How does current flow in a circuit?

[chris kennedy]

You engineers can not even answer a simple question.

How does current flow in a circuit?

Completely

Finally! After a half dozen threads, a few years and thousands of post we have the answer to phasors, vectors and PF. Thanks Bob.

One more question, is there life after death?:roll:

 

[LarryFine]

I'll take 1 cup, two cream & two sugars . . .

Wassa matter? You don't like the taste of coffee?







J/K ~ That's my response to criticism about my ketchup use. "Wassa matter, you don't like the taste of (whatever)?" I ask how they like their coffee, then ask them that.

 

[LarryFine]

I have demonstrated HOW "a single phase, 20 amp load connected line-neutral with (Has) no neutral current".

Actually, you demonstrated how three of them have no neutral current.

 

[mivey]

Yes it all relates back to KCL....

But...

-Ia-Ib-Ic=In.

... is just an algebraic variation in the writing of the equation: Ia + Ib + Ic + In = 0.

In = Ia<A + Ib<B +Ic<C

... is not.

Sure, play favorites.

In=Ia+Ib+Ic= 0

 

[mivey]

Wassa matter? You don't like the taste of coffee?
J/K ~ That's my response to criticism about my ketchup use. "Wassa matter, you don't like the taste of (whatever)?" I ask how they like their coffee, then ask them that.

I prefer a milkshake. I bleed ketchup.

Actually, you demonstrated how three of them have no neutral current.

I can see your true wisdom revealed in the words you type.

 

[neutral]

I have worked with a lot of Electrical Engineers and some couldn?t tie their shoes or walk and chew gum at the same time, or able to use basic hand tools, but they knew a lot of electrical theory and how current flows in a circuit. If you can get an electrical engineering degree now without knowing basic Electrical theory, then is it any wonder why we are losing jobs to other countries?

 

[Mayimbe]

Actually, you demonstrated how three of them have no neutral current.

And one too... Select one phase and tell me if it has neutral current? The other two phases are in an black box that you cant open.

I have worked with a lot of Electrical Engineers and some couldn?t tie their shoes or walk and chew gum at the same time, or able to use basic hand tools, but they knew a lot of electrical theory and how current flows in a circuit. If you can get an electrical engineering degree now without knowing basic Electrical theory, then is it any wonder why we are losing jobs to other countries?

Thats a very good question...

Forget the demo and bring donuts!

joke foot? Never heard that expression. Local phrase?

Is kind of local, I change a couple of things... Translated... Erase a couple of things... and then I posted it. I guess it did the work...

On my way to work somebody push me on the subway, and I dropped the donuts. It wasnt my fault... And the coffee felt down on the pen drive where I had the calcs using the symmetrical components to help the OP... So you have to excuse me...

Yes it all relates back to KCL....

But...

... is just an algebraic variation in the writing of the equation: Ia + Ib + Ic + In = 0.

Yes it is. But for me its wrong because the current doesnt flow from the load to the source, in a physical view of it. If somebody said thats OK, then you can say that the power comes from the load to the source as well... That said, I will stay with the Ia+Ib+Ic=In convention.

You engineers can not even answer a simple question.

[/I]

It depends on how you define a "simple question".

 

[Smart $]

...

Yes it all relates back to KCL....

But...

... is just an algebraic variation in the writing of the equation: Ia + Ib + Ic + In = 0.

Yes it is. But for me its wrong because the current doesnt flow from the load to the source, in a physical view of it. If somebody said thats OK, then you can say that the power comes from the load to the source as well... That said, I will stay with the Ia+Ib+Ic=In convention.

...

Current does flow from the load to the source... and vice-versa. Apparently you need to expand on your viewpoint. It does not matter which side of the load or source we are on. The currents are the same at the load end of the circuit as they are at the source end. Consider the equation at X0 of the wye transformer (as if this 4-wire circuit were the only one conducting) and tell me if it is any different?

To write your form of the equation, you have to adopt the convention that all currents flowing into a node are positive and all current flowing out of the node are negative. I refuse to adopt any convention that is totally unnecessary. Therefore, and quite simply, the sum of branch currents at a node equals zero.

 

[LarryFine]

And one too... Select one phase and tell me if it has neutral current? The other two phases are in an black box that you cant open.

Yes, but they must be connected to that black box. Your statement depends on their presence to be true.

I'm just sayin' . . .

 

[cschmid]

Now i have my coffee and donuts will be here in morning..they drank the coffee and ate the donuts at UPS when I went to send them..so please some one feed these guys a bone. I enjoy the read after they get started...:grin:

 

[Smart $]

Yes, but they must be connected to that black box. Your statement depends on their presence to be true.

I'm just sayin' . . .

Actually, using the "black box" method of analysis, neutral current cannot be examined if the connection to neutral (i.e. node) is within the box... meaning there is no neutral conductor, only a two-terminal source functioning within stated parameters.

 

[Smart $]

Sure, play favorites.

Busted

 

[cschmid]

I believe with the type of load mentioned we can not have a perfectly balanced load. due to the nature of the load and many other loads on our systems the nature of a balance load might not exist. Non-sinusoidal and nonlinear loads are produced by ordinary household and office equipement. :grin:

 

[Mayimbe]

Current does flow from the load to the source... and vice-versa.

Please, I need an example to visualize that.

Apparently you need to expand on your viewpoint. It does not matter which side of the load or source we are on. The currents are the same at the load end of the circuit as they are at the source end.

Say you have a bus bar connected to a 1 kVA generator (1 Vac) on one side, in the other side you have 4 branch connected each one to a load. This loads consume 250 VA continuisly. They dont need to have a neutral since is an ideal scenario. Balanced system.

In this scenario, it does matter which side we are on. And the currents are not "the same at the load end of the circuit as they are at the source end" as you say.

Consider the equation at X0 of the wye transformer (as if this 4-wire circuit were the only one conducting) and tell me if it is any different?

X0?? Is that where the neutral is connected??. What transformer?? Im lost here...

To write your form of the equation, you have to adopt the convention that all currents flowing into a node are positive and all current flowing out of the node are negative. I refuse to adopt any convention that is totally unnecessary. Therefore, and quite simply, the sum of branch currents at a node equals zero.

I can adopt the convention I want, and you too. The things is that is better to adopt the convention that represent in a good way whats happening in the reality. Otherwise, you will confuse yourself and the other persons that are interested in what you are doing.

"the sum of branch currents at a node equals zero." Gustav Robert Kirchhoff (12 March 1824 ? 17 October 1887).

I believe with the type of load mentioned we can not have a perfectly balanced load. due to the nature of the load and many other loads on our systems the nature of a balance load might not exist. Non-sinusoidal and nonlinear loads are produced by ordinary household and office equipement. :grin:

Yes, but you can always simulated this unbalanced system with a group of balanced system independent of each other. So its good to have things clear in how a balanced system behaves. and how to analyze it.

 

[Mayimbe]

Current does flow from the load to the source... and vice-versa.

Please dont tell me that in an A. C. circuit in the negative semicycle the current does flows from the load to the source. :roll:

 

[LarryFine]

Actually, using the "black box" method of analysis, neutral current cannot be examined if the connection to neutral (i.e. node) is within the box... meaning there is no neutral conductor, only a two-terminal source functioning within stated parameters.

Well, if the portion of the circuit feeding the individual load under question is 2-wire, the portion of the grounded conductor between the black box and the load would still carry the phase's full current.

If the entire individual load's grounded conductor is within the black box, then the load itself must be at least partially within the box, too. In that case, there is no grounded conductor for that load.

 

[mivey]

"the sum of branch currents at a node equals zero." Gustav Robert Kirchhoff (12 March 1824 ? 17 October 1887).

You conveniently left off the direction, which is a matter of preference. I think what he said was more like the sum of all currents into a node is zero.

 

[mivey]

Please dont tell me that in an A. C. circuit in the negative semicycle the current does flows from the load to the source. :roll:

??? What are you getting at? Please tell me what "AC" stands for.

 

[Smart $]

Current does flow from the load to the source... and vice-versa.

Please, I need an example to visualize that.

Please dont tell me that in an A. C. circuit in the negative semicycle the current does flows from the load to the source. :roll:

OK, I won't.

In the positive semi-cycle, current flows from the load to the source ...then there's what you said, too

Say you have a bus bar connected to a 1 kVA generator (1 Vac) on one side, in the other side you have 4 [perhaps you meant 3?] branch connected each one to a load. This loads consume 250 VA continuisly. They dont need to have a neutral since is an ideal scenario. Balanced system.

In this scenario, it does matter which side we are on. And the currents are not "the same at the load end of the circuit as they are at the source end" as you say.



X0?? Is that where the neutral is connected??. What transformer?? Im lost here...

Refer to following diagram. Node1 is X0.

I can adopt the convention I want, and you too. The things is that is better to adopt the convention that represent in a good way whats happening in the reality. Otherwise, you will confuse yourself and the other persons that are interested in what you are doing.

"the sum of branch currents at a node equals zero." Gustav Robert Kirchhoff (12 March 1824 ? 17 October 1887).

The point here is there is no need to state whether the current is entering or leaving the node. In [static-] phasor/vector analysis, the phase angle takes care of that (while all magnitudes are positive).

Yes, but you can always simulated this unbalanced system with a group of balanced system independent of each other. So its good to have things clear in how a balanced system behaves. and how to analyze it.

You can if you want, but symmetrical components analysis is not required.

 

[Smart $]

You conveniently left off the direction, which is a matter of preference. I think what he said was more like the sum of all currents into a node is zero.

He was just quoting what I wrote.

You can't say "into" a node because that implies only currents entering and not any that are leaving. Conversely, you can't say "from" a node, because that implies only those currents leaving. This is why I opted for the word "at".