If we feed three phase power to a star connected load having same impedance on all three arms then we can use formula: POWER=VxIxP.fx1.732, is it possible to use same formula if impedance is unequal in arms? If not how to calculate the power?
1) No, the formula stated cannot be used for an unbalanced load!
2) Simplifications are available that can be used to calculate power for either supply/load arrangement (delta or star) as well as the absence/presence of a neutral-wire for the star case!
The simple method is to make measure your per phase power and simply add them. I use a Fluke 43b for this but it is much simpler to connect a three phase power quality meter such as a Fluke 434. I have used this model for locating the sources of noise and distortion also. On the application page of the Fluke website they indicate that.
Making watt measurements with the Fluke 430 Series Power Quality meter
On the three phase 430 power
quality analyzers, the energy
function automatically measures
and calculates Watts/VA/VARs.
Simply connect the clamps and
leads and select energy from the
menu.
