# Just a quick question about Real 3 phase power

Discussion in 'Homework Help' started by Amanda_Riley, Apr 1, 2011.

1. ### Amanda_Riley Thread Starter New Member

May 12, 2010
22
0
The equations to find real power is:

P = 3 x Vphase x Iphase x cos(v - i)

or √3 x Vline x Iline x cos(v - i)

My question is if you have a delta connected 3 phase system and have

Vphase = Vline = 120 angle 0
Iphase = 41.6 angle -36.87
Iline = 72.05 angle -66.87

Would you use the angle of 36.87 for both the real power equations?

2. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
783
How did you arrive at ...

Vphase = Vline = 120 angle 0 ?

The phase(line)-to-neutral and phase(line)-to-phase(line) voltages can't be the same.

3. ### Amanda_Riley Thread Starter New Member

May 12, 2010
22
0
its delta connected - delta source and a delta load so no line to neutral line

Phase voltage (Vab) = Line voltage(VAB)
Line current = √3 x phase current

4. ### subtech Senior Member

Nov 21, 2006
123
5
In short, the answer is yes.

The phase measurement (some call this the winding current) is the current magnitude and angle to use in your calculation.