Why is residential wiring known as single phase?

[rbalex]

...Welcome fellow defector. I left when Mivey insisted power flowed outside the copper while current flowed inside the copper.

I always started from the real world; I was only in the Jungle as a missionary.

 

[gar]

120227-1430 EST

rbalex:

If the voltage periods start and end at the same time (which they damn well better for a single-phase transformer) then they must have the same fraction (t/P) at any time t in the period P; therefore, they have the same phase.

As a convenient point of reference choose the positive zero crossing of a sine wave as the starting point of a period. You can not use both the positive and negative slopes as the same starting point, because then you would be using a 1/2 cycle as the period rather than the full cycle.

Then V_AN does not start at the same time as V_BN. One or the other starts 180 degrees later or earlier than the other. Thus, they are not in-phase or of the same-phase.

It is true that V_NB is in-phase with V_AN.

.

 

[rattus]

As a courtesy to you: because your diagram isn't relevant to phase.

I will repeat for the last time: direction, polarity or whatever manner or order you decide to apply probes isn’t relevant to what phase is; nor is magnitude. By the definition you originally offered, the only relevant elements in the definition with respect to the OP are the period (P) of the voltage functions and the factional part of the period (t/P) as they advance through time. If the voltage periods start and end at the same time (which they damn well better for a single-phase transformer) then they must have the same fraction (t/P) at any time t in the period P; therefore, they have the same phase.

Note the definition of phase says nothing of magnitude (amplitude) or sign (polarity).

READ THIS FOR COMPREHENSION. Don't be caught by the Grand Teton's seductive illusion.

Any response not relevant to the definition you provided as it applies to the OP will be ignored. That is, you don't get to replace the definition, from behind the curtains.

So phasor diagrams are not relative to phase? The very name says they are. Phasors are written in terms of magnitude and phase! It is nonsense to claim otherwise.

Now for definitions:

At t=0, sin(wt) has advanced 0 degrees, but sin(wt + 180) has advanced 180 degrees. The difference in phase is always 180 degrees. Can you explain that?

 

[rbalex]

120227-1430 EST

rbalex:



As a convenient point of reference choose the positive zero crossing of a sine wave as the starting point of a period. You can not use both the positive and negative slopes as the same starting point, because then you would be using a 1/2 cycle as the period rather than the full cycle.

Then V_AN does not start at the same time as V_BN. One or the other starts 180 degrees later or earlier than the other. Thus, they are not in-phase or of the same-phase.

It is true that V_NB is in-phase with V_AN.

.

Convenience is not an element of the definition, nor is a common origin. Read the definition carefully; they must only each start and end at the same time from their own respective arbitrary origins. As you noted in 1471 “... From an analysis perspective they are all the same.” Thanks again

 

[gar]

120227-1534 ESR

rbalex:

Convenience is only because I could choose any point, but I need to choose some point.

If I am going to compare two time varying sine waves with one another of precisely the same frequency for the phase difference between them, if any, then I can do this with a snapshot in time and compare their displacement relative to each other. Or in time I can measure the travel time for one wave to reach a comparable point of the other waveform having stored the other waveforms position at the starting time of the measurement.

If our selected point is a positive zero crossing, then I do not have to discuss scaling. If some non-zero point is selected, then the two curves need to be normalized in amplitude.

V_AN and V_BN do not have positive zero crossings at the same time. Thus, zero crossings alone without slope information do not provide a unique time point within one cycle's period.

I did not understand your point of referencing my post 1471. I am not ignoring the comment but I do not understand it.

For those that want to introduce pulses or noise, don't. We are discussing sine waves so no harmonics or noise pulses.

.

 

[rbalex]

So phasor diagrams are not relative to phase? The very name says they are. Phasors are written in terms of magnitude and phase! It is nonsense to claim otherwise.

Now for definitions:

At t=0, sin(wt) has advanced 0 degrees, but sin(wt + 180) has advanced 180 degrees. The difference in phase is always 180 degrees. Can you explain that?

Since you haven?t tried to replace the definition, I?ll respond.

Phase and phasor are merely homophones, like affect and effect. They sound similar. Often they are confused; nevertheless, they have definite conceptual distinctions.

Phasors rotate and have magnitude and direction; phases oscillate and only period and origin are relevant. Used properly, phasors may be helpful to illustrate phases but they aren?t required to define them.

 

[rbalex]

120227-1534 ESR

rbalex:

Convenience is only because I could choose any point, but I need to choose some point.

If I am going to compare two time varying sine waves with one another of precisely the same frequency for the phase difference between them, if any, then I can do this with a snapshot in time and compare their displacement relative to each other. Or in time I can measure the travel time for one wave to reach a comparable point of the other waveform having stored the other waveforms position at the starting time of the measurement.

If our selected point is a positive zero crossing, then I do not have to discuss scaling. If some non-zero point is selected, then the two curves need to be normalized in amplitude.

V_AN and V_BN do not have positive zero crossings at the same time. Thus, zero crossings alone without slope information do not provide a unique time point within one cycle's period.

I did not understand your point of referencing my post 1471. I am not ignoring the comment but I do not understand it.

For those that want to introduce pulses or noise, don't. We are discussing sine waves so no harmonics or noise pulses.

.

While you must pick a common time to start and, where one of the functions crosses zero from negative to positive is fine, the definition does not impose a common origin for both functions; i.e., the period P and the fraction t/P over the period at any time t of a single-phase system will still be the same for either function.

I understood 1471 to mean you could not differentiate A sin ([ωt+φ]) from ?A sin ([ωt+φ]?180?) for determining period P and the fraction t/P over the period of a single-phase system. If I misapplied your intent, I apologize. (Remember I'm oscilloscope deprived.)

 

[Besoeker]

Are you asserting the driving voltage functions don't start at the same time?

They cross zero at the same time but going in opposite directions. That makes them NOT in phase.

 

[Besoeker]

No, because I know the difference between a physical inversion and a mathematical phase shift.

I know what happens in real life with such circuits.

 

[rbalex]

They cross zero at the same time but going in opposite directions. That makes them NOT in phase.

That means they're not synchronized.

 

[Besoeker]

Defending the Myth of the non-existent ?Second-Phase ?at all costs is a doctrine that verges on the cultic.

No cult. Just simple, plain common sense.
You have yet to explain how and why I_a and I_b are 180 degrees apart with a resistive load.
Yet they are.
The very simple explanation is that V_an and V_bn, the driving voltages, are 180 degrees apart.
How hard is that to understand?

 

[Besoeker]

That means they're not synchronized.

It means that they are not in phase.
Suppose you have a single phase circuit with a 0.8pf load.
Do you think that current and voltage are in phase?
And, if not, why not?

 

[rattus]

Phase Definition.

Phase Definition.

Here is the definition of phase and phase difference. I think anyone who reads it carefully will understand phase and phase angle and phase difference.

 

[rbalex]

It means that they are not in phase.
Suppose you have a single phase circuit with a 0.8pf load.
Do you think that current and voltage are in phase?
And, if not, why not?

Yes, they must have the same phase or Mr Ohm needs a phone call.

 

[Besoeker]

Yes, they must have the same phase or Mr Ohm needs a phone call.

The diagrams in post #1004 show currents in a resistive load.
Simple Ohm's law, of course.
The currents clearly do not occur at the same time.
Clearly, they are not in phase.
So the driving voltages cannot be in phase.
Which part of that don't you understand?

 

[Besoeker]

Yes, they must have the same phase or Mr Ohm needs a phone call.

With a 0.8pf load?
Surely you don't believe that?

 

[rbalex]

With a 0.8pf load?
Surely you don't believe that?

Of course I do, and so do you if you believe they have the same period P and t/P is the same for every value of t over the period. Remember they can each have a different origin; only t=0 must be common to their respective functions.

 

[rbalex]

Here is the definition of phase and phase difference. I think anyone who reads it carefully will understand phase and phase angle and phase difference.

View attachment 6524

Thanks for confirming my understanding as it relates to the OP that "Phase is the fractional part of a period through which time or the associated time angle wt has advanced from an arbitrary reference."

 

[Besoeker]

Of course I do,

Let me just get this right.
Are saying that the current and voltage are in phase with a 0.8pf load?

 

[rattus]

Bob is saying that V1 is in phase with itself (I believe that) and that V1 is in phase with its inverse. How can that be?