un-balanced three phase system

[shakerbess]

hi i was hoping to get some help with a question please.

why does the current flow in the neutral when the three phase system is un-balanced?

is it to do with the fact when you have an unbalance between the phases the difference of current between the phases that causes excess current will then flow into the neutral?

 

[shakerbess]

neutral

please can some body explain why in an unbalanced three phase system the current will flow in the neutral?

 

[Rockingit]

OK. The only real way of getting your head into and around this is to go right back to the start: How is electricity generated, what actually happens when the rotor starts spinning inside the coils?

 

[snowhead]

Re: neutral

please can some body explain why in an unbalanced three phase system the current will flow in the neutral?

Can you explain why in a balanced system there is no neutral current?
Then the answer to your question might be apparent.

 

[HandySparks]

Picture the extreme case of unbalance where there is no load on two of the phases. You'll then have the same situation as a single phase supply with equal current in the line and neutral. Now if you increase the load on the other two phases, the neutral current will fall (to zero if it's fully balanced).

 

[HandySparks]

Another word of advice. Don't post the same question twice. It just annoys people and causes work merging them.

 

[HandySparks]

And another thing. How can you be an approved electrician and a trainee at the same time?

 

[Marvo]

2 x similar threads merged.

 

[HandySparks]

And if you're an approved electrician, why don't you 'get' the fundamentals of three phase?

 

[Knobhead]

To calculate the neutral

I[SUB]n[/SUB] = √((I[SUB]a[/SUB]²+I[SUB]b[/SUB]²+I[SUB]c[/SUB]²)-((I[SUB]a[/SUB]*I[SUB]b[/SUB])+(I[SUB]a[/SUB]*I[SUB]c[/SUB])+(I[SUB]b[/SUB]*I[SUB]c[/SUB])))

 

[shakerbess]

And another thing. How can you be an approved electrician and a trainee at the same time?

firstly thankyou for taking time to reply

the approved and trainee who gives a hoot lol just me i suppose not very good with computers i posted the question then realized posted it in the wrong place mate i did not think ppl would get so excited with silly mistakes lol

like i said thanks for the reply pal

 

[shakerbess]

Re: neutral

yes im sorted thanks found my answer thanks for the hint mate

 

[shakerbess]

lol if i ask a question do i have to also justify if im an approved sparky lol
another think mate don't bother answering a question if it seems to upset you what is the point of the forum if you start to question if people are approved or not i reckon you should put the sheriff badge away and remember the forum was designed to help folk not to have you sit there and judge ppl lol
im sorry i posted the question did not think id upset superstar like lol

 

[ImpededLoop]

And if you're an approved electrician, why don't you 'get' the fundamentals of three phase?

Easy tiger, you've just added four posts to your total!

It's hard to answer the OP without a diagram, but If you think of a three phase motor that has no neutral, all phases are balanced as there are three identical windings. If one of the three phases was a greater load than the other two, the current has to return via the neutral.

 

[shakerbess]

whats that got to do with me being a spark lol i asked a question if you can answer cool if not what the sillyness has me being a spark got to do with anything lol maybe i should know its stuff i did years ago but life is such some times you forget the most basic but if you read the question i asked i had given the answer to my question too lol
please tell me do folk like you sit on these forums have nothing useful to add and talk garbage lol

 

[shakerbess]

lol thanks mate i found what i was looking for cheers pal for reply

 

[ImpededLoop]

whats that got to do with me being a spark lol i asked a question if you can answer cool if not what the sillyness has me being a spark got to do with anything lol maybe i should know its stuff i did years ago but life is such some times you forget the most basic but if you read the question i asked i had given the answer to my question too lol
please tell me do folk like you sit on these forums have nothing useful to add and talk garbage lol

Calm down, my first paragraph was in reply to Handysparks who had given four near consecutive replies.

I think you've jumped as my reply was posted a few seconds after yours!

 

[Knobhead]

And another thing. How can you be an approved electrician and a trainee at the same time?

I think the OP needs to give an explanation.

 

[Guest55]

i love to read garbage , seems like im in the right place !

;-)

 

[HandySparks]

I think the OP needs to give an explanation.

Exactly Tony. I'm just totally confused about what level of understanding the OP is at.