Neutral and its Balanced load

[ronaldrc]

I call it a grounded conductor. After reading through all this I came
to realize that it may be understandable for some who have been in the trade for a time
but the concepts and the terms make it difficult to explain to our students. And I think
that this is your concern.

So I went looking....and found this.

When a 'neutral' isn't a neutral

Good article

The only thing I see I disagree with is to be a neutral it says anything tapped midpoint.
It doesn't mention polarity. To operate like the true Edison neutral and to balance out the
polarity has to be opposite at the neutral point to balance. In other words at the neutral
point you need to have a positive and a negative. Not two positives or two negatives.

In the real world of working with wye three phase and the Edison single phase this is
always the case so Electricians don't need to worry about that.

But in the Electronics design this might not be the case so the designers would need to
watch for polarity if he wants the circuit to balance for some reason. .

 

[ronaldrc]

Why ground the Neutral

Why ground the Neutral

Here is a link to a analogy to a balance circuit using batteries as an example.


http://home.comcast.net/~ronaldrc/wsb/ax.htm


Why ground the Neutral

This is just my own opinion and it might change.


One more thing about our true Edison neutral conductor.That will null with equal loads
on both sides.

I know everyone has figure this one out by now. But if you are wondering why the
neutral is used for the grounding point of our system.

Consider If line #1 or #2 where used as the grounding point to the earth ground.

The main point of grounding is to operate the trip function of the breaker supplying
the branch circuit upon a short circuit or fault. Therefore tripping before the current in the
conductor causes the insulation,appliance Etc. to burst out into a flames and burn your
house down.

The neutral voltage is the lesser dangerous of the lines if used as ground, instead of
the 240 volt to ground if we would have used Line #1 or line #2 for a ground.

Less say we used line #1 as the ground , now if the neutral contacts a ground it will
kick the breaker and do pretty well the same physical damage to materials and people that
it does now.

But if line #2 contacts a ground it will kick the breaker and do a lot more physical
damage to materials and people than 120 volts would.

One more thing a shock from 120 volts is a less likely to be fatal than a shock from 240
volts. And believe me hurts a whole lot less I know this first hand.

 

[76nemo]

Why would one say it is unfair to say the grounded carried the unbalance in 2+ wire systems?

 

[cadpoint]

One more thing about our true Edison neutral conductor.That will null with equal loads
on both sides.

I know everyone has figure this one out by now. But if you are wondering why the
neutral is used for the grounding point of our system.

Frankly I had to go look up an Edison neutral, note the neutral is linked right to the ground (symbol). diagram

It doesn't matter if your draw a single line of AC or DC with a device and the continuation of the circuit conductor it is either the Neutral or Grounded, respectfully, and thats already been said. It it one in the same in both systems, Yes ...

 

[ronaldrc]

Cadpoint

When I first seen that sine wave I thought it was a joke.
Our neutral sine waves now probably do look that bad

Then I seen click to see next page

 

[quogueelectric]

Mivey Years ago when I helped an Electrician change out a service I happen to get a screw driver bridged across the neutral and equipment grounding bar in a sub panel and it sparked like a welder.[/b]

Many electricians would not understand why this happens.

 

[ronaldrc]

Did I say it was similar to a low voltage AC welder? it did

 

[ronaldrc]

I need to go to bed ,now I can't even read my own writing, you know what I mean.

 

[mivey]

I call it a grounded conductor. After reading through all this I came to realize that it may be understandable for some who have been in the trade for a time but the concepts and the terms make it difficult to explain to our students. And I think that this is your concern.

So I went looking....and found this.

When a 'neutral' isn't a neutral

It was a little long winded and out of date. Too much outside the topic of a simple definition of neutral.

It would be much simpler to refer to the definitions of neutral and neutral point in NEC 2008.

 

[iwire]

Only problem I have with Wikepedia is anyone and their uncle can register, log in, and change the articles.

You don't even have to register, just stop in and click any edit button you see and then go nuts.

Yeah I am sure major misstatements would get picked up on but .........

 

[dicklaxt]

Heres the way I see it, the so called neutral or grounded conductor always has an equivalent current flow as the line conductor in a 2 wire circuit. On the other hand a 3 wire 120/240 with 2 line conductors and a grounded/neutral conductor is connected thus,,,,, equal loads from L1 to neutral and L2 to neutral, this is 2-120volt equal loads wired in series and no current flows on the neutral, the source sees it as a 240v load and current flows on L1 and L2. Now if one of the 120 loads were to have a different load value then the difference in the current draw would be seen on the neutral as the unbalance.

I think this is right but somebody jump in and correct me if thats not right.

dick

 

[dicklaxt]

Another thought might be if a third load were added to from either L1 or L2 thern that loads current would appear on the neutral as well or am I full of BS on all of this ?

I studied these circuits in 1954 and a refresher in 1962,its been a while.


dick

 

[ronaldrc]

This is the best I can do to explain the neutral

It is very simple if you really want to understand it.

Click on the link below

http://home.comcast.net/~ronaldrc/wsb/The_Edison_Neutral.html

 

[dicklaxt]

agreed and when the IR drop across both #1&2 loads are 120 and the neutral is common then current flow is on line conductors only.

I'm glad you posted that diagram which confirms my memory is still okay while other things have quite working.

LOL

dick

 

[ronaldrc]

Dick

Thanks, Know the feeling, I reached that point years ago.

 

[dicklaxt]

Hey Ronald

Out of curiousity ,,,,,,,,,I'm having trouble with your Avatar circuit.

I'm seeing a seal in via the contact assuming thats a motor starter aux contact when the jog button is hit.

When the start button is hit I see a contact race between the aux contact and the NC switch contact in the seal in circuit.

How about a full description of function.I'm missing siomething
dick

 

[ronaldrc]

Dick


I wanted to show a jog without a separate jog relay or contactor.


I know about the race between the button and seal contact and in some
equipment or starters has caused injuries.

If use in equipment where people are apt to get injured this circuit shouldn't be used.

It needs a separate jog relay to be safe.

 

[dicklaxt]

Duh,,,,,,,,,,, if I change names on the jog and start buttons it works ,I'll go back to sleep now

dick

 

[ronaldrc]

Hi Dick

No you where right about the Jog Avatar.

In some Magnetic starters where the mechandical parts are badly worn the aux, or seal contact stays made or closed before the jog button closed contact has a chance to drop out, or open and machine continues to run.

This is the reason if you have personnel around the equipment that can be injured you need to use a jog relay.

 

[dicklaxt]

Ronald I sent you a circuit .look at you PM

dick