what does a neutral do

[m4fiaafg]

this question may seem basic, but none the none the less, please can some one explain what is the role of the neutral conductor, my questions are.

is the current in the phase conductor and neutral conductor the same? because if they werent then the rcd would start tripping?

does the neutral conductor carry any voltage. if not, what pushes the current back to the neutral point transformer?.

why dont you get shocked when you touch a neutral conductor, when it carries current, is this because there is 0 volts hench no push?

thank you, i know its quite basic, but its one of those things that i couldent really get my head round in collegee

please can you explain in as much detail as possible thanks

 

[Des 56]

The neutral conductor
Now I hope you get a few replies,because everyone will have their own way of trying to explain

My own effort would begin with erxplaining what it is rather than what it does

When a 3 phase supply is generated at the power station.the transmission of the electricity is via step up transformers to distribute it and step down transformers to deliver it locally at useable voltages

At a local level the 3 phases are connected to a step down transformer
The outgoing or secondary side of that transformer will be connected in a star formation
Each phase uses the other two to return current through the supply circuit

When connected in this star formation the point where the ends of each winding are connected together is called the star point
At that star point the 3 phases equal each other out,so there is no potential difference
This star point is also connected to the general mass of earth

If you take the supply off one of the phas windings and another off the star point then there will be a potential difference and connecing a load will allow current to flow

So if you take a phase to an house and also a cable from the star point,then you will have a potential difference at that house
The cable you take from the star point is called a neutral
It is neutral with regard to all the phases

Question 1 is yes they are carrying equal current ,if they weren't then as you say the RCD would trip

Voltage is apparant when there is a potential difference between conductors
The conductor with the high potential will attempt to push current through another that is connected to it which has a lower potential

So if a phase which has a high potential is connected through a load which is then connected to the low potential neutral then current will flow

If you touch that neutral you will not get a shock unless a circuit is completed by yourself by also touching a phase conductor which would give the potential difference to allow current flow

The neutral conductor may have a small potential difference to earth,but this is avoided by connecting it to earth along its run from the supply transformer It would not be enough to cause a shock to someone touching both
As you say no push (better to use the words potential difference)l

 

[xraytek]

The neutral conductor
Now I hope you get a few replies,because everyone will have their own way of trying to explain

Oh if you insist!

If you think of a single phase supply as being like a battery, then imagine connecting a bulb between the positive side of the battery and an earth rod in the ground.
The bulb will not light up because the circuit back to the battery is not complete.

If the negative side of the battery was connected to earth then the bulb will light up (if voltage was high enough to pass the current through the earth)

If you connect the bulb between the negative side of the battery and earth then it will not light up because there is no potential difference.

NEXT...

 

[c.boy]

Oh if you insist!

If you think of a single phase supply as being like a battery, then imagine connecting a bulb between the positive side of the battery and an earth rod in the ground.
The bulb will not light up because the circuit back to the battery is not complete.

If the negative side of the battery was connected to earth then the bulb will light up (if voltage was high enough to pass the current through the earth)

If you connect the bulb between the negative side of the battery and earth then it will not light up because there is no potential difference.

NEXT... [/quotea


always 1 fanny!!!!!!

 

[m4fiaafg]

The neutral conductor
Now I hope you get a few replies,because everyone will have their own way of trying to explain

My own effort would begin with erxplaining what it is rather than what it does

When a 3 phase supply is generated at the power station.the transmission of the electricity is via step up transformers to distribute it and step down transformers to deliver it locally at useable voltages

At a local level the 3 phases are connected to a step down transformer
The outgoing or secondary side of that transformer will be connected in a star formation
Each phase uses the other two to return current through the supply circuit

When connected in this star formation the point where the ends of each winding are connected together is called the star point
At that star point the 3 phases equal each other out,so there is no potential difference
This star point is also connected to the general mass of earth

If you take the supply off one of the phas windings and another off the star point then there will be a potential difference and connecing a load will allow current to flow

So if you take a phase to an house and also a cable from the star point,then you will have a potential difference at that house
The cable you take from the star point is called a neutral
It is neutral with regard to all the phases

Question 1 is yes they are carrying equal current ,if they weren't then as you say the RCD would trip

Voltage is apparant when there is a potential difference between conductors
The conductor with the high potential will attempt to push current through another that is connected to it which has a lower potential

So if a phase which has a high potential is connected through a load which is then connected to the low potential neutral then current will flow

If you touch that neutral you will not get a shock unless a circuit is completed by yourself by also touching a phase conductor which would give the potential difference to allow current flow

The neutral conductor may have a small potential difference to earth,but this is avoided by connecting it to earth along its run from the supply transformer It would not be enough to cause a shock to someone touching both
As you say no push (better to use the words potential difference)l

thNK U for your time and effort, much appreciated

 

[Spudnik]

Great post there Des.

 

[chocolate]

Try this different point of view . . .

Current flows from the supply ( via the phase / line conductor ) to some accessory ( eg. light bulb ), and then flows back to the supply via the neutral conductor.

The current flowing to ythe lamp, and away from the lamp are the same. Hence RCD not tripping.

Current is simply a means of moving electrical energy around a circuit. The supply takes energy ( using the flow of current ) to the lamp. At the lamp, the energy is turned into heat and light. The current leaves the lamp having the energy taken away from it.

This provides a complete ( no gaps ) circuit.

HOWEVER. If you were fool enough to disconnect the Neutral ( for that circuit ) at the consumer unit, the light would now not light. A gap has appeared. No current can flow. The light doesn't light as no energy is being delivered to the lamp.

BUT if you touched the Neutral wire, you could get a serious shock !!!!!

Now, you are providing the link to fill the gap in the circuit, needed to make it work. Current can now flow again - resulting in energy being delivered to the lamp and to YOU.

 

[RETIREDSPARKY]

Well done all, but what about the electron flow which must flow from nuetral to positive before you can get current flow.

 

[Darkwood]

Well done all, but what about the electron flow which must flow from nuetral to positive before you can get current flow.

Be carerful here with how you word this as electrons tend to just vibrate in a.c. and dont flow as is the popular concept, where as dc does have a negative to positive flow but in the region of mm per minute depending on the current and voltage.

The propogation of the electromagnetic field is what is actually flowing around about 96% the speed of light in copper conductors.

I know its all a bit quantumn but hope its of interest and from what i hear they still teach students that electrons do the flowing, just to make it easier to picture i assume.

 

[Monkeyblaine]

The neutral conductor
Now I hope you get a few replies,because everyone will have their own way of trying to explain

My own effort would begin with erxplaining what it is rather than what it does

When a 3 phase supply is generated at the power station.the transmission of the electricity is via step up transformers to distribute it and step down transformers to deliver it locally at useable voltages

At a local level the 3 phases are connected to a step down transformer
The outgoing or secondary side of that transformer will be connected in a star formation
Each phase uses the other two to return current through the supply circuit

When connected in this star formation the point where the ends of each winding are connected together is called the star point
At that star point the 3 phases equal each other out,so there is no potential difference
This star point is also connected to the general mass of earth

If you take the supply off one of the phas windings and another off the star point then there will be a potential difference and connecing a load will allow current to flow

So if you take a phase to an house and also a cable from the star point,then you will have a potential difference at that house
The cable you take from the star point is called a neutral
It is neutral with regard to all the phases

Question 1 is yes they are carrying equal current ,if they weren't then as you say the RCD would trip

Voltage is apparant when there is a potential difference between conductors
The conductor with the high potential will attempt to push current through another that is connected to it which has a lower potential

So if a phase which has a high potential is connected through a load which is then connected to the low potential neutral then current will flow

If you touch that neutral you will not get a shock unless a circuit is completed by yourself by also touching a phase conductor which would give the potential difference to allow current flow

The neutral conductor may have a small potential difference to earth,but this is avoided by connecting it to earth along its run from the supply transformer It would not be enough to cause a shock to someone touching both
As you say no push (better to use the words potential difference)l

I also struggle with the concept of Neutral current flow and just AC in general.

I understand that current flows in both direction 50 times a second, assuming your supply is at 50hz, and I also understand that in a positive half cycle the line conductor is at 230v and in a negative half cycle the line is at -230v, what I find hard to grasp is what is pushing the current flow through the neutral on the negative side of the wave seeing as the neutral conductor always remains at 0v. Would I be correct in saying that when the wave dips below 0v i.e -230 is that the force that pushes it back through the neutral, as opposed to the line conductor which contains the force which pushes the current the neutral seems to have its push from elsewhere.

Yeah so my main question is where is the neutral receiving its push from? its always at 0V... Im sorry to go on about this but I have a brain that wants to know everything yet doesn't catch on that quickly... its a curse!

 

[ackbarthestar]

try this one, as Darkwood has just indicated

Electrical current flow is an electromagnetic energy wave traveling just under the speed of light with a carrier frequency of 50Hz.
The return path still carries the energy but this is now referenced to earth potential so there will be no potential difference between you and the neutral return path

 

[lauriehurman]

I also struggle with the concept of Neutral current flow and just AC in general.
Yeah so my main question is where is the neutral receiving its push from?


So why not think about as a pull?
If you think of the neutral as being at zero and the line being at -230 then think of the line as pulling the electron (or field) flow rather than pushing it.

Laurie

 

[Darkwood]

try this one, as Darkwood has just indicated

Check out the date stamp on my post lol its 3yrs old, you had me confused a bit then saying i just indicated it lol

 

[Knobhead]

Monkey, will you please stop winding people up.

 

[leonard290]

the neutral is classed as a live conductor even though it is at zero potential.In a balanced 3 phase circuit which means current flow is equal in the brown/grey/black phases the star point(nuetral} will be zero.You can get a shock off the neutral if the 3phase is not balanced ie; 10amps in brown 30amps in grey 90amps in black.potentially the neutral could rise as high as the phase voltage so be careful,i wasnt when working in a marina,i found out later that over the years all the add on circuits caused the unbalance of th 3phase supply