Amps per phase calculation

[dldavies]

Could somebody please help me check my calculation for amps per phase for a 50KW total load over 3 phases and tell me what it should be.

Thanks in advance.

 

[wallyanker]

You haven't posted your calculation for us to check.......

 

[dldavies]

I calculated 69.44 amps per phase. Is that right?

 

[garrywatters]

[h=3]Have you included your PF correction?

AC three phase kilowatts to amps calculation formula[/h] The current I in amps is equal to 1000 times the power P in kilowatts, divided by square root of 3 times the power factor times the voltage V in volts:
I = 1000× P / (√3 × PF × V )
So amps are equal to 1000 times kilowatts divided by square root of 3 times power factor times volts.
amps = 1000×kilowatts / (√3 × PF × volts)
or
A = 1000 × kW / (√3 × PF × V)
[h=4]Example[/h] What is the current in amps when the power consumption is 0.33 kilowatts, the power factor is 0.8 and the voltage supply is 110 volts?
I = 1000 × 0.33kW / (√3 × 0.8 × 110V) = 2.165A

 

[dldavies]

You're quite correct, I hadn't included the PF figure. The new calculation I believe is 87 amps per phase.

Many thanks.

 

[wallyanker]

What supply voltage have you used to get that answer?

I get 90.2a, assuming its a 400v 3 phase supply

 

[dldavies]

I calculated it on 415v 3 phase supply.

 

[Knobhead]

At 415V at unity PF your first answer was right.

What PF did you use for your second answer?

 

[wallyanker]

415v at unity gives 69.56a per phase. As Tony said, how have you arrived at 87a per phase???

 

[Knobhead]

I worked out the PF for the 2nd answer must be 0.75 ? ? ? ?

 

[Afageeh]

I=KVA/(√3×KV)
I=(KW/PF)/(√3×KV)
I=(50/0.9)/(√3×0.4)= 80.19 A