How you calculating the current for a 2.5 Sqmm cable.
A 30 Hp 3 phase AC motor of power what size of cable is
used for this motor.
Answers were Sorted based on User's Feedback
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
Is This Answer Correct ? | 24 Yes | 6 No |
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%.
Is This Answer Correct ? | 15 Yes | 9 No |
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
Is This Answer Correct ? | 6 Yes | 3 No |
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
Is This Answer Correct ? | 0 Yes | 0 No |
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.
Is This Answer Correct ? | 17 Yes | 23 No |
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