Homework 3 phase to single phase

[Baker1988]

Hi every one i was just looking for a bit of help i have been given some home work from college that i am not sure on, We have just started learning about 3 phase so not very good at it yet but i have been given home work i have to draw a circuit diagram and a wiring diagram for a balanced 3 phase motor going into a 3 phase isolator (i dont have to draw the motor i just have to start from the isolator) which then will go into a 3 phase board i understand that but the thing is i have to go from the 3 phase board to 2 seperate single phase consumer units (like a domestic consumer unit) the problem i have got is if it is a balanced 3 phase motor supply there will not be a neutral connector going into the 3 phase isolator or board so when i go to wiring the single phase consumer unit will i still have to put a neutral in as the neutral will just end up stopping in the single phase board and wont go anty where else as the 3 phase is balance i know that in a single phase circuit you need the neutral as the return path i just wasnt sure if it needed it when fed from a balanced 3 phase motor


any help to clarify this or even a link to a good web page would help thank you

 

[Knobhead]

Print the question out word for word, I can't make sense of you're description.

 

[Baker1988]

It says draw a circuit / wiring diagram for a 3 phase balanced circuit feeding 2 single phase consumer units. That's the question I was just asking if the 3 phase is balanced they will not be a neutral so on the single phase do I put in a neutral as there is no neutral in the 3 phase

 

[AndyL]

Are you sure thats word for word, cos it still dont make sense, feeding 2 single phase CUs will never result in a balanced load on a 3 phase circuit because you are not using all of the phases

 

[Knobhead]

So where did the motor come from in you're fist post. Get the question clarified.
I'm sorry but I for one won't guess what is required.

 

[AndyL]

Just re read Op, i think this is a two part question, draw the 3ph motor supply from the 3 ph CU, this part will be balanced. Then draw 2 single phase distribution circuits from the 3ph CU, one going to each of the 1ph CUs

 

[oldtimer]

Ok we get a lot of this and there is 2 ways of thinking one side gives you the answer and the other tells you to sort it out yourself but me why dont you print the question attached your schematic and we will see where we go from here . Dont get me wrong nobody is trying toi be smart but you need to learn how to get to the answer yes you can google it but but thats not going to help you to learn

 

[Silly Sausage]

It says draw a circuit / wiring diagram for a 3 phase balanced circuit feeding 2 single phase consumer units. That's the question I was just asking if the 3 phase is balanced they will not be a neutral so on the single phase do I put in a neutral as there is no neutral in the 3 phase

You can still physically have the Neutral in a balanced 3 phase system, it's just that there will be no current flowing in it.

 

[Deservices]

I agree a balanced 3 phase board should still have a neutral in it. It's just that the motor doesn't need a neutral to work as its a 3 phase motor. So you would just have a brown(phase1), black(phase2), grey(phase3),earth going to the motor. And a brown(live from phase1) and blue neutral,green/yellow(earth) feeding CU 1. Brown(live from phase 2) blue(neutral) and green/yellow feeding CU 2. Like everyone has said, it's best to upload a picture of the question, as everyone will interpret it different.

 

[snowhead]

So what's the motor balanced on,, A fence?

 

[Deservices]

So what's the motor balanced on,, A fence?

All motors are balanced generally other wise it would cause problems with blowing fuses. Also a unbalanced motor wouldn't get up to its optimal speed. Even vibrators have a balanced motor attached.

 

[Knobhead]

I agree a balanced 3 phase board should still have a neutral in it.

Why ? ?

 

[Knobhead]

All motors are balanced generally other wise it would cause problems with blowing fuses. Also a unbalanced motor wouldn't get up to its optimal speed. Even vibrators have a balanced motor attached.

What on earth are you talking about?

 

[1shortcircuit]

Hi every one i was just looking for a bit of help i have been given some home work from college that i am not sure on, We have just started learning about 3 phase so not very good at it yet but i have been given home work i have to draw a circuit diagram and a wiring diagram for a balanced 3 phase motor going into a 3 phase isolator (i dont have to draw the motor i just have to start from the isolator) which then will go into a 3 phase board i understand that but the thing is i have to go from the 3 phase board to 2 seperate single phase consumer units (like a domestic consumer unit) the problem i have got is if it is a balanced 3 phase motor supply there will not be a neutral connector going into the 3 phase isolator or board so when i go to wiring the single phase consumer unit will i still have to put a neutral in as the neutral will just end up stopping in the single phase board and wont go anty where else as the 3 phase is balance i know that in a single phase circuit you need the neutral as the return path i just wasnt sure if it needed it when fed from a balanced 3 phase motor


any help to clarify this or even a link to a good web page would help thank you

Have a look through previous posts made by each poster in this thread

You will notice pretty soon that there is most definitely a person posting here that will know the answer once you have attached the question "Word for Word" and they will also be able to prompt and point you in the direction needed to help you learn how to answer the question.


One thing I believe is, you can present someone who knows everything about everything a question and they can still get it wrong. The reason? They have not read the question as it was intended or they have missed the key word. This is why it needs to be seen word for word:thumbsup

 

[Deservices]

Why ? ?

Well I work in a factory that has 3 phase boards everywhere and all have neutrals in them. The only time it may not if its a sub board for use with just 3 phase motors that don't need a neutral.

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What on earth are you talking about?

Is it not obvious?