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How to calculate cable sizes in with using motor KW? 
Any formula there?
 Question Submitted By :: Electrical-Engineering
I also faced this Question!!     Answer Posted By  
# 1
normally for copper cable 2.5amps 1sq mm
for alluminium cable 1.5 amps for 1sqmm
Is This Answer Correct ?    153 Yes 54 No
Khalander Mulla
# 2
normally for copper cable 2.5amps 1sq mm
for aluminium cable 1.5 amps for 1sq mm
That is the answer.......
Is This Answer Correct ?    33 Yes 11 No
Bethi Arun Reddy
# 3
3pahse power is P(in KiloWatt)=I.V.PF.(root 3).....
I=1.74 x P(KW)
so, assume 3ph 400V 15KW motor, In=1.74x15=26.1 A,
& 2xIn=Breaker rating= 52.2A
...choose 63A MCB

Cable size normally 20-25% higher than breaker to avoid
cable heat/burn accident in overcurrent fault. so, 1.25xIn=
62.64A so choose 80A Cable rating of 25mm2.
Is This Answer Correct ?    45 Yes 29 No
# 4
First of all you need to verified full load current of motor,
How can you calculate:
Ex: 1 Motor - 20HP 3ph. 415V 50Hz, 80% efficiency

Cal: A= HPx746/(sqrt3xVoltxPFxefficiency)



We all know that a motor has 1.5 times starting current,

Then 32.43x1.5 = 48.65Amp

Now you can see in the current currying capacity of cable from manufacturer cable's list.

3.5 x 35 sqmm xlpe cable is sufficient for full load.
Is This Answer Correct ?    35 Yes 23 No
Sagir Siddiqui
# 5
Hameent your statment is applicable for only small cable
size ( Up to 16 sq mm ) Please reff any one catalouge
Is This Answer Correct ?    29 Yes 18 No
# 6
We must consider numerous factors to calculate the exact
safe size of the cables for a particular load.
Please let us know whether the cable is to be laid in
ground or it will be overhead or any other way.
Secondly, you want an aluminium cable or copper cable?
Thirdly, the load is single phase or 3-phase?
Moreover, the motor is induction motor or any other type?
because we have to consider harmonics also.

For e.g for a 3-phase load of 80kw, the aluminium cable to
be laid inside the ground must be 150 for perfectly
safe operation.
Is This Answer Correct ?    7 Yes 4 No
# 7
First of all we will chk rated amp mentioned on motor then will check from chart abt cable sq mom size 
Is This Answer Correct ?    4 Yes 2 No
Rana Farrukh Anwsr
# 8
For Cable Current Capacity = 4X Size of Cable in, Ex. For 2.5 = 42.5 = 9 Amp. 
Is This Answer Correct ?    1 Yes 6 No
# 9
ex 10kw 3 phase ac motor,
10kw x 1.74 = 17.4 amp
MCB using 25 amp/30 amp 3 pole(C)
Motor using star-delta/overload setting 0.58 = 10.1 amp
cable size = 6x2.5mm2/1c pvc copper cable

if using soft starter
MCB using 25amp/30amp 3 pole MCB(C)
cable size = 3x4mm2/1c pvc copper cable

cable size :calculate include starter overload setting
(right or wrong,thank's)L
Is This Answer Correct ?    0 Yes 7 No
# 10
what's wrong with you guys. You dont even know how to spell
correctly. Please improve on that. Its not only about idea
but also on how you convey it. Damn!
Is This Answer Correct ?    3 Yes 11 No

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