Answer / satish m

For three phase motor we needs to consider the PF also.
P = Sq.Rt 3 X V x I x pf

Answer / shannu

Unit consumption is KW x Hrs.

But while you need to calculate the KWH consumed by a motor,
multiplying KW of motor (nameplate KW) and hour will not
give you the energy consumed. This is because the name plate
KW in a motor is not the electrical power, but the
mechanical power output provided by the motor (Electrical
Power = Frictional losses + Eddy current losses + Copper
losses + air gap losses + Mechanical power). In order to
calculate the energy consumed by the motor you can use the
formula

single phase AC = Voltage x Rated current x Power factor x
Hrs run. (100% load)

3 Phase AC = 1.732 x Voltage x Rated Current x Power factor
x Hrs run. (100% load)

Normally the power factor of motor is considered between 0.8
to 0.85 at full load operation.

At no-load, motor will take approx 40% of its rated full
load current (again this depends on the design of motor, but
normally assumed to be near 40%). So at 50% load, the motor
will take a current around 70 to 75% of its full load rated
current. so we can approximate as

energy consumed at 50% load (motor - 3 phaase) = 1.732 x
Voltage x 75% rated full load current x power factor x Hrs run .

at no load = 1.732 x Voltage x 40% of rated current x power
factor x Hrs run.

Answer / shivpal prajapati

kwh=kw*hrs is not correct.
kw=1.732*v.i.0.85,if motor rated current 64amp,
Then calculated value kw=1.732*415*64*0.85

Answer / sakil belim

i have 70 hp 3 phase load. I run 70 hp in 1 hour in perday
what is kwh

Answer / tushar amarghade

for 100% load
unit(kwh)- kw*hours/1000
where,
KW for single phase- V*I*PF
KW for THREE phase- 1.732*V*I*PF

Answer / prabhu

In single phase
KW= Voltage X current
In 3 phase
KW= Sq.Rt 3 X V x I
For 100% load I=I
For 50 % load I= 50/100 X I= I/2

I is the rated current of the machine

sir,i am swati. i am goin to gv jspl exam on 21st nov'10. iwant previous year question paper. plz help me out. my emailid is swatisinha.dav@gmail.com

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