How we can design a cable for a 3phase load.
Answers were Sorted based on User's Feedback
Theory
From Ohms law, the voltage drop in an electrical conductor
is
V = I R
where
I = Current, amps
R = Resistance, Ohms
The electrical resistance can be derived from the
properties of the conductor material.
R = ρ L / A
where
ρ = Resistivity, Ω mm2 /m
L = Length, m
A = Cross sectional area, mm2
Watch the units in the above equation.
The resistance can also be expressed in terms of the
material conductivity (ψ) which is just the reciprocal of
the resistivity.
R = L / (ψ A)
Table 1. Typical material electrical conductivity
Material Conductivity, ψ
Copper 58
Aluminium 36
Mild Steel 7.7
Combining Ohms law with the resistance expression, we get.
V = (I L) / (ψ A)
Now, we can define an acceptable voltage drop in a
conductor. I have calculated the voltage drop that was
used in several published tables and get around 5.5 Volts.
We could therefore re-arrange this equation to give the
cable size. But cables come in standard sizes measured in
mm2. In addition, you also need to consider the maximum
current for each cable size.
Table 2. Conductor sizes and maximum currents
Cable Size, mm2 1.5 2.5 4 6 10 16 25 35 50 70 95 120 150
185 240 300
Maximum current, A 13 21 28 36 46 61 81 99 125 160 195 220
250 285 340 395
Is This Answer Correct ? | 3 Yes | 0 No |
Answer / vinothbabu.k
genraly cable slection was based on Rated load amps,voltage
drop,& fault current.
cable which can carry the 1.5 times of the rated amps,cable
shall be consider..
Is This Answer Correct ? | 2 Yes | 1 No |
Will sag depends on the Specific Resistance of the conductor?if not Why??????????
how many synchronous motor are there in any power plant
why need of ac exietation in alternater.
WHAT IS START TO INDUCTION MOTER IN STAR TO DELTA OF >5HP ?
HELLO SIR, IAM PREPARING HPCL EXAMS. SO PLS SEND MATERIAL OF HPCL ELECTRICAL ENG..TO VIJAY_8888@YMAIL.COM
What is q factor?
the site measured knee point voltage of protection class CTs should be greater than rated knee point voltage? what about meetering class CTs. Should it be below the rated knee point voltage?
which is dangerous AC or DC?
What should be value of Circuit breaker operating time and tripping time?
if a 3phase 100kva distribution transformer , 400 v,50 hz, 4-wire system is loaded at 160 k.w mostly 1-phase Lighting & Airconditioning split a.c load what will be the net effect on the power system in terms of voltage, powerfactor, current , efficiency of xformer
define the non synchoronism of synchoronous machine in general g or m??
Transformer cores are laminated in order to A simplify its construction B minimize eddy current loss C reduce cost D reduce hysterisis loss