Browse  |   Placement Papers  |   Company  |   Code Snippets  |   Certifications  |   Visa Questions Post Question  |   Post Answer  |   My Panel  |   Search  |   Articles  |   Topics  |   ERRORS new
 Did you received any Funny E-Mails from your Friends and like to share with rest of our friends? Yeah!! you can post that stuff   HERE

 Categories >> Engineering >> Electrical Engineering

 Civil Engineering Interview Questions (2988) Mechanical Engineering Interview Questions (3263) Electrical Engineering Interview Questions (13162) Electronics Communications Interview Questions (2344) Chemical Engineering Interview Questions (407) Aeronautical Engineering Interview Questions (76) Bio Engineering Interview Questions (16) Metallurgy Interview Questions (79) Industrial Engineering Interview Questions (162) Instrumentation Interview Questions (2308) Automobile Engineering Interview Questions (104) Mechatronics Engineering Interview Questions (38) Marine Engineering Interview Questions (43) Power Plant Engineering Interview Questions (69) Engineering AllOther Interview Questions (1185)
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
Question Submitted By :: Ksawasthi
I also faced this Question!!     Rank Answer Posted By

Re: 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.
# 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 ? 344 Yes 181 No
Er. Ankush Miglani 0971815107

Re: 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.
# 2
You want the appropriate cable size then just apply the
frml P=V*I*Cos#
Where voltage = 0.240
Load is given and cos# lie between 0.8 to 0.9
you can easily get the ampere rating and choosecable size.

 Is This Answer Correct ? 110 Yes 197 No
Er.Nitesh
[APIL]

Re: 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.
# 3
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 ? 88 Yes 73 No
Mohammed Motawe

Re: 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.
# 4
good

3phase cable size calculation formula

 Is This Answer Correct ? 183 Yes 68 No
Tharik

Re: 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.
# 5
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 ? 43 Yes 33 No
Premgin

Re: 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.
# 6
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 ? 65 Yes 28 No
Robert Nithin

Re: 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.
# 7
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 ? 31 Yes 26 No
Nour Travis

Re: 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.
# 8
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

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 ? 50 Yes 25 No
Anupam Mathur

Re: 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.
# 9
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 ? 50 Yes 14 No
Bala

Re: 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.
# 10
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 ? 38 Yes 18 No
Bala