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

[__dan]

Dan, wouldn't the other two primaries now be connected in series across the two still-hot primary phases, i.e., in parallel with the still-fully-energized primary? Wouldn't they now each see half of their original line-to-line voltage, and create two 60-volt sources? Of course, there would no longer be a phase difference, but wouldn't there now be 120, 60, 60?

Yep, I was thinking the same thing after I posted. Drop one line side leg of the delta and you will have one winding at full voltage and the other two in series with the same voltage. By eye I had put in 0 for the dropped leg but it will not be 0. It will float in the middle with the secondary load, a voltage divider.

I am thinking possibly you could short one of the secondary windings and the 120 will appear on the other, but IDK. I was actually thinking, why don't I have one hooked up that I can single phase the primary and measure the secondary voltages. Then I would short the 60 volt secondary and see what happens.

Once I could observe the physical reality, backing the math out of it would be easier.

 

[Besoeker]

Phase is a mathematical expression used to define a relationship between two points.

Between two different wave forms.

The difference between two different points occurring at any instant in time tells you nothing about phase or frequency or even whether it is an alternating wave form. Could be DC even.

 

[jaggedben]

I mean what's electricity got to do with geometry? Nothing, other than the convention we have invented to tie them together.

It's a convention that was conceived because it has utility for certain engineering purposes, such as sizing conductors and constructing transformers and so on. That utility depends pretty much entirely on the assumption that voltage waveforms maintain constant ideal forms. For said engineering purposes that assumption is usually fine.

So then, the interesting part, to me at least, is showing the limits of that engineering utility when real world conditions aren't ideal. One 'debate' in this thread is about using inversion vs. 180deg shift. In the ideal situation, they produce the same mathematical result so it really doesn't matter. But I think that when it comes to assymtrical distortion of the voltage waveform, there's a right answer as to which maintains greater accuracy. There are other variations from ideal waveforms about which that would not necessarily be true. I find it interesting how many engineers on this thread seemingly don't want to go there.

 

[jumper]

Between two different wave forms.

The difference between two different points occurring at any instant in time tells you nothing about phase or frequency or even whether it is an alternating wave form. Could be DC even.

Fine, two points between two different waveforms.

 

[Besoeker]

Fine, two points between two different waveforms.

Of the same frequency. Of course they could be of quite different amplitudes so it still wouldn't define phase difference.

 

[jumper]

Of the same frequency. Of course they could be of quite different amplitudes so it still wouldn't define phase difference.

And Ben wonders why I did not not want to define “phase”.

One small misstep is deadly around here.....

 

[Besoeker]

And Ben wonders why I did not not want to define “phase”.

One small misstep is deadly around here.....

Been fun.

 

[jumper]

Been fun.

Yep!

 

[jumper]

It's a convention that was conceived because it has utility for certain engineering purposes, such as sizing conductors and constructing transformers and so on. That utility depends pretty much entirely on the assumption that voltage waveforms maintain constant ideal forms. For said engineering purposes that assumption is usually fine.

So then, the interesting part, to me at least, is showing the limits of that engineering utility when real world conditions aren't ideal. One 'debate' in this thread is about using inversion vs. 180deg shift. In the ideal situation, they produce the same mathematical result so it really doesn't matter. But I think that when it comes to assymtrical distortion of the voltage waveform, there's a right answer as to which maintains greater accuracy. There are other variations from ideal waveforms about which that would not necessarily be true. I find it interesting how many engineers on this thread seemingly don't want to go there.

Analogy: You are trying to get a flower to bloom in no mans land during the Battle of the Somme. I wish we could but opinions seem to be entrenched. Usual story.

 

[Carultch]

It's a convention that was conceived because it has utility for certain engineering purposes, such as sizing conductors and constructing transformers and so on. That utility depends pretty much entirely on the assumption that voltage waveforms maintain constant ideal forms. For said engineering purposes that assumption is usually fine.

So then, the interesting part, to me at least, is showing the limits of that engineering utility when real world conditions aren't ideal. One 'debate' in this thread is about using inversion vs. 180deg shift. In the ideal situation, they produce the same mathematical result so it really doesn't matter. But I think that when it comes to assymtrical distortion of the voltage waveform, there's a right answer as to which maintains greater accuracy. There are other variations from ideal waveforms about which that would not necessarily be true. I find it interesting how many engineers on this thread seemingly don't want to go there.

The utility in representing electrical waveforms with geometry has to do with the nature of capacitance and inductance, with voltage across the component depending on a calculus manipulation of the current, instead of just the current itself (as is the case for resistance). Capacitance makes voltage depend on integration of current as charges accumulate, and inductance makes voltage depend on the derivative of current or instantaneous rate of change.

Derivatives and integrals of a pure sine wave are shifts in amplitude ("size of the wave") and phase (where within the cycle the wave is, at time t=0, measured as an angle from a standard starting point). And as such, these concepts can be represented as scaling and rotation respectively on the polar coordinate complex number plane. The real axis represents what happens for current or voltage in "real time", and the angle around the complex number plane represents time-variable for the schedule for the future and the record of the past. Smart$'s avatar is a great visual aid. When combining currents or voltages that are out of phase, representing them with this geometry allows us to add them up as we do with the geometry concept of vectors. Place them head-to-tail, and draw from first head to final tail.

 

[K8MHZ]

The original 'split phase' was DC.

A split-phase or single-phase three-wire system is a type of single-phase electric power distribution. It is the AC equivalent of the original Edison three-wire direct-current system. Its primary advantage is that it saves conductor material over a single-ended single-phase system, while only requiring a single phase on the supply side of the distribution transformer.^[1]

https://en.wikipedia.org/wiki/Split-phase_electric_power

 

[jumper]

I truely do not like the term split phase.

How can one “split” a phase?

 

[ggunn]

I truely do not like the term split phase.

How can one “split” a phase?

Run it through a center tapped transformer, maybe? <ducks>

 

[ggunn]

Of the same frequency. Of course they could be of quite different amplitudes so it still wouldn't define phase difference.

And that amplitude can have a negative sign in front of it.

 

[jumper]

Run it through a center tapped transformer, maybe? <ducks>

Can’t. POCO does not provide one for a 120/240V Single Phase Service.

 

[SG-1]

It's a continuously time varying signal. On what basis would you pick a particular instant in time? The dots tell you all you need to know.

Here is an explanation from J. Lewis Blackburn & Applied Protective Relaying, 1982 edition. The arrows, +/- show up on the protective relay terminal diagrams as well as the instrument transformers that feed them.

 

[jumper]

Here is an explanation from J. Lewis Blackburn & Applied Protective Relaying, 1982 edition. The arrows, +/- show up on the protective relay terminal diagrams as well as the instrument transformers that feed them.

Crapola! I just got a PM 2 days ago on Blackburn and relays and you wanna bring them into the discussion....Not fair INO.

 

[Besoeker]

And that amplitude can have a negative sign in front of it.

It can. Whether it means anything is another matter.

 

[K8MHZ]

I truely do not like the term split phase.

How can one “split” a phase?

It's done all the time and leads to half phased discussions like this one.

 

[jumper]

It's done all the time and leads to half phased discussions like this one.

Ah, that explains it!