Little help

[PeterPan27]

Had this question in a test. Was I right??

will try remember it all...

ring main 37 metres long wired in 2.5 mm twin earth.
Work out the ze (might not been ze) each r1 rN r2
2.5mm = 7.41
1.5mm = 12.10
the ze for this is 0.25 ohms


i basically did r1 is 7.41 x 37 divide by 1000 = 0.27 ohms
rN the same
r2 = 12.10 x 37 dived by 1000 = 0.44 ohms


so basically R1 +R2 = 19.51x 37 divide by 1000= 0.72 ohms

so zs would be 0.97 ohms ?????


hope. This makes sense or a little

 

[Octopus]

Try again.

 

[telectrix]

hint.... 4.
you have got confused. you have pulled the 19.51 from tables . it's not given in the question. you should be working solely from the r1 and r2 values given .

 

[PeterPan27]

I thought u did the divide by 4 at the end.
Not on the r1 rN r2?

would they mark my answer completely wrong?

 

[PeterPan27]

Ye mate the 7.41 and 12.10 was in question c

 

[telectrix]

edited due to beer calculating in error. R1+R2 = 0.71/4. 0.177 ohms.

 

[PeterPan27]

I just hope the exminer takes little pitty and gives me marks

 

[iamelectric]

taking ur inspection & testing course?

 

[PeterPan27]

This was 2394

 

[Spark_shark]

I got r1 and rn loops as 0.27(7.41*37/1000) and r2 as 0.45(12.10*37/1000).

r1+r2/4= R1+R2 expected @ at each socket.

0.45+0.27/4= 0.18 is R1+R2

Zs=Ze +(R1+R2)

Zs=0.25+(0.18)

Zs=0.43

 

[mtfpuk2011]

what was the paper like I passed my 94 from june and doimg 95 in mext few months the brake down of the question anser looks ok to how many marks was it

 

[PeterPan27]

Same as me tbh that mate

I got r1 and rn loops as 0.27(7.41*37/1000) and r2 as 0.45(12.10*37/1000).

r1+r2/4= R1+R2 expected @ at each socket.

0.45+0.27/4= 0.18 is R1+R2

Zs=Ze +(R1+R2)

Zs=0.25+(0.18)

Zs=0.43