The neutral and my understanding.

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Chrisasks

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Knoxville, TN
This is my first post, and I've heard there are some on here with great wisdom!

I am in my fourth year of commercial, and am trying to learn all I can on both the theory side and install side.

Today's question: I've been studying transformers and neutrals and bonding.

I would love to get a greater understanding on the flow. thinking in terms of wye, I get that power is stepped down, three legs of 120 happen and a neutral is tapped at a point in the coils where voltage potential is zero. I also understand that in most cases, this zero potential tap is bonded to the ground at the transformer to bring the surrounding area up to that zero voltage potential(correct?). What's more is that it's known that the first means of disconnect bonds neutra bus to ground bus to create a safety path, then are kept separate from there forward, and that the ground should not interact with the power after that.

So As as power flows from let's say phase "A" through a 277v 20ampere device and the unbalanced load returns through the neutral (no other loads connected for simplicity) all the way to the neutral tap on the transformer, where does the flow stop?

Ive read a lot that says it goes to ground and that's it, done and I have trouble thinking that is sufficient as there would be extreme electrolysis and arcing and such as the ground's electrolytes were consumed.

Lets say the whole system was never bonded to ground and we were in a perfect environment where the load was isolated by insulated covers and such so that we could not get shocked and be ok, would the the neutral behave similarly?

Thanks for your time to all of those involved.
 

iwire

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Lets say the whole system was never bonded to ground and we were in a perfect environment where the load was isolated by insulated covers and such so that we could not get shocked and be ok, would the the neutral behave similarly?

Bonding and grounding are not needed for normal circuit operation.

The neutral would be above or below dirt (earth) potential.

The only immediate shock hazard would be contact with things like the screw shell of a lamp and earth.
 

augie47

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Welcome to the Forum.
I'll give it a shot.....
Your Understanding of the bonding, etc. at the transformer is good.
As far as current flow, in a normally operating system the current would simply flow in a circle, as it were, from the phase back to the neutral (or an opposite phase)
The grounding comes in to establish a reference and as a safety means,
The current is always trying to complete that circle, and if you become a part of that path, the current will flow through you.
The equipment ground and bonding provides a path or the current to return safely to the source (transformer). Ina fault situation, the current would flow back through the equipment ground, through the bond to neutral and cause the overcurrent device to open.

As to the second part of your question, if there was no bond the system would operate normally. Then bond is there to provide a path for the current to flow in the event of a fault to ground so the overcurrent device can open.

Others may explain it better but thats a start,

(sorry, Iwire, I was wearing out my fingers as you answers in a better manner)
 

roger

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I would add, think of a ship or airplane, unless they brought along a bucket of dirt they are not connected to earth and their electrical systems work fine.

Roger
 

roger

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neutral tap at transformer---->>>?
That's it, it has completed it's path.

When reading or hearing anybody say electricity seeks earth, the article or person is quoting an eons old MYTH

Roger
 

Chrisasks

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Location
Knoxville, TN
So the electrons just sit still? That confuses the crap outta me. That means there's no loop for flow. It would create a crapton of electrons puddling together.


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roger

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So the electrons just sit still? That confuses the crap outta me. That means there's no loop for flow. It would create a crapton of electrons puddling together.


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I agree with Bob, I don't understand what you are saying. For this conversation we'll say the electron movement starts (leaves) on A phase goes to the load and heads back home on the "neutral conductor" there is a loop. For simplicity look at your flashlight, when you hit the switch the current leaves one terminal and returns on the other.

Roger
 

mivey

Senior Member
So the electrons just sit still? That confuses the crap outta me. That means there's no loop for flow. It would create a crapton of electrons puddling together.


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The transformer acts as a charge pump. In the case of copper wire, the electrons carry the charge. For part of the cycle, the charge leaves terminal "A", down the ungrounded conductor towards the load, through the load, back towards the transformer on the grounded conductor, to the "N" terminal, then through the transformer winding back to terminal "A". There is the loop for a 277-only load.

For mixed loads, the return route may be through a different ungrounded conductor, through a different winding back to the "N" terminal, then through the "original" winding back to the "A" terminal.

The energy always flows towards the load. The electrons do not carry the energy but create part of the medium through which the energy travels. The moving charges (current) create the magnetic field and the separated charges (voltage) create the electric field. The energy travels in the combined electro-magnetic field.
 

mivey

Senior Member
I agree with Bob, I don't understand what you are saying. For this conversation we'll say the electron movement starts (leaves) on A phase goes to the load and heads back home on the "neutral conductor" there is a loop. For simplicity look at your flashlight, when you hit the switch the current leaves one terminal and returns on the other.

Roger
I think he would ponder the charge flow inside the battery from the "-" to the "+" terminal which would completely close the loop. Similarly, he was not aware of the current through the transformer winding from "N" to "A" which closes the loop.
 
thinking in terms of wye, I get that power is stepped down, three legs of 120 happen and a neutral is tapped at a point in the coils where voltage potential is zero.

Just a minor correction here. There isnt a magical place where "voltage is zero." We can tap a transformer winding anywhere and make that a grounded conductor, or even take a phase and ground it making a grounded conductor. In practice, there are only a few different winding configurations that are practical for consistency and symmetry. The Wye connection is one of them. The Wye point works well to use as a grounded conductor because it is symmetrical/equal to the three phases. Because of this, it is called a neutral conductor, a special kind of grounded conductor.

I think Mivey probably answered you question, but think of the winding of the transformer as a reservoir of water. IF you had a pump circulating water molecules around a loop back to the reservoir, they return to the source and can get reused, much like the electrons do to the source winding. On the macro scale, no part of the circuit is getting stripped of electrons or electrons built up, they are just moving like a train around a circular track.
 

Chrisasks

Member
Location
Knoxville, TN
The transformer acts as a charge pump. In the case of copper wire, the electrons carry the charge. For part of the cycle, the charge leaves terminal "A", down the ungrounded conductor towards the load, through the load, back towards the transformer on the grounded conductor, to the "N" terminal, then through the transformer winding back to terminal "A". There is the loop for a 277-only load.

For mixed loads, the return route may be through a different ungrounded conductor, through a different winding back to the "N" terminal, then through the "original" winding back to the "A" terminal.

The energy always flows towards the load. The electrons do not carry the energy but create part of the medium through which the energy travels. The moving charges (current) create the magnetic field and the separated charges (voltage) create the electric field. The energy travels in the combined electro-magnetic field.

Understood. That's the solution to what I was seeking! So the "extra" or unbalanced electrons/charge gets thrown back in the loop, right?


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mivey

Senior Member
Understood. That's the solution to what I was seeking! So the "extra" or unbalanced electrons/charge gets thrown back in the loop, right?


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No extras. Think of the charge loop like a belt on a motor/fan assembly. No extra rubber gets added when the motor causes the fan blade to turn. What gets added is energy.

While speaking of the belt, the rubber at the motor does not have to reach the fan before the blade turns because the energy travels near light speed through the medium. The belt is the medium through which the energy travels.

But if by thrown back you mean as one electron leaves one side of terminal "A" then another enters on the other side then, yes.
 

iwire

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While speaking of the belt, the rubber at the motor does not have to reach the fan before the blade turns because the energy travels near light speed through the medium. The belt is the medium through which the energy travels.

A way I saw it explained and helped me understand the nature of electrcity was this.

Imagine a tube from Boston to Hollywood the tube is just big enough for a single row of ping pong balls to fit in a perfect line.

Now move a ball into the tube in Boston and one pops out in Hollywood at the same instant even though no particular ball had to move fast at all.
 

mivey

Senior Member
A way I saw it explained and helped me understand the nature of electrcity was this.

Imagine a tube from Boston to Hollywood the tube is just big enough for a single row of ping pong balls to fit in a perfect line.

Now move a ball into the tube in Boston and one pops out in Hollywood at the same instant even though no particular ball had to move fast at all.
A good illustration for a start and works ok for DC except that it gives visions of a coal-car type delivery of energy. There is a similar issue with my pulley example with the motor/fan turning only one direction.

With AC, something like a rope saw gives a better picture of the oscillatory nature where the mechanism/material just wiggles back and forth and no material gets replaced at one end of the pipeline. It provides a better lead-in to the physics discussion that we are adding energy to the system and not physical electrons or whatever.
 

iwire

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Location
Massachusetts
A good illustration for a start and works ok for DC except that it gives visions of a coal-car type delivery of energy. There is a similar issue with my pulley example with the motor/fan turning only one direction.

With AC, something like a rope saw gives a better picture of the oscillatory nature where the mechanism/material just wiggles back and forth and no material gets replaced at one end of the pipeline. It provides a better lead-in to the physics discussion that we are adding energy to the system and not physical electrons or whatever.

To each their own, I see it as applicable of AC and DC.

Make it me in Boston, Randy in Hollyweird and each of us taking turns putting the ball back in the tube.

No analogy is perfect, it's just that particular one worked for me, it made the concept of instant without the need of speed clear for me. It might just confuse someone else.
 

mivey

Senior Member
To each their own, I see it as applicable of AC and DC.

Make it me in Boston, Randy in Hollyweird and each of us taking turns putting the ball back in the tube.

No analogy is perfect, it's just that particular one worked for me, it made the concept of instant without the need of speed clear for me. It might just confuse someone else.
If you get the return path worked out with Randy it improves the analogy.
 
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