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

 

[Megavolt]

Why not get your books out have a read through and come back and tell us the correct answer.

 

[Simonslimline]

I think its 20 as this is 5% of 400 but am really not sure.

I know for single phase it is 3% lighting and 5% for other circuits. I have searched for threads on here and cant seem to find an answer. It is something i also dont recall going over at college.

 

[HARRYSPADGE]

I say its 32v ?

 

[telectrix]

5% 0f 400 is 20. that's my answer. never seen 3 phase lighting.

 

[Simonslimline]

5% 0f 400 is 20. that's my answer. never seen 3 phase lighting.

This is what i thought. over 100 people have answered 8volts on the question. How many of them are sparks though i am not sure.

 

[HARRYSPADGE]

5% 0f 400 is 20. that's my answer. never seen 3 phase lighting.

I know nothing about 3 phase, I was just stabbing in the dark !

 

[Zebra Stripe]

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

strange question imo
lighting 3%
distribution 5%
Line to neutral 230v
Line to line 400v
therefore maximum volt drop would be 5% of 400v = 400x0.05 = 20v

 

[davesparks]

5% 0f 400 is 20. that's my answer. never seen 3 phase lighting.

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

 

[Simonslimline]

Was the maximum 4% in the 16th edition? so 16volts. Now 5% in the 17th at 20volts?

 

[Zebra Stripe]

Think the question is a city and guilds favorate, which gets repeated over and over again. So yep you'll find the answer as 16volts (4%) if you google it..

 

[shanky887614]

Think the question is a city and guilds favorate, which gets repeated over and over again. So yep you'll find the answer as 16volts (4%) if you google it..

not always.

if you do a little night time reading there are 4 values.

one for dno transformer and one for private

 

[Simonslimline]

Think this helps


IEE Wiring Regulations: Explained and Illustrated - Brian Scaddan - Google Books

 

[trev]

5% 0f 400 is 20. that's my answer. never seen 3 phase lighting.

I have, in a pub in Hexham. Mind you it wasn't supposed to be 3ph.

 

[Zebra Stripe]

Simon its a simple calc, the question is silly and doesnt relate to anything in reality, ie type of circuit, length of run, design curent,,,,,,,it just asks for maximum volt drop which could be 5% of 230v or 5% of 400v..its the usuall meaningless City&Guilds confuse the f out of everybody type of question.

 

[shanky887614]

Simon its a simple calc, the question is silly and doesnt relate to anything in reality, ie type of circuit, length of run, design curent,,,,,,,it just asks for maximum volt drop which could be 5% of 230v or 5% of 400v..its the usuall meaningless City&Guilds confuse the f out of everybody type of question.

could be 5 or 8% allowable depending on what the supply is from.

page 314 table 4ab

 

[Zebra Stripe]

Yep, didnt think of that could be a private supply:shocked3:

 

[Zebra Stripe]

so the answer is 32v

 

[Simonslimline]

Simon its a simple calc, the question is silly and doesnt relate to anything in reality, ie type of circuit, length of run, design curent,,,,,,,it just asks for maximum volt drop which could be 5% of 230v or 5% of 400v..its the usuall meaningless City&Guilds confuse the f out of everybody type of question.

I thought 20v was correct. Over 100 people have answered 8V so i was just wondering if i was missing something silly that was all.

I am happy it is 20v at 5% of 400 now.

 

[shanky887614]

its wrong really but people tale the onsite guide as gospel but in truth its a rule of thumb guide