simple one

[bigheadted]

if i have been qouted that a machine pulls 50A per phase can i apply 50A as IL in this this to the calculation to work out the power drawn

KW = VL x IL x 1.73 x PF
-----------------------
1000

thanks

 

[buzzp]

Yes you can

 

[snagit88]

Yes you can. IL = line current or treat it as the phase current. Where VL is your line voltage at a single point. The 1.73 is there as a square root of 3 (3 phase).

 

[aolalde]

That formula is correct for a balanced three phase circuit, were:

IL = Line current
VL = Line to line voltage
PF = Power factor
1.732= SQRT(3)

SQRT(3) factor is due to the vectorial relationship of the phase voltage Vph to the line to line voltage Vll ( imagine an equilateral triangle with 120° , 30°, 30° angles , the side opposite to 120° is the Vll and the other two equal sides are phase voltages Vph). Combine that with the total power produced by the three phases.

Vph = ½*Vll/cos(30°)

The power per phase is ; VAph = IL*1/2*Vll/cos(30°)

The total power in the system is tree times due to the number of phases (3 phases)

VAtotal = 3*[(1/2*Vll)/cos(30°)]*IL = 1.732*Vll*IL ; kVAtotal = VAtotal/1000

since PF = kW/kVA

kW = PF*kVA= 1.732*Vll*IL*PF/1000