# calculating total amps and watts used by 3 phase system

#### cabo

Joined Jan 28, 2011
1
Need a little help with calculations: I've taken voltage, amperage, watt & PF measurements for each phase of a 440V 3 phase/ 4wire panel with an Extech power quality clamp meter. The measurements were made by measuring each line to neutral (not between the phases). Now that I have all the individual line readings, I want to calculate the total amount of watts and amperage being used on this panel by all 3 phases.
My measurements were:
L1: 260V, 60A, 12.20KW, PF-76
L3: 268V, 56A, 11.10KW, PF-74
L3: 263V, 52A, 10.80KW, PF-79

How can I calculate the total amount of amps & watts being used on this 3 phase panel?

Last edited:

#### Heavydoody

Joined Jul 31, 2009
140
Now that I have all the individual line readings, I want to calculate the total amount of watts and amperage being used on this panel by all 3 phases.
I assume by "used" you mean real power (as opposed to reactive). See if this helps:

$$Apparent Power (S)=|V_{rms}|\times|I_{rms}| Power Factor(pf)=\cos(\theta_v-\theta_i) Real Power(P)=S\cos(\theta_v-\theta_i) P_T=P_1+P_2+P_3 I=\frac{P}{V}$$

Also, note that your power factors are decimals (-.76) and the negative indicates a capacitive load. Hope this helps.