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simple one

simple one

simple one

(OP)
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
 

RE: simple one

Yes you can

RE: simple one

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).

RE: simple one

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

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