Answer / shoyabkhan

the answer is wrong we can calculate by usbing this formula
W = 1.732*V * I Cos (phi)
30*746 = 415 * I * 0.8*1.732
I=36.2 AMP

Answer / shashank

deciding a cable has to consider following parameters also,
1. Safety factor of the cable (margin for starting current
say 1.25 in numerator side)
2. Deterioration / Degradation factor (say 0.8 in
denominator)
calculate the current of the motor by considering running
pf (power factor) say 0.8
as motor gives real power
e.g.
W = V * I Cos (phi)
30*746 = 415 * I * 0.8
I = 30 * 746 / (415*0.8)
I = 67.41 Amp,
Thus Current considered for cable (Icb) = 67.41*1.25/0.8
Icb = 105.3 Amps.
Select from the catalogue suitable copper cable for this
motor. Dont forget to consider the voltage drop per meter,
the total voltage drop shall not be more that + - 5%.

Answer / balakrishnan.t

For calculating the current rating of a 30 Hp 3 phase motor can be written as
power = sq root(3)* VL*IL*cos (phi)--------(1)
where 'VL' is line voltage, 'IL' - line current and cos phi- power factor

OR 3 EP*IP*cos(phi)
as the voltage fed is from three phase system.
Power input of 30 Hp motor = 30*746/(efiiciency*cos phi) watts
from the formula (1) and taking efficiency as 0.9,
Line current 'IL' = 30*746/(1.732*415*0.9*0.83)
= 41.68 Amps

Answer / shamsher singh

10sqmm cooper

Answer / ramesh insan

As per thumb rule
Power Sq root 3=1.732
Voltage =415
PF=0.8
Cos=0.85

1.732*415*0.8*0.85=488.77

30HP*746W=22380/488.77=45.79 Amp

Answer / amarnath

If its a 2.5Sq.mm Aluminium cable then it can take load
current upto 3Amps and if its Copper cable then it can take
a load current upto 9.4Amps.

And for a 30HP motor the cable size shall be 3.5Core X
16sq.mm Aluminium or 3.5Core X 6sq.mm Copper cable.

Answer / mrudang

we are measure through SWG ( standard wire guage
it measure the crossection of wire
2.5sqmm

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