Neutral Question

[mbrooke]

I am gonna give you the benefit of the doubt and believe that you are not saying that if there is a voltage potential between two points there will be “ current flow”, I think you mean that the voltage potential must exist for the possibllty of “ current flow” to occur.

Always do- yes- the second one. Current can not flow without voltage.

????
open ckt
touch h-g
touch n-g
is the a difference?
is g/earth considered 0 potential?

Take a volt meter L-N- does it not read 120 volts?


N-G, Unless there is no load, there will be up to a few volts potential due to the voltage drop across the neutral.

But going back- if the neutral has no potential as you said, it could not read 120 volts, correct?

 

[Ingenieur]

interesting
GE Company 1900 description on Edison 3w siystem
https://books.google.com/books?id=E...n conductor positive negative neutral&f=false

Positive +
Negative -
Neutral +-

 

[Ingenieur]

Always do- yes- the second one. Current can not flow without voltage.

Take a volt meter L-N- does it not read 120 volts?

N-G, Unless there is no load, there will be up to a few volts potential due to the voltage drop across the neutral.

But going back- if the neutral has no potential as you said, it could not read 120 volts, correct?

at the n-g bonding jumper you read voltage?

I postulated the neut nomenclature came from the charge state, pos, neg or neut
you said the neut has net charge
you are conflating 2 different things

in a perfect system the neut/gnd cond will have no potential or charge since it is not connected to a source that supplies potential (emf) to drive charge/current
emf = dW/dq work applied per unit charge to 'move' it

in a closed ckt the n or g will return charge driven by the source back to the source
open the ckt and the n goes to a balanced state, no charge delta

 

[jumper]

Well said. Spoken like an engineer. Now I know you have gone completely crazy.

Thanks.

 

[jumper]

interesting
GE Company 1900 description on Edison 3w siystem
https://books.google.com/books?id=E...n conductor positive negative neutral&f=false

Positive +
Negative -
Neutral +-

Good find, I had only made to the Journal of Electricticy, Power, and Gas, 1915 and had not found a definitive answer.

https://books.google.com/books?id=U...ntists in AC circuit analysis neutral&f=false

 

[mbrooke]

interesting
GE Company 1900 description on Edison 3w siystem
https://books.google.com/books?id=E...n conductor positive negative neutral&f=false

Positive +
Negative -
Neutral +-

Thanks

at the n-g bonding jumper you read voltage?

Usually you do, sometimes even with the main disconnected.

I postulated the neut nomenclature came from the charge state, pos, neg or neut
you said the neut has net charge
you are conflating 2 different things

Yes, because I am disagreeing with you consensus.

in a perfect system the neut/gnd cond will have no potential or charge since it is not connected to a source that supplies potential (emf) to drive charge/current
emf = dW/dq work applied per unit charge to 'move' it

Again- I disagree. No potential means no 120 volts L-N.

in a closed ckt the n or g will return charge driven by the source back to the source
open the ckt and the n goes to a balanced state, no charge delta

Even in the balanced state- L1 and L2 have potential between each of them and the neutral.

 

[Ingenieur]

another way of looking at it
junction/node of a pos, a neg and a neut
kirchhoff and conservation of charge
the sum of i (q/t) = 0
no net charge, ie, 'neutral'

 

[Ingenieur]

Usually you do, sometimes even with the main disconnected.

Yes, because I am disagreeing with you consensus.

Again- I disagree. No potential means no 120 volts L-N.

Even in the balanced state- L1 and L2 have potential between each of them and the neutral.

not in a closed system with a 0 Z gnd

you disagree there are 3 states of charge? Pos, Neg and Neut/no net imbalance

the conductors do not produce the potential
remove the source, no net charge, no potential

so?
there is none between n-g

 

[mbrooke]

not in a closed system with a 0 Z gnd

you disagree there are 3 states of charge? Pos, Neg and Neut/no net imbalance

I do not disagree to the 3 states- just what we might apply to a neutral conductor.

the conductors do not produce the potential
remove the source, no net charge, no potential

I think we can all agree to that.

so?
there is none between n-g

There is- I have yet to see a system without voltage drop or no Z on the neutral.

 

[mbrooke]

another way of looking at it
junction/node of a pos, a neg and a neut
kirchhoff and conservation of charge
the sum of i (q/t) = 0
no net charge, ie, 'neutral'

Why not symmetrical components? I would think they might explain it better, after all a neutral is just a point where 2 or 3 separate electrical systems meet.

 

[Ingenieur]

a 3 wire ckt
500 mcm Cu, 1', no measurable v drop
120/240 180deg
1200 Ohm load on each loop
source V1, V2
R1, R2

loop 1
V1 - V1/R1 (R1) = 0
loop 2
V2 - V2/R2 (R2) = 0
where is Vn?

eliminate neut wire
(V1 - V2) - [(V1 - V2) / (R1 + R2)] (R1 + R2) = 0
exactly same result
the neut has no ckt 'potential' if balanced or cond v drop ignored

potential = emf, a conductor does not generate it (well if i is flowing thru it and it is moving thru a field or ac is involved it kind of does, but not the case here lol)

 

[jumper]

It is gonna be a new year and we are all gonna play nice.

Thank you,
Derek

 

[Ingenieur]

I do not disagree to the 3 states- just what we might apply to a neutral conductor.

I think we can all agree to that.

There is- I have yet to see a system without voltage drop or no Z on the neutral.

are you saying a piece of wht wire laying on the floor has a charge or potential?

no there isn't
what you measure are imperfections, not 'potential' in the neut

 

[mbrooke]

a 3 wire ckt
500 mcm Cu, 1', no measurable v drop
120/240 180deg
1200 Ohm load on each loop
source V1, V2
R1, R2

loop 1
V1 - V1/R1 (R1) = 0
loop 2
V2 - V2/R2 (R2) = 0
where is Vn?

eliminate neut wire
(V1 - V2) - [(V1 - V2) / (R1 + R2)] (R1 + R2) = 0
exactly same result
the neut has no ckt 'potential' if balanced or cond v drop ignored

potential = emf, a conductor does not generate it (well if i is flowing thru it and it is moving thru a field or ac is involved it kind of does, but not the case here lol)

For a perfectly balanced load and symmetrical system, yes, cut the neutral and the voltage across the cut will be zero. I mentioned that in post #4:

http://forums.mikeholt.com/showthread.php?t=188742&p=1882246#post1882246


I think we can agree on this concept eye to eye. :thumbsup:

But saying that a neutral is holding no charge, is IMO incorrect.

 

[mbrooke]

are you saying a piece of wht wire laying on the floor has a charge or potential?

no there isn't
what you measure are imperfections, not 'potential' in the neut

If not connected to anything, then yes, no charge.


Potential: a voltage between two points. Since I can measure 120 volts L-N, the neutral has to have potential. At least by definition.

 

[Ingenieur]

Why not symmetrical components? I would think they might explain it better, after all a neutral is just a point where 2 or 3 separate electrical systems meet.

sc's has ABSOLUTELY NOTHING to do with this and would serve no purpose

if conservation of charge/kirchhoff don't do nothing will

a 5 phase unbalanced system neut the net charge = 0
the neut will carry the imbalance i (q/t) but will not have potential to gnd in a perfect system
the potential/emf is the source, the voltage drop is across the load
the neut = 0

 

[Ingenieur]

If not connected to anything, then yes, no charge.


Potential: a voltage between two points. Since I can measure 120 volts L-N, the neutral has to have potential. At least by definition.

wrong

wrong
by definition it does not
V source = sum(Vloads)
the potential is across the source and loads, not the neut

 

[MAC702]

Actually what the OP wants to know to know is why we use the word “neutral” for the conductor.

...

In short, what is the etymology of the word in an electrical context?

Thank you. I did miss that.

 

[Ingenieur]

15 kv triplex shielded cable 1000' feet long
laid on ground
in service, then disconnected, will it have a charge for a period of time?

 

[mbrooke]

sc's has ABSOLUTELY NOTHING to do with this and would serve no purpose

Think zero sequence current for a moment...

if conservation of charge/kirchhoff don't do nothing will

Yes- but the same thing is happening in two or three separate winding- just out of phase to on another.

a 5 phase unbalanced system neut the net charge = 0
the neut will carry the imbalance i (q/t) but will not have potential to gnd in a perfect system
the potential/emf is the source, the voltage drop is across the load
the neut = 0

In a perfect system with a zero Z noodle- come reality a neutral carrying load will always measure voltage to ground because it will always have impedance to some degree or another. Granted this concept is drifting away from the topic at hand- but you used it as an example to support zero charge which I disagree with.