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Question
I want formula to calculate cable size as per load given in 
kw & amp.I searched many sites but didn't right answer.Plz 
reply me asap.
 Question Submitted By :: Electrical-Engineering
I also faced this Question!!     Answer Posted By  
 
Answer
# 1
sorry i dont have the xat formula for that but
for ALUMINIUM CABLE: 1sq.mm = 1.2 A of current
CU: 1sq.mm = 5.0 A of current
and the relation b/w A & KW IS
1KW= 1000*A*240*COS#
A- CURRENT
240= VOLTAGE
COS# = POWER FACTOR (.8 TO .99)
NOW IF U KNOW THE EXACT CURRENT LOAD OR LOAD IN THE FORM OF
KW U CAN EASILY FIND THE AMPERE RATING.
AFTER FINDING THE AMPERE RATING U CAN CALCULATE THE THE
SIZE OF THE CABLE. ANKUSH MIGLANI
9718151073
ankushmiglani2000@gmail.com
 
Is This Answer Correct ?    358 Yes 188 No
Er. Ankush Miglani 0971815107
 
Answer
# 2
good

3phase cable size calculation formula
 
Is This Answer Correct ?    205 Yes 77 No
Tharik
 
 
 
Answer
# 3
mv= (VD*1000)/L*I

VD= VOLTAGE DROP(AS PER COUNTRY STANDARDS)
L = LENGTH OF CABLE
I = CURRENT RATING
I = P/(1.73*V*PF)
PF= POWER FACTOR
MV= MILLI VOLTAGE DROP/AMP/METER

SELECT THE CABLE DEPENDING UPON THE MV RATING IN PRODUCT CATALOGS
 
Is This Answer Correct ?    70 Yes 28 No
Robert Nithin
 
Answer
# 4
Hai
First u will convert the KW OR kvA loads to AMph
After u can select the suitable cable from cable manufuture
catalouge . that u will consider derating factor = 0.72
For Example
50 A
16 SQ XLPE Al cable may be suitable
The 16 sqmm cable suitable for 70A ( DATA TAKEN FROM
HAVEELS CATALOUGE)
70 * 0.72 = 50.4 A
So the cable suitable for the above load.
after u will cross check voltage drop for the cable
 
Is This Answer Correct ?    54 Yes 15 No
Bala
 
Answer
# 5
Cable size depends on 1)Voltage Drop, 2)Distance, and 3)Load
So u have to calculate first the permissible voltage drop.
For lighting circuit permissible voltage drop:
2% of the rated voltage + 1 volt
2 X 230 /100 +1 = 460/100 + 1 volt = 5.6V

For motoring load
5% of the rated voltage

5 X 415/100 = 20.75 V

Now the formula for calculating voltage drop:

Voltage Drop = I X D (r X 0.85 + Xc X 0.53)/No. of runs X 1000
I : Current
D : Distance
r : Resistance
Xc : Capacitive reactance

If the voltage drop comes within the limits then ur cable
selection is ok.
 
Is This Answer Correct ?    53 Yes 27 No
Anupam Mathur
 
Answer
# 6
i will give you the basic eqaution,

PL = V*I*Pf=S*Pf ; i need to calculate the load current ,

I= PL/(V*Pf); as per ADDC(abu dhabi electricity), Pf=0.9
V=230 volt,

From the load CURRENT i can choose the rated current of
cable, take into account the voltage drop, so refer to
cataloge of any cables and wires company like oman cables

regarding with three phase just put cu(3) in the equations
best regards
 
Is This Answer Correct ?    97 Yes 77 No
Mohammed Motawe
 
Answer
# 7
Hai
The formula is delda v =
rt3 x I X Z X L/ 1000 x no OF runs
% OF VOLTAGE DROPS = Deta v
------ X 100
APPLIED VOLTAGE
The % of voltage voltage drops should be below 3 %
I = Requird current
Z = Cable impedance
L = cABLE LENGTH

First how many Amp you required
Example - 80
then you go to cable catalouge find out suitable cable
size
then calculate original current carring capacity of that
cable and multifly with 0.72 ( derating factor )
example in catalouge may be 35 sq mm cable and current
carring capacity may be 125 A
125 X 0.72 = 90
The carring carring capacity point of view this cable will
be ok
next you will check voltage drop with help of above said
fomula
 
Is This Answer Correct ?    41 Yes 21 No
Bala
 
Answer
# 8
See dear the basic soultion to cable size calculatiion in
sismple form can be done like this

Vd= ( mv* I * lenghth)*100/(400*1000)

I u can calualte from the Kw value for the particular pf
simple P/554

L required length

mV is the volatage drop/amp/km that can be obtained for the
particluar size of cable from supplier

eg. for 4cx16 its around 2.5 for most suppliers

100/400 is just amultiplication factor for converting it in
to 3 phase


Now do calulation and check if voltage drop limit is below
2.5 or 4 as per your standards


Simple.

But be cutious this is the simplest method and suitabel
method,many factors like grouping factor,derating
factor,spacing factor,type of laying,etc has to be taken
for apt analysis

Software like E Tap can also be utilised
 
Is This Answer Correct ?    45 Yes 36 No
Premgin
 
Answer
# 9
We can use fromula for Voltage Drop Calculation
VD = mVxIxL/1000
VD = Voltage Drop
mV = Milli Volt(Given Rating Cable Manufacture)
Example 16sqmm mV =2.5 mv/a/m
I = Load Current
L = Lenght of Cable
Exapmle #
Voltage = 415vAC, Ampere = 25, Length of Cable = 100Meter

VD = 2.5x25x100/1000
= 6250/1000
= 6.25 (in volt)
= 1.50% (in percent)
 
Is This Answer Correct ?    9 Yes 0 No
Tauqeer Hussain
 
Answer
# 10
Voltage drop works on Ohms Law.Multiply the route length in
metres by the the number of ampers of current that the
appliance draws,and then multiply by the number of milivolts
per ampere metre (mV/A.m)
Formula: Vd = L x I x Vc /1000
Where: Vd is the voltage drop measured in volts
L is the length of the cable in metre
I is the circuit current in Ampere
Vc is the millivolts per amper per metre droped
along the cable
1000 is a correction factor applied because Vc is in
millivolts and Vd is in volts.
 
Is This Answer Correct ?    36 Yes 28 No
Nour Travis
 

 
 
 
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