3phase volt drop.

[Simonslimline]

This is one of a weekly question by sparks magazine posted on Facebook to win free tools each week. Everyone has answered B. 8Volts. I am not sure this is correct. Please could anyone help me with this. I have posted it up in here rather than just the trainee section so more people will see it. Not bothered about the prize. I just have a feeling that 8volts is wrong, but would happily be corrected on this. Thanks.

To comply with IEE Wiring Regulations the voltage drop on a three phase 400v Circuit should not exceed:
a) 4v
b) 8v
c) 20v
d) 32v

 

[trev]

No!
I'm talking about ****!

 

[Zebra Stripe]

Oh....a concubine? why didnt you say.:shocked3:

 

[shanky887614]

I said it was a sweary word man!
Thas aanly one wi C man!

guessing he is a berk/Jeremy hunt then

 

[Zebra Stripe]

Gotcha, Jermey Hunt is an f"ing ........punani

 

[D Skelton]

If you look at larger installations with lighting fed by overhead busbar trunking most of them are 3 phase.

Are you sure? I've only ever worked on and installed busbar lighting power track with a distributed neutral, therefore the lighting isn't three phase even though there are three phases housed within.

I've yet to come across 400V lighting.

 

[Simonslimline]

Sparks magazine will announce the answer/winner on thursday so i will post up what they say. If it is 8v i am going to message them to ask where they got the answer from.

 

[Zebra Stripe]

As its a C&G question you'll never find out what their correct answer was or is or could be in a negative/positive sort of way, but good luck.

 

[Simonslimline]

As its a C&G question you'll never find out what their correct answer was or is or could be in a negative/positive sort of way, but good luck.

we just sat the 309 science and principles written exam at college. A question came up about neutral current in a 3 phase 4 wire system. the loads were L1 40amps, L2 30amps, L3 20amps. the answer sheet said there was no neutral current. I did the formula and worked out the answer being 17.32A. I didnt get marks for it. I told them they were wrong. They realised and gave me the marks.

 

[Zebra Stripe]

Probably loads of questions in all exams which are quite frankly either worded incorrectly or marked wrong.

IMO exams are not a very good way to judge someones real understanding of a subject or for a student to realy grasp and understand something. You will forget most of the stuff you revise in a very short period of time. Written assement, where one researches the subject and writes a report or paper is by far a better way for a student to understand and gain lasting knowledge.

 

[D Skelton]

we just sat the 309 science and principles written exam at college. A question came up about neutral current in a 3 phase 4 wire system. the loads were L1 40amps, L2 30amps, L3 20amps. the answer sheet said there was no neutral current. I did the formula and worked out the answer being 17.32A. I didnt get marks for it. I told them they were wrong. They realised and gave me the marks.

Without information as to the nature of those loads, no answer can be gien. If they were all single phase resistive loads the neutral current would be 40A. If there was a balanced three phase load pulling 10A and the rest single phase loads, the neutral current would be 30A. If it was all one inbalanced three phase load then you're quite right, the neutral current would be 17.3A

 

[telectrix]

I said it was a sweary word man!
Thas aanly one wi C man!

....
nope . there's 2. ......creamflow.

 

[Chr!s]

Without information as to the nature of those loads, no answer can be gien. If they were all single phase resistive loads the neutral current would be 40A. If there was a balanced three phase load pulling 10A and the rest single phase loads, the neutral current would be 30A. If it was all one inbalanced three phase load then you're quite right, the neutral current would be 17.3A

As a basic question you have all you need, you have the loads on each phase and a neutral, it doesn't matter what's on the end of them.

Not sure how you arrived at 17.3, i get 15 amp


Chris

 

[Simonslimline]

As a basic question you have all you need, you have the loads on each phase and a neutral, it doesn't matter what's on the end of them.

Not sure how you arrived at 17.3, i get 15 amp


Chris

How did you get 15a?


N=√((A²+B²+C²)-((A×B)+(A×C)+(B×C)))



x = A cos 0 + B cos 120 + C cos 240
y = A sin 0 + B sin 120 + C sin 240
N = √(x²+y²)

 

[Chr!s]

How did you get 15a?


N=√((A²+B²+C²)-((A×B)+(A×C)+(B×C)))



x = A cos 0 + B cos 120 + C cos 240
y = A sin 0 + B sin 120 + C sin 240
N = √(x²+y²)

IN = I L1 + I L2 + l L3

cheers

 

[Simonslimline]

IN = I L1 + I L2 + l L3

cheers

You have lost me now sorry.