How does a typical residential utility transformer work?

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rattus

Senior Member
ronaldrc said:
Rattus me you Don and most on hear are on the same page.

Like I said most just confused phase and polarity, so please
don't start giving me a hard time.

You could reverse one of my scopes polarity and get your result
but it would not be correct.

Dag gon it and you know it.

And no Eric it would not blow anything. Not even leads or eyelets
or whatever.

I am with Eric. You would be connecting 120V to the EGC unless the EGC prong has been snipped off then you would apply 120V to the scope chassis.

Don't do it!
 

ronaldrc

Senior Member
Location
Tennessee
Hum

Iric I am old and even my Fleming Valve oscilliscope had isolation between the chassic and the Common lead jack.

They had a transformer to boost the B+ ask Rattus he shound know.
This give it isolation unless you jumpered it.
 

eric stromberg

Senior Member
Location
Texas
ronaldrc said:
Hum

Iric I am old and even my Fleming Valve oscilliscope had isolation between the chassic and the Common lead jack.

They had a transformer to boost the B+ ask Rattus he shound know.
This give it isolation unless you jumpered it.

Hey, but wait just a minute. We're still riding horses in Texas. :grin:
 

coulter

Senior Member
rattus said:
..."Vector" is an obsolete term in AC analysis although many still use it....
You got to stop shooting from the hip and speak with non-colloquial tongue. You were almost right. The term "vector power" was replaced with "phasor power" (happened way before my time). But this is part of the symmetrical components model and has to do with that dreaded word, "rotation'. Ohhh just hearing it makes me shiver - kind of like "Moustafa" (Sorry , got carried away a little.)


Anyway, from IEEE 100 (edited and paraphrased to keep it from being too complex - per your directive):

The phasor power can also be stated in terms of the symmetrical components of the voltages and currents as
S = m Summation (E I *)
where Ekr is the phasor representing the symmetrical component of kth sequence of the rth harmonic of the line-to neutral set of polyphase voltages at the terminals of entry. Ikr*is the conjugate of the phasor representing the symmetrical component of the kth sequence of the rth harmonic of the polyphase set of currents through the terminals of entry

Note: This term was once defined as ?vector power.? With the introduction of the term ?phasor quantity,? the name of this term has been altered to correspond. The definition has also been altered to agree with the change in the sign of reactive power.

rattus said:
A phasor does not necessarily rotate?. You use fixed phasors for example in describing the magnitude and phase angle of 3-ph voltages?..
Again you are almost right. Yes to the first part if you are using the term ?phasor? to describe an impedance. This is right from the IEEE 100:

By extension, the term ?phasor? can also be applied to impedance and related complex quantities that are not time-dependent.

But you are not correct for the second. Again from IEEE 100 (definition of phasor):

A complex number expressing the magnitude and phase of a time-varying quantity. Unless otherwise specified, it is used only within the context of steady-state alternating linear systems

The phrase, ?phase of a time-varying quantity?, is generally translated as (oh-oh, I?m doing it again) as, ?rotation?.

It would really help if you would use terms as they are defined in IEEE100. This colloquial use makes it hard to follow your reasoning.

carl
 

rattus

Senior Member
Carl,

You are misinterpreting the definition of "phasor". Just plain "phasor" does not vary with time.

"A complex number expressing the magnitude and phase of a time-varying quantity. Unless otherwise specified, it is used only within the context of steady-state alternating linear systems"

Yes! This is a fixed phasor. The function is indeed time varying, but the phasor provides only magnitude and phase. If we extend the term to impedances, we know they cannot possibly rotate.

These are fixed (static) phasors which are commonly used in steady state AC analysis:

Va = 120V @ 0
Vb = 120V @ -120
Vc = 120V @ -240
Z = 100 Ohms @ -30

Rotating phasors are functions of time which the above expressions are not!

I use the adjectives "fixed" and "rotating" to distinguish between the two.
 
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LawnGuyLandSparky

Senior Member
closed-thread-prohibition.jpg
 

coulter

Senior Member
rattus said:
...Just plain "phasor" does not vary with time. ... This is a fixed phasor. ...

"Just plain phasor" is not defined in in ieee 100.
"fixed phasor" is not defined in in ieee 100.

rattus said:
... If we extend the term to impedances, we know they cannot possibly rotate. ...
Is there an echo in here. I think I just said that.

I usually try to not say things more than once. My theory is if you didn't get it the first time, saying it louder and more often does not add additional information - nor make what I am saying any more true.

rattus said:
...I use the adjectives "fixed" and "rotating" to distinguish between the two.
Yes, I honestly did read your posts - all of each one. I made an honest attempt to understand your reasoning. I even gave you the courtesy of assuming you had a valid point to make.

So, I think I got that - probably the first time you used the terms - at least by the end of the first post where you used them.

Imprecise, colloquial, describing concepts already defined by ieee 100 they are - but your's to use none the less.

Off to more important things. First snow today. Got to go play with my kid. Maybe take my dad a cup of coffee.

later

carl
 

rattus

Senior Member
Stonewall?

Stonewall?

Carl,

You are stonewalling me. Many terms not defined in IEEE 100 are in common usage. Various authors over the years have used various terms to describe the same thing. For example, the term "unit rotating phasor" is used in,

[van Valkenburg, "Network Analysis", Prentice-Hall, 1955]

Furthermore, I doubt that many of our members have a copy of IEEE 100.

But back to IEEE 100. From your own quote, a phasor is defined as,

"A complex number expressing the magnitude and phase of a time-varying quantity. Unless otherwise specified, it is used only within the context of steady-state alternating linear systems".

There is no rotation implied in this definition. It is what some authors call a "fixed phasor".

You are sidestepping the issue by hiding behind the IEEE standard. So cut out the pedantics and rebut my criticism.
 

coulter

Senior Member
Done playing in the snow. Had coffee with my dad. Back from the piano lesson.

And - tried to post. Spent 1/2 hour composing it. Fat fingered it and wiped it out - gone. I'm guessing a higher power is sending me a message. Which is likely okay - I did not have any new information or ideas.

So I guess this one is signed:

The Pedantic Stonewaller
(Brother to the Lone Haranguer)

I'm a single mom this week. Young son and I are off to bake banana bread.

later
 

coulter

Senior Member
rattus said:
...You are sidestepping the issue by hiding behind the IEEE standard. ...
Well, that would fit my signature wouldn't it?:D

rattus said:
...I doubt that many of our members have a copy of IEEE 100. ...
Can't help with this one. I would consider the ieee the governing authority for these concepts. They are the ones with the peer reviewed standards, practices, papers. You certainly have the choice to not use their definitions.

rattus said:
... For example, the term "unit rotating phasor" is used in,

[van Valkenburg, "Network Analysis", Prentice-Hall, 1955]. ...
Haven't read his book. But I'll bet he defined the term - and his definition did not conflict.

rattus said:
...From your own quote, a phasor is defined as,

"A complex number expressing the magnitude and phase of a time-varying quantity. Unless otherwise specified, it is used only within the context of steady-state alternating linear systems".

There is no rotation implied in this definition. It is what some authors call a "fixed phasor". ...
You must have missed my answer on this. It was in post 65. I've already discussed my attitude on repeating.

rattus said:
...You are stonewalling me. ...
Oh yeah - big time. Glad you picked up on that. I realized I was done when you said I was making this "too complicated". My translation was this discussion did not make a logical extension to mathamatical models, symetrical components, rotating equipment.

rattus said:
... So cut out the pedantics and rebut my criticism.
I didn't even know what "pedantics" is (are?). But it sounded like a putdown, so I looked it up in my Funk and Wagnalls. (See there I can use sometning besides ieee 100). I'm going to pick 2c, "A formalist or precisionist in teaching."

Okay, I'll except that. The concepts for symmetrical components, rotating equipment, power systems analysis, are pretty well defined. My inclination is to stick with the governing authority definitions. (But it still sounds like a mean putdown)

Regardless, I can't rebut your critism. As I understand, you choose to land the low side of a two channel scope on a single phase neutral, the high side probes on L1, L2. When you see the resulting signals show as 180 out, you then choose to represent this as two "fixed, non-rotating, phasors connected tail to tail" (Ouch that hurt to type).

Okay, I certainly can't refute your choice to do that. It isn't IDHL or illegal. It's okay with me.

signed

The SSPSH
(single subject pedantic stonewalling haranguer)
 

rattus

Senior Member
Carl,

I will respond to your last comment,

"Regardless, I can't rebut your critism. As I understand, you choose to land the low side of a two channel scope on a single phase neutral, the high side probes on L1, L2. When you see the resulting signals show as 180 out, you then choose to represent this as two "fixed, non-rotating, phasors connected tail to tail" (Ouch that hurt to type)."

No problem with the tail to tail connection. You would end up subtracting one voltage from the other, that is,

V12 = V1n - V2n

I have tried to make the point that the tails of the phasors in a 3-ph wye are all tied together as well. We obtain the line-line voltages in the same way--just use phasor math.

Of course it is second nature to merely add the magnitudes of V1 and V2, but it is also correct to consider V1n and V2n to be 180 degrees out from each other.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
rattus said:
Jim and Eric have grudgingly admitted as much...

I am not sure what you think I am grudgingly agreeing with.

I do not advocate the use of the term 180? when describing single phase systems. While it does exist when using the neutral as the reference point not all systems have a neutral. I do not believe that one set of terminology (i.e. the definition of phase voltage) should be used with 120/240V 1PH 3-wire systems, a different set with 240/120 3PH 4-wire, and still a different one with a 240Y/136V 3PH 3-wire.
 
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