calculate the minimum value of the cross-sectional-area
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using my question sheet that was the correct answer and you have explained it very clear thanks very much. i have 2 more question i having been trying to answer for 2 days now. if its not to much trouble thanks.
i have supplied the question and the answer but i don't understand how to get this answer could you please explain. this is the last 2 promise.
20 The fault current due to an earth fault of negligible impedance in a 400 V, three phase, four wire circuit
having an earth loop impedance of 0.3 ohms, is
a 1383A
b 767A
c 124.5 A
d 72A.
Answer b 411.4.5
37 A circuit is protected by a 10 A BS 3036 semi-enclosed (rewireable) fuse. The minimum permissible
current rating (Iz) of a conductor protected by this fuse would be
a 7.25A
b 10A
c 13.8A
d 20A.
Answer c appx5 5.1.1
i have supplied the question and the answer but i don't understand how to get this answer could you please explain. this is the last 2 promise.
20 The fault current due to an earth fault of negligible impedance in a 400 V, three phase, four wire circuit
having an earth loop impedance of 0.3 ohms, is
a 1383A
b 767A
c 124.5 A
d 72A.
Answer b 411.4.5
37 A circuit is protected by a 10 A BS 3036 semi-enclosed (rewireable) fuse. The minimum permissible
current rating (Iz) of a conductor protected by this fuse would be
a 7.25A
b 10A
c 13.8A
d 20A.
Answer c appx5 5.1.1
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20 The fault current due to an earth fault of negligible impedance in a 400 V, three phase, four wire circuit
having an earth loop impedance of 0.3 , is
a 1383A
b 767A
c 124.5 A
d 72A.
Answer b 411.4.5
An Earth Fault means 230V/0.3= 766.67
having an earth loop impedance of 0.3 , is
a 1383A
b 767A
c 124.5 A
d 72A.
Answer b 411.4.5
An Earth Fault means 230V/0.3= 766.67
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37 A circuit is protected by a 10 A BS 3036 semi-enclosed (rewireable) fuse. The minimum permissible
current rating (Iz) of a conductor protected by this fuse would be
a 7.25A
b 10A
c 13.8A
d 20A.
Answer c appx5 5.1.1
10A x 0.725 (Rating Factor for rewirable fuses) = 13.79A which rounds up to 13.8
HTH cheers
current rating (Iz) of a conductor protected by this fuse would be
a 7.25A
b 10A
c 13.8A
d 20A.
Answer c appx5 5.1.1
10A x 0.725 (Rating Factor for rewirable fuses) = 13.79A which rounds up to 13.8
HTH cheers
the doctor
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Hi
Post 7 is correct but post 8 is sort of :| ....
A 10A rewireable fuse can only protect a cable of maximum 13.8 A as
remember you can overload a wire for 1.45 so 1.45X 13.8 =20A(433 somewhere)
a rewireable has a "fusing factor" of 2 ( showing my age here!) and 2X10=20A (appendix 4)
Post 7 is correct but post 8 is sort of :| ....
A 10A rewireable fuse can only protect a cable of maximum 13.8 A as
remember you can overload a wire for 1.45 so 1.45X 13.8 =20A(433 somewhere)
a rewireable has a "fusing factor" of 2 ( showing my age here!) and 2X10=20A (appendix 4)
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