn on?? would they work as expected? by turning on the appliance, a series circuit was created and there is only 120V available to drive the appliance and the backfed light bulbs. so the answer is probably not.
 
SG-1 said:
A very esteemed member here taught me this years ago.
The general formula to determine the number of phases in any system is: 360 degrees divided by the angular displacement between the phases equals the number of phases in that system.

360/120=3phases
360/180=2phases
360/360=1phase
360/90=4phases, but since only half of the system was needed & used it became misnamed two phase. An is still causing much confusion to this date.

The beauty of a real 2 phase system is that with an angular displacement of 180 degrees the math stays on the real number line, at least for resistive loads or adding the voltages between coils.
Click to expand...

I have a terminology quibble with the above. Based on this discussion I absolutely agree that 180 degrees is a different phase angle than 0 degrees, and thus I agree than in a balanced '2 phase' system you will have _4_ distinct phase angles.

The terminology quibble is in how this is normally used. I will go back to the literature on 'high phase order' motors. In a conventional 3 phase motor you have at least _6_ phase bands in the stator; 3 for each of the supply phases and 3 for the inverses of these. The inverse phase bands are required because you have coils for each of the phase circuits, and thus half of the conductors travel down the stator slots in one direction, and half go the other way. But this is still called a _three_ phase motor. What the HPO people call a six phase motor generally has 12 phase bands, and can be understood as two three phase coil sets displaced by 30 degrees.

As I have seen the terminology used, terminals with phase displacements of 180 degrees are considered separate parts of the same 'phase' for purpose of counting system phases. Thus a phase displacement of 90 degrees (which I agree has 4 separate phase angles available) is _called_ '2 phase', and a phase displacement of 180 degrees is _called_ single phase. A phase displacement of 120 degrees is called 3 phase, but if you look at how 3 phase is used to run motors you will clearly see 6 separate phase angles in use.

An exception to this seems to be in transformers for rectifiers; 'hexaphase' transformers have 6 terminals with a phase angle of 60 degrees, and a transformer for a 12 pulse rectifier has phase angle differences of 30 degrees.

-Jon
 
drktmplr12 said:
current is not the work performed. cancelled current means the sine waves are added together on the neutral and the result is zero.



E*I = S. E*I*cos (pf) = P. the equation you provided does not prove current is work.



how is current the work being performed? work is power per unit time. current is most certainly proportional to work, if that's what you are meaning to say.



a series circuit isn't "created" by having balanced loads on l1-n and l2-n. there are two current phasors that meet at the neutral and add (KCL) on the path back to the center tap. when you add the current phasors and the loads are equal, they cancel because they are 180 degrees out of phase with one another and the same magnitude. the moment you have imbalanced load, the difference in magnitude will appear on the neutral.



magnetic fields are created due to movement of charge.

current is the movement of electrons in response to an electric field. work is power per unit time.



current is flowing because the electrons forming a continuous path were subjected to an electric field. the work done depends on the current and voltage together.

let me ask the forum a question.

what if i operate a low power factor load on one leg of a split phase transformer while keeping the other leg purely resistive? how does this impact the magnetic field within the first and second halves of the secondary winding, if at all? will there be an measurable response in the opposite winding?

the current on l1-n will experience a phase shift. the current on l2-n will not. two phasors.
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Nothing but drivel here :cool:

no canceled currents - even ray Charles can see the series circuit created when 1 lead each of two components are connected together and the opposite ends of those components connect across a power supply.:D

Well, if current is proportional to work, then obviously work is being performed ;)

Glad to see you admit that current is not a magnetic field

electricity 101 - if there is no potential difference there is no current flow
 
Winnie,

It is a terminology issue. Trying to apply a term across different apps is troublesome. That is why if there is ever to be an agreement on a specific conclusion, we must agree on definitions on the front end. There are too many definitions to be had. Too many standards as well: "the nice thing about standards is that there are so many to choose from".

I understand what you are saying about the motors but I also understand that it will not align with everything. There are varying perspectives and each has merit in its own right.

Fun to talk about all this but a lot of the chat is a difference of opinion on what definition to use. That is an opinion and will never reach a conclusion. Discussing a specific definition is the interesting part.
 
SG-1 said:
First, thanks for those links, Mivey. Great training material.

Second some things I have learned from being here all these years:

If GAR or Mivey are trying to tell you something it is best to listen, because they know.

A very esteemed member here taught me this years ago.
The general formula to determine the number of phases in any system is: 360 degrees divided by the angular displacement between the phases equals the number of phases in that system.

360/120=3phases
360/180=2phases
360/360=1phase
360/90=4phases, but since only half of the system was needed & used it became misnamed two phase. An is still causing much confusion to this date.

The beauty of a real 2 phase system is that with an angular displacement of 180 degrees the math stays on the real number line, at least for resistive loads or adding the voltages between coils.
Click to expand...
Thank you for the confidence. I have been at this for a long time and I have learned much over the years, much more than I ever learned in school.

I have also learned quite a bit on this forum. The discussions are very helpful at times. Sometimes you think you know a topic until you look closer and find out there was more to it than you thought.
 
mivey said:
Disagree if you like but that is how it is with utility distribution transformers.

Dual leads are brought out and the windings can be connected in series or parallel. So even if you wanted to make a weak case on tap terminology for a single lead, that is not what we have.

Some links that may help you understand:

https://www.electronics-tutorials.ws/transformer/multiple-winding-transformers.html

http://www.idc-online.com/technical...engineering/Multiple_Winding_Transformers.pdf
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Control transformers - multiwinding yes; I use them regularly
Power transformers - multiwinding no; I use them regularly. Its called center-tapped for a reason. Next pole mounted distribution xfmr you see look to see how many nodes protrude from the case for secondary power - you'll see (3). L1 - N - L2 how will they reconnect?
 
buffalonymann said:
Control transformers - multiwinding yes; I use them regularly
Power transformers - multiwinding no; I use them regularly. Its called center-tapped for a reason. Next pole mounted distribution xfmr you see look to see how many nodes protrude from the case for secondary power - you'll see (3). L1 - N - L2 how will they reconnect?
Click to expand...

Maybe you could look at the transformer connections on page 4 , http://www.cooperindustries.com/con...es/library/201_1phTransformers/TC202001EN.pdf, and it will help you understand better.
 
buffalonymann said:
Control transformers - multiwinding yes; I use them regularly
Power transformers - multiwinding no; I use them regularly. Its called center-tapped for a reason. Next pole mounted distribution xfmr you see look to see how many nodes protrude from the case for secondary power - you'll see (3). L1 - N - L2 how will they reconnect?
Click to expand...
I have opened countless over the years. Some have all 4 terminals on the tank exterior bushings, some only have 3. For the ones with 3, you access the terminals on a terminal board inside the tank and for parallel operation you only connect to 2 of the external bushings.
 
buffalonymann said:
Next pole mounted distribution xfmr you see look to see how many nodes protrude from the case for secondary power - you'll see (3). L1 - N - L2 how will they reconnect?
Click to expand...
They have two independent secondaries. When connected for 240v, say for 1ph, the secondaries are placed in series and used as (grounded) center-tapped, using all three bushings, or Delta 3ph (with the center of only one grounded for high-leg). When connected for 120v, say for 208Y/120 3ph, the secondaries are placed in parallel and use only the left and (grounded) center bushings are used.
 
Personally, I never worked with pole mount transformers, always been POCO’s job.

But I have installed plenty of standard dry type ones and these type of diagrams are on every one. I picked this one for emphasis on 120/240V.


A072496F-D14F-4FA4-A8FF-0314AE678881.jpg
 
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buffalonymann said:
Control transformers - multiwinding yes; I use them regularly
Power transformers - multiwinding no; I use them regularly. Its called center-tapped for a reason. Next pole mounted distribution xfmr you see look to see how many nodes protrude from the case for secondary power - you'll see (3). L1 - N - L2 how will they reconnect?
Click to expand...

I looked at a multiwinding today
2 mva
12470 prim
600 delta sec1
950 wye sec2

a pole mntd util 'can' is a multiwinding
 
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mivey said:
I have opened countless over the years. Some have all 4 terminals on the tank exterior bushings, some only have 3. For the ones with 3, you access the terminals on a terminal board inside the tank and for parallel operation you only connect to 2 of the external bushings.
Click to expand...

:happyyes:
 
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