How does current flow in a circuit?

[Mayimbe]

See post #10. What is so "unpractical" about that?

post # 10 Its based on an unbalance currents presented by Besoeker.

What you did, was, Toke those currents assumed, and found the current that will flow on the neutral. Which is absolutely fine.

What I was saying is that if you dont have Besoeker at hand, and you dont know the unbalance current that will flow on each?phases. Then aplying basic trigonometry knowledge to find those current will be a bit unpractical.

Another issue is that "basic trigonometry" could mean something to me, that it wont necessary mean the same to you.

 

[mivey]

What I was saying is that if you dont have Besoeker at hand, and you dont know the unbalance current that will flow on each?phases.

So what? Then we will have to call Besoeker to set up a different analysis (what are the call rate to the UK anyway?).

You have to have some data if you want to model a system. The available data will help you determine the method you use. I see no need to get into symmetrical components with the OP when he is already struggling to understand current flow on a neutral.

 

[Mayimbe]

So what? Then we will have to call Besoeker to set up a different analysis (what are the call rate to the UK anyway?).

You have to have some data if you want to model a system. The available data will help you determine the method you use. I see no need to get into symmetrical components with the OP when he is already struggling to understand current flow on a neutral.

Exactly. With the data that the OP gives, a possible method to find the currents on the phases, is symmtrical components. Or simulate it on Matlab, Etap, Excel... And then use the post # 10 to find the In current.

I didnt know that the OP was struggling to understand the current flow on a neutral. How did you know that? If its true, then you are absolutely right when you say theres no need of gettin into sym comp. And it would make me sad. And I wont post never again when you do.

But the OP has to said it first.

 

[Besoeker]

So what? Then we will have to call Besoeker to set up a different analysis (what are the call rate to the UK anyway?).

Substantially lower than my consultancy fees.

 

[winnie]

All this vector addition is cool, but I think that Larry answered the original question in post #3.

I don't think that the OP was asking about how current combines on the neutral, but instead how a 20A line-line single phase load differs from a 20A line-neutral single phase load.

-Jon

 

[mivey]

I didnt know that the OP was struggling to understand the current flow on a neutral. How did you know that?

The same way Chris did:

...If for example I had an appliance that had a full load current of 20A...If it was phase to neutral I know that theoretically it would be 20A on the phase conductor with no current on the neutral, but what about phase to phase?

If its true, then you are absolutely right when you say theres no need of gettin into sym comp. And it would make me sad. And I wont post never again when you do.

And what would be the fun in that? :grin:

Besides, I'm not saying to not teach the OP symmetrical components, just that it seemed a little too involved at that point. Larry gave the simplest answer for the line-line connection and phase currents.

Besoeker was just illustrating Steve's point concerning the neutral currents.

If you think it would help the OP, then I think you should proceed with your symmetrical components example, but the OP is going to need more than what you have posted so far.

All this vector addition is cool, but I think that Larry answered the original question in post #3.

Partially.

I don't think that the OP was asking about how current combines on the neutral, but instead how a 20A line-line single phase load differs from a 20A line-neutral single phase load.

But demonstrated a fundamental misunderstanding of circuits, which prompted more discussion. See above. Chris picked that up in post #4.

 

[Mayimbe]

The same way Chris did:

From the "no current on the neutral" part. I could easily inferred that he was talkin about a balance system. Not that he was struggling to understand...

If you think it would help the OP, then I think you should proceed with your symmetrical components example, but the OP is going to need more than what you have posted so far.

I gave him a very good book reference (and the chapter also :grin. What else? Resolve the problem for him?? I mean, I can make a very good coffee as well...

Agree with winnie.

by the way, did you or did you not find unpractical to aply "basic trigonometry" to find the currents on an unbalance system?

if you didnt. I will LOVE to see how do you do it.

 

[mivey]

I could easily inferred that he was talkin about a balance system. Not that he was struggling to understand...

If you could demonstrate a single phase, 20 amp load connected line-neutral with no neutral current, you might convince me. :grin: He started out by trying to take a 20 amp load on a two wire circuit and split it into 10 amps per wire. Seems like he is struggling to me.

I gave him a very good book reference (and the chapter also :grin.

A very good reference. I have it as well.

What else? Resolve the problem for him??

Why not? You live in a beautiful tropical paradise and need to get away from the life of luxury for a little while.

I mean, I can make a very good coffee as well...

I'll take 1 cup, two cream & two sugars while I wait on your demo, please.:grin:

 

[mivey]

by the way, did you or did you not find unpractical to aply "basic trigonometry" to find the currents on an unbalance system?

The basic trig was in reference to Besoeker's example. Your post immediately followed his and I took it as a reply to his train of thought, not as a completely different topic. If I jumbled the two posts: my apologies for the mix-up, and please continue with your train of thought.

 

[mivey]

Substantially lower than my consultancy fees.

Yipes! I was counting on pro bono work. :grin:

add: and collect calls.

 

[Mayimbe]

If you could demonstrate a single phase, 20 amp load connected line-neutral with no neutral current, you might convince me. :grin:

Say you have a 3 phase electric system, with 4 wires. In each phase you have:
(the name of each phase is a, b and c. respectably)

Ia= 20< 0?
Ib= 20< -120?
Ic= 20< 120?

All phases have a diferent load connected. In phase a theres a "cat", in phase b is a "dog" and in phase c theres a bunch of "mouses" connected, all of them standing on the fourth wire. Say that the fourth wire is called "neutral" and is equal to the sum of all phases currents. Then:

In=Ia+Ib+Ic= 0

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

A very good reference. I have it as well.

Why not? You live in a beautiful tropical paradise and need to get away from the life of luxury for a little while.I'll take 1 cup, two cream & two sugars while I wait on your demo, please.:grin:

hahaha well some people lives in beautiful places and some people dont... Thats hows the world has been build.
You seem very confident on that coffee. Ill will recomend you to sit down on a nice couch with a nice tv, and a good laptop. Becuase its going to be a very long waiting.

 

[mivey]

...Then: In=Ia+Ib+Ic= 0

Let me see if I can beat Smart $ to the punch: It's -In
The true vector base formula is Ia + Ib + Ic + In = 0

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

Allowing for two previously unmentioned loads to be added to the scenario, that exactly match the load proposed by the OP: I will say O.K., you created a different scenario where it could happen if they were all well-trained.

hahaha well some people lives in beautiful places and some people dont... Thats hows the world has been build.
You seem very confident on that coffee. Ill will recomend you to sit down on a nice couch with a nice tv, and a good laptop. Becuase its going to be a very long waiting.

I'm guessing I should not hold my breath either. :grin:

 

[Mayimbe]

Let me see if I can beat Smart $ to the punch: It's -In
The true vector base formula is Ia + Ib + Ic + In = 0

??? :-? :-?

How? did he explain how can that possibly happen?

Only if he assumed that the neutral is not a return path for the current. And somehow the current in the neutral flows towards the load and not the source.

I can assume that all the phases currents flows from the load to the source, as well. So it would be -Ia-Ib-Ic=In.


The only things that matter is that we satisfied the Kirchoff current Law.

And I did satisfied it.

I'm guessing I should not hold my breath either.

You should not.

 

[tryinghard]

Where could one find this formula?

Chris, maybe this topic has progressed past this but notice Http://www.mikeholt.com/documents/freestuff/ElectricalFormulas.pdf

 

[mivey]

??? :-? :-?

How? did he explain how can that possibly happen?

Only if he assumed that the neutral is not a return path for the current. And somehow the current in the neutral flows towards the load and not the source.

I can assume that all the phases currents flows from the load to the source, as well. So it would be -Ia-Ib-Ic=In.


The only things that matter is that we satisfied the Kirchoff current Law.

And I did satisfied it.

It is a sign convention preference. It was supposed to be a tongue-in-cheek joke to Smart $ as I repeated his post.

You can state it as the sum of all the currents in must equal the sum of all the currents out.

You can also say that currents in have one sign and currents out have the opposite sign so that the sum of currents equals zero.

It really doesn't matter to me as it works either way. Smart $ likes the sum of currents equals zero.

 

[Mayimbe]

It is a sign convention preference. It was supposed to be a tongue-in-cheek joke to Smart $ as I repeated his post.

I see. I can tell that you began this day with the joke foot as well. So...
FYI
The coffee and the demo will ready tomorrow at first hour

until then

 

[mivey]

I see. I can tell that you began this day with the joke foot as well. So...
FYI
The coffee and the demo will ready tomorrow at first hour

until then

Forget the demo and bring donuts!

joke foot? Never heard that expression. Local phrase?

 

[chris kennedy]

Chris, maybe this topic has progressed past this but notice Http://www.mikeholt.com/documents/freestuff/ElectricalFormulas.pdf

Nice link thanks. (saved) I like the way these threads progress, I follow them closely. A wealth of info. I would also like to thank Visitor for his off Forum help.

 

[Smart $]

It is a sign convention preference. It was supposed to be a tongue-in-cheek joke to Smart $ as I repeated his post.

You can state it as the sum of all the currents in must equal the sum of all the currents out.

You can also say that currents in have one sign and currents out have the opposite sign so that the sum of currents equals zero.

It really doesn't matter to me as it works either way. Smart $ likes the sum of currents equals zero.

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.

 

[iwire]

You engineers can not even answer a simple question.

How does current flow in a circuit?

Completely