Electric Circuits and Networks

8.10 COMPLEX POWER UNDER SINUSOIDAL STEADY-STATE CONDITION

Can we get the P and Q values from the voltage phasor and the current phasor straightaway by multiplying them together? We will try. Let V = V_rms∠φ_v V rms be the voltage phasor and I = I_rms∠φ_i A rms be the current phasor; both specified as rms quantities. Then,

 

 

We are not able to identify P or Q in the real and imaginary parts of this quantity since we know that P = V_rmsI_rms cos(φ_v – φ_i) and Q = V_rmsI_rms sin(φ_v – φ_i), but this observation prompts us to try VI^* instead of VI