A little more fun:

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Agreed!

Agreed!

Rick Christopherson said:
The difference between the two drawings is that Smart$ used vector subtraction, and I used vector addition. It is simply personal preference. I prefer to always use vector addition. It doesn't matter when there are only two vectors, but when you get into a more complicated problem with multiple vectors, then addition is more straight forward.
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Agreed,

Whether you subtract a phasor or change its sign and add, it doesn?t matter because the processes are identical, and I see nothing in Kirchoff to favor one wording over the other.

There is no such thing as "negative magnitude" either.

Now, please explain your repeated references to my error since you agree that subtraction of phasors is OK. My results were correct as well.
 
rattus said:
Now, please explain your repeated references to my error since you agree that subtraction of phasors is OK. My results were correct as well.
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You have a very short memory. I never said you couldn't subtract vectors, and I even provided the reference that you kept asking for on the matter.

You drew your vector backwards. According to your "yuck" diagram the voltage from G to C is positive in magnitude. Your diagram wasn't solving an equation, it was defining a system.
rattus said:
There is no such thing as "negative magnitude" either.
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You keep saying this, but you are the only one that is forcing a magnitude to be negative with your diagram. No one has ever suggested that a magnitude should be negative, but yours is forced to be negative because of the way you drew it.

Because a phasor cannot have a negative magnitude, it always points toward increasing values. This means that point C is 120 volts greater than point G. Likewise, point A is 120 volts greater than G. This forces points A and B to be equal. I don't know how you wire your panels, but I usually try to have 240 volts between phases.
 
Huh?

Huh?

Rick Christopherson said:
You drew your vector backwards. According to your "yuck" diagram the voltage from G to C is positive in magnitude. Your diagram wasn't solving an equation, it was defining a system.You keep saying this, but you are the only one that is forcing a magnitude to be negative with your diagram. No one has ever suggested that a magnitude should be negative, but yours is forced to be negative because of the way you drew it.
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Not so. I can draw phasors in one of two directions as long as I get the phase angles correct. And, magnitudes are absolute values. Not even Superman could force a magnitude to be negative. You admit as much below.
Because a phasor cannot have a negative magnitude, it always points toward increasing values. This means that point C is 120 volts greater than point G. Likewise, point A is 120 volts greater than G. This forces points A and B to be equal. I don't know how you wire your panels, but I usually try to have 240 volts between phases.
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Not so either. That is what the 180 degree phase difference is all about. These voltages are not equal; they are inverses of each other, therefore their difference is 240Vrms. Plot it out on one of your CAD systems. There is a serious misunderstanding here!
 
rattus said:
Not so. I can draw phasors in one of two directions as long as I get the phase angles correct.
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What? The phase angle is what is dictating the direction. If you have a phase angle, that's it--there is no option to make it go in two directions. A phase angle of zero points to the right and a phase angle of 180 points to the left (for our common coordinate system).

Show me a reference to support your concept.
rattus said:
Rick Christopherson said:
This means that point C is 120 volts greater than point G. Likewise, point A is 120 volts greater than G. This forces points A and B to be equal.
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That is what the 180 degree phase difference is all about.
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Absolutely not!! The 180 degrees already dictates its direction, you are trying to use it twice to form a double-negative. Show me where in your diagram how you are indicating that point B is not higher than point G.
rattus said:
These voltages are not equal; they are inverses of each other, therefore their difference is 240Vrms.
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The voltages are not inversed, only your point of reference makes them appear inverse. Where in a phasor diagram does it permit for a point of reference. Your equations can have a point of reference, but a phasor diagram cannot. Furthermore, if you were somehow claiming G as your point of reference, then all of your phasors should have been referenced to this same point.

Show me a reference that supports this concept.
rattus said:
And, magnitudes are absolute values. Not even Superman could force a magnitude to be negative. You admit as much below.
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Actually, after giving this more thought, I was only repeating what you had previously stated--and for that, I was mistaken. There is nothing in vector analysis that states a magnitude cannot be negative. As a matter of fact, it is required for doing subtraction by adding the inverse (see my previous text book reference).

I have already shown you a text book reference that supports this, so you show me the text book reference that contradicts this.
rattus said:
There is a serious misunderstanding here!
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Yes, there certainly is, and it is your misunderstanding of vector analysis. If you go back to the thread that you started, "AC Circuits," you will see that I listed a full year of Vector Analysis. I also noticed that you didn't list any Vector Analysis in your own response. Was this just an oversight?
 
Rick Christopherson said:
You have a very short memory. I never said you couldn't subtract vectors, and I even provided the reference that you kept asking for on the matter.

You drew your vector backwards. According to your "yuck" diagram the voltage from G to C is positive in magnitude. Your diagram wasn't solving an equation, it was defining a system.You keep saying this, but you are the only one that is forcing a magnitude to be negative with your diagram. No one has ever suggested that a magnitude should be negative, but yours is forced to be negative because of the way you drew it.

Because a phasor cannot have a negative magnitude, it always points toward increasing values. This means that point C is 120 volts greater than point G. Likewise, point A is 120 volts greater than G. This forces points A and B to be equal. I don't know how you wire your panels, but I usually try to have 240 volts between phases.
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Yes additive voltages add up to 240 they are additive not subtractive to add to zero. The current is moving in the same direction on the SINGLE winding Therefore the voltage vectors MUST be in the same direction because the CURRENT vectors are in the same direction ad neauseum. As Rick says 240 volts is the norm around here not zero. HELLO!!
 
Rick Christopherson said:
Because a phasor cannot have a negative magnitude, it always points toward increasing values. This means that point C is 120 volts greater than point G. Likewise, point A is 120 volts greater than G. This forces points A and B to be equal. I don't know how you wire your panels, but I usually try to have 240 volts between phases.
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Regarding your statement that I underlined and highlighted...
No, it does not. At least not at the same point in time. If you were to time-shift one or the other by 180? degress, then they would be equal... but that is not the case.

As for negative magnitudes, you are confusing operands with magnitudes. If we consider a numerical value as a scalar magnitude, then the following are true:
1 + 1 + 1 = 3, we have all positive "magnitudes".
3 – 1 – 1 = 1, we have all positive "magnitudes"... the equation uses the minus operand.
1 + (-1) + (-1) = -1, we have one positive and three negative magnitudes.
1 – (-1) – (-1) = 3, we have two positive and two negative magnitudes and while the result is the same as the first equation above, it is not the same equation.​

FWIW, I did not participate in those other threads because I knew they would accomplish no more than wasting my precious "happy" time. I'll not waste any more time on this thread. The issue is moot. If it works for the purpose at hand, that's all that matters.
 
To subtract or not to subtract?

To subtract or not to subtract?

Rick,

A phasor is defined as a complex number which provides a magnitude and phase angle of a sinusoid. There is no requirement that it point in one direction or the other. In fact your very own example points toward a lower voltage--ground!

You should understand that in general Vxy = -Vyx. And in this case,

120V @ 180 = - 120V @ 0

No, the magnitude is not negative! The real and imaginary components are negated, that is they are flipped about their axes.

You must provide a reference to prove your argument that the direction of a phasor must point in a particular direction. If you can't or won't, I will just assume you made up that rule!

If there were such a rule, the delta voltage diagram could never be closed!


P.S. When you imply that 120 @ 0 = 120 @ 180, I know you misunderstand!
 
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Rick Christopherson said:
...You drew your vector backwards...Because a phasor cannot have a negative magnitude, it always points toward increasing values...
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A phasor can point any direction it wants to. A phasor of Vcg is just as valid as a phasor of Vgc.

Take the delta system. I can draw 1,000 phasors with that delta if I want. They do not have to be restricted to going from one specific terminal to another. I can pick a point 1/3 of the way down the coil of one transformer and draw a phasor to the midpoint of another coil, or vice versa.

Maybe that is where the confusion comes in. A phasor diagram is NOT a circuit diagram. If you show only certain phasors with certain directions, and use a closed phasor diagram, it can LOOK like the circuit diagram.

Rick Christopherson said:
What? The phase angle is what is dictating the direction. If you have a phase angle, that's it--there is no option to make it go in two directions. A phase angle of zero points to the right and a phase angle of 180 points to the left (for our common coordinate system)...Where in a phasor diagram does it permit for a point of reference. Your equations can have a point of reference, but a phasor diagram cannot. Furthermore, if you were somehow claiming G as your point of reference, then all of your phasors should have been referenced to this same point...
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Some of this is true, to a point. The problem is that the Vcg phasor and Vgc phasor point in opposite directions. I can pick any reference point I want for a phasor.

Rick Christopherson said:
Show me a reference to support your concept.
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There are many but How about Blackburn's "Protective Relaying - Principles and Applications" chapter 3?

[edit: while I can pick phasors any way I want, the circuit diagram will show the relationship between the phasors]
 
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Smart $ said:
Regarding your statement that I underlined and highlighted...
No, it does not. At least not at the same point in time. If you were to time-shift one or the other by 180? degress, then they would be equal... but that is not the case.


As for negative magnitudes, you are confusing operands with magnitudes. If we consider a numerical value as a scalar magnitude, then the following are true:
1 + 1 + 1 = 3, we have all positive "magnitudes".
3 ? 1 ? 1 = 1, we have all positive "magnitudes"... the equation uses the minus operand.
1 + (-1) + (-1) = -1, we have one positive and three negative magnitudes.
1 ? (-1) ? (-1) = 3, we have two positive and two negative magnitudes and while the result is the same as the first equation above, it is not the same equation.
​
FWIW, I did not participate in those other threads because I knew they would accomplish no more than wasting my precious "happy" time. I'll not waste any more time on this thread. The issue is moot. If it works for the purpose at hand, that's all that matters.
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Before you beat Smart$ up over what he said: The idea he was trying to point out is correct. Don't stress over him saying "negative magnitude". Use the idea that he is talking about a value that has a magnitude, but the overall value is negative because it is in the opposite direction. Call "positive magnitude" a value with a zero degree angle and "negative magnitude" a value with a 180 degree angle.
 
Smart $ said:
At least not at the same point in time. If you were to time-shift one or the other by 180? degress, then they would be equal... but that is not the case.
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Well that's exactly what he did--he shifted one by 180 degrees without negating the magnitude, and this results in points A and B being equal.
 
rattus said:
In fact your very own example points toward a lower voltage--ground!
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If it is your assertion that ground is at a lower voltage than B, then you are stating that points A and B must be equal.

rattus said:
You should understand that in general Vxy = -Vyx. And in this case,
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Where in your diagram is it identifying the vector between points B and G as being the voltage Vbg? You drew your vectors between labeled points--that's nodal analysis. If you wanted to assign Vbg to one of the vectors, then you cannot show the points B and G, and each vector is identified by its definition of Vag and Vbg.

rattus said:
120V @ 180 = - 120V @ 0
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Funny that you choose to negate the 120@0. What you have shown in your diagram is more applicable to -120@180 = 120@0. By your own admission here, if you are going to flip the vector by 180 degrees, you need to give it a minus sign to make is equal to where you started.

rattus said:
You must provide a reference to prove your argument that the direction of a phasor must point in a particular direction. If you can't or won't, I will just assume you made up that rule!
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Think about what you are saying. if a vector can have a random direction, then what good are they? You keep asking me to provide you with references, but you never provide any yourself. You already know that I am sitting here with a vector analysis text book in front of me, because you have already seen excerpts from it. Using your own words, if you can't or won't, I am assuming that you won't provide any references because you never took a course in vector analysis and don't have the text book to reference.
rattus said:
P.S. When you imply that 120 @ 0 = 120 @ 180, I know you misunderstand!
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I know full well these are not equal. It is your diagram that is trying make them equal!
 
Faulty premise:

Faulty premise:

Rick,

If you cannot support your premise, the conclusion is that your premise is faulty which means your entire argument is faulty. Then you are the one who is in error.

Case closed.
 
mivey said:
Well, you boys have fun. I'm going to join Smart$ in the other room.:)
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I was here first, before you two. And I have only looked in the window a couple of times.

carl
 
rattus said:
Rick,

If you cannot support your premise, the conclusion is that your premise is faulty which means your entire argument is faulty. Then you are the one who is in error.

Case closed.
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It is not me that is failing to support my premise. You are using your distraction technique again.

Address the issues in my previous posting that you conveniently ignored. I have provided you with several references to refute several things that you have stated over the course of this discussion, and to date, you have provided none. Find me the text book references that I have requested. Find me one text book example that shows the "yuck" diagram.
 
I’ll make this easy for you. You just need to find one reference.

Your phasor diagram requires subtraction to complete a KVL summation. Show me the reference that states you can intermix addition and subtraction for a KVL summation, and don’t say it is simply because the arrow is pointing the other way. It is directed summation, and you are already representing the direction with 180 degrees.

As I have already given you a reference, vector summation is commutative, and if you don’t understand what that word means, then you need to stop and look it up before you answer further.

Your diagram is not commutative because if you rearrange the vectors, you don’t get the same answer. This violates a basic principle of vector analysis. Your diagram is not a directed summation. It includes one step of directed subtraction, and that is why it doesn’t satisfy KVL, or vector commutation.

You can’t simply rewrite the laws of circuit analysis just to suit your diagram.

So explain how you can meet KVL and commutation with the diagram that you have drawn? Show me the reference that says you can intermix directed addition and directed subtraction in the same loop.

Edit: This is related, so I am going to add this here. If you are going to claim that "Summation" means both subtraction and addition, then provide the reference to support it.
 
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