How to calculate the true power|!

[simo1991]

I need to calculate the true power and reactive power and i no the formula for true power is V x I x cos and reactive power is apparent power-true power squared. however the figures it have been given are the load size of 50KVA at a power factor of 0.7??? any help on this would be appreciated! thanks

 

[Guest123]

You have your load (apparent power) of 50KVA

True power (KW) = apparent power x PF = 50KVA x 0.7 = 35KW

Calculating reactive power (KVAr) is a bit more complicated, is this a single or 3 phase load???

 

[clicon357]

Simo, guessing you're at college maybe? PM me your email and I'll send you some stuff that may help with your calcs etc. Cheers.

 

[simo1991]

single phase

 

[Guest123]

To calculate KVAr, there are a couple of ways to do it - using the sine of the angle between KVA & KW for instance, or using inductive & capacitive currents & reactance.

Given the info you have, I would do it this way -

KVAr = KVA x sqrt 1-(pf x pf).

In your case KVAr = 50 x sqrt (1-(0.7 x 0.7)) = 50 x 0.714 = 35.7 KVAr.