Why is residential wiring known as single phase?

[jim dungar]

Two hots. One neutral.

Yep, Van and Vnb. Just like they are wired, so why is this way not acceptable?

 

[Besoeker]

Yep, Van and Vnb. Just like they are wired,

Two hots, two neutrals?
Not what I would do but I'll take your word for it.

 

[pfalcon]

If they are going it opposite directions at every point in time, how can you reasonably construe that as being in phase?

Because the definition of "In Phase" says the cross "Zero" at the same time and reach "Peak" at the same time. Polarity and magnitude are not a part of the definition for being "In Phase".

 

[kwired]

about 1/3 the way to 600 posts.

 

[pfalcon]

There is a small similarity between single-phase residential and three-phase.

I've had people complain that a machine wired "ABC" was "out of phase" with a machine wired "BAC". Um, no. AB is still AB. BC is still BC. CA is still CA.

Single-phase residential is "Single-Phase" because:

1) Both legs cross ZERO at the same time and PEAK at the same time and therefore are in-phase.
2) The polarity of BN is physically in the same direction as NA. Therefore they are additive.
* either B < N < A or B > N > A
3) The potential difference between any two points (between A & B) is directly proportional to the total distance, direction, and voltage of AB.

Therefore AB is a single-phase. N is used as a voltage divider and is only centered for convenience. Legitimately if we have need we can place N to create -40, +200 for legs without harming the circuit. We don't alter or change any phases simply by selecting the neutral point. We only proportion the voltage magnitudes.

That said, there is no good (that is, common) terminology to describe the different legs of a voltage divider. The English language in particular hates a vacuum. Therefore in layman terms, the word PHASE is now often used to describe the legs as the "positive phase" and the "negative phase".

As Mivey said earlier: Only if there's a compelling NEED to be TECHNICALLY CORRECT is this an issue. Properly they are the "Negative portion of the phase with respect to the Neutral" and the "Positive portion of the phase with respect to the Neutral". But who wants to say all that if there's no compelling need?

If someone needs to call the hots "Plus" and "Minus" or "Phase A" and "Phase B" to keep them separate: Okay. Go for it. Have at. They are colloquially correct and technically incorrect.

 

[kwired]

Single phase residential is different from single phase non residential?

This may guarantee another 150 posts

 

[gar]

120103-1303 EST

From where do you get the definition of "in phase" that says coincident zero crossings define "in phase".

Certainly not from physics, optics, acoustics, and the following found thru dictionary.com .

Idioms & Phrases
in phase

Also, in sync . In a correlated or synchronized way; in accord, in harmony. For example, If everyone were in phase we could step up the schedule , or John and Pat often say the same thing at the same time; their minds are perfectly in sync . Both versions of this idiom refer to physical phenomena. The first, dating from the second half of the 1800s, alludes to being at the same stage in a series of movements. The second, a slangy abbreviation of synchronization dating from the mid-1900s, alludes to exact coincidence in the time or rate of movement. Also see in step; phase in; for the antonym, see out of phase.


The American Heritage? Dictionary of Idioms by Christine Ammer.
Copyright ? 1997. Published by Houghton Mifflin.
Cite This Source

For example to phase speakers correctly you need to consider polarity. To create interference patterns as in a diffraction grating you need to consider polarity.

.

 

[Besoeker]

Because the definition of "In Phase" says the cross "Zero" at the same time and reach "Peak" at the same time.

Care to cite an official source for that definition?

 

[rbalex]

Care to cite an official source for that definition?

Cited much earlier (post 131) and routinely ignored, but this is a good as you will get from ANY mathematics text.

 

[ronaldrc]

My two cents again http://home.comcast.net/~ronaldrc/wsb/The_Edison_Neutral2.html

 

[david luchini]

Your reasoning went astray at the very beginning.See below

I'm afraid it is your reasoning that went astray from the building.

See 'N' is grounded and its voltage is 0V.

It doesn't matter if 'N' is grounded or not - its' voltage is 0V. So is L1's, so is L2's, etc. Voltage is the electric potential difference between TWO points. Saying N has 0V is meaningless because you are only referencing ONE point is the system.

So if the voltage vector from V1to N is 120V,the voltage vector from N to to V2 should be -120V,because the the voltage of N is taken as O V which is at higher voltage than -120V.The sum of two current vectors give the voltage at N.Their difference give the voltage at L1-L2.

You are still missing that fact that a vector has MAGNITUDE and DIRECTION. You are ignoring the DIRECTION component. The voltage vector from L1 to N has the same DIRECTION as the voltage vector from N to L2. So if the voltage vector from L1 to N is 120<0V, then the voltage vector from N to L2 is also 120<0. The sum (not the difference) of these two vectors gives the voltage from L1 to L2. Vl1-n + Vl2-2 = 120<0 + 120<0 = 240<0.

It should also be clear that if the voltage vector from L1 to N has a value of 120<0V, then the voltage vector from N to L1 would be the reverse of it. In other words Vn-l1=120<180V, which is the same as -120<0V.

 

[david luchini]

Don't you see a conflict in the words I have emphasized?

No, I do not see any conflict in the words you have emphasized. Would you prefer the wording of KCL that says "The algebraic sum of currents in a network of conductors meeting at a point is zero." It says the same thing with different verbiage and removes any "entering" and "leaving" confusion that you may have.

So explain why one node has current into and out of it, and the other one doesn't. Aren't these nodes A & B simply the opposite ends of the same piece of wire in a center-tapped transfromer?

Because that is how it works out with the directional reference I assigned to the load and source currents. I could have assigned different references., but the direction of the referenced currents doesn't matter as long as they are consistent throughout the calculations. Surely you know this.

Yes, the source currents are. My old circuits professor would have had a conniption if I said I had a node where "no current is flowing out" as that is not possible in the real world. He would have pointed out that somewhere I had assumed an incorrect current direction and made me redo the math.

So in other words, the results of my calculation are correct, but you still take issue with them. To what end? I'd say your old circuits professor would need to learn to be less rigid. In the real world the current flowing in a node is changes direction because it is alternating current. The current "reference" is unidirectional.

Remove the load #1 so now there is one load a-b. Would you still say that node b still has two currents entering and none leaving? If you do, then wouldn't you also need to say node n has two currents leaving but non entering?

Yes I would based on the way I referenced my currents. I don't see a problem with it. Lets say with your three load example you removed load #1 and load #2 so that only the load from B-N remained. Would you say that the load current "leaves" the source at N and "enters" the source at B. That sounds counter-intuitive to me for a B-N connected load...but it perfectly fine if that is the way you reference the currents.

 

[pfalcon]

120103-1303 EST
From where do you get the definition of "in phase" that says coincident zero crossings define "in phase".
Certainly not from physics, optics, acoustics, and the following found thru dictionary.com .

For example to phase speakers correctly you need to consider polarity. To create interference patterns as in a diffraction grating you need to consider polarity.

To "Phase Speakers" is technical jargon. Yes, matching phase (synchronizing) is crucial. Yes, polarity is crucial. No, they aren't the same thing. But what sound technician wants to load his mouth with "I have to match phase and polarity." when he can say "I need to match phase." and everyone who counts knows what he means? Do you ever "land a wire"? or are you retentive enough to say something like "I need to cut to length, strip the wire, land it, and tighten it down."

Care to cite an official source for that definition?

? in phase
: in a synchronized or correlated manner

Definition of SYNCHRONIZE
intransitive verb
: to happen at the same time
transitive verb
1: to represent or arrange (events) to indicate coincidence or coexistence

Synchronized and "In-phase" do not mean identical in shape which is where you appear to be trying to drive this. In fact, your very own oscilloscope demonstrates synchronization far beyond the definition. The waveforms are proportional in shape as well as being synchronized.

 

[pfalcon]

... See 'N' is grounded and its voltage is 0V.So if the voltage vector from V1to N is 120V,the voltage vector from N to to V2 should be -120V,because the the voltage of N is taken as O V which is at higher voltage than -120V.The sum of two current vectors give the voltage at N.Their difference give the voltage at L1-L2.

Emphasized is not correct: Value should be +120V; See below.
The sum of the vectors will give 240V; The difference will give 0V.

Using N as a reference to 0V and presuming V1>V2 then meter test points:
V1 = 120V
N = 0V
V2 = -120V

Vector drawings become:
V1-N = 120 @ 0
N-V2 = 120 @ 0
V1-V2 = 240 @ 0

V2-N = -120 @ 0
N-V1 = -120 @ 0
V2-V1 = -240 @ 0

 

[Besoeker]

Yes, polarity is crucial.

Got it in one.
Well done.

 

[Besoeker]

Emphasized is not correct: Value should be +120V; See below.
The sum of the vectors will give 240V; The difference will give 0V.

Using N as a reference to 0V and presuming V1>V2 then meter test points:
V1 = 120V
N = 0V
V2 = -120V

Will your meter show it as -120V?

 

[pfalcon]

Will your meter show it as -120V?

No.
To get the actual values you have to start at one end or the other and do the math.
V2/0, N/120, V1/240 then since the poster wishes to define N=0V perform the subtraction.

 

[gar]

120203-1549 EST

Using the search string

mathematical definition of in phase


A result is:

From answers.com and Britannica Concise Encyclopedia

In wave motion, the fraction of the time required to complete a full cycle that a point completes after last passing through the reference position. Two periodic motions are said to be in phase when corresponding points of each reach maximum or minimum displacements at the same time. If the crests of two waves pass the same point at the same time, they are in phase for that position. If the crest of one and the trough of the other pass the same point at the same time, the phase angles differ by 180? and the waves are said to be of opposite phase. Phase differences are important in alternating electric current technology (see alternating current).

Read more: http://www.answers.com/topic/phase-physics-in-encyclopedia-1#ixzz1lM0CrLJz

That clearly states that to be in phase a peak has to correspond with a peak and a trough with a trough. Note: crest is the positive peak, and trough is the negative peak.

Home > Library > Science > Sci-Tech Encyclopedia
The fractional part of a period through which the time variable of a periodic quantity (alternating electric current, vibration) has moved, as measured at any point in time from an arbitrary time origin. In the case of a sinusoidally varying quantity, the time origin is usually assumed to be the last point at which the quantity passed through a zero position from a negative to a positive direction.

In comparing the phase relationships at a given instant between two time-varying quantities, the phase of one is usually assumed to be zero, and the phase of the other is described, with respect to the first, as the fractional part of a period through which the second quantity must vary to achieve a zero of its own (see illustration). In this case, the fractional part of the period is usually expressed in terms of angular measure, with one period being equal to 360? or 2π radians. See also Phase-angle measurement; Sine wave.

amplitude and T is the period.">
An illustration of the meaning of phase for a sinusoidal wave. The difference in phase between waves 1 and 2 is φ and is called the phase angle. For each wave, A is the amplitude and T is the period.

Note: the use of positive zero crossing as a usual time reference for one wave.

.

 

[Besoeker]

No.
To get the actual values you have to start at one end or the other and do the math.
V2/0, N/120, V1/240 then since the poster wishes to define N=0V perform the subtraction.

Profound stuff.

 

[jim dungar]

In the real world the current flowing in a node is changes direction because it is alternating current.

What an absolutely specious statement.

Based on this we would never be able to apply KCL as alternating current has no known direction, it is always changing.