Answer to Question #162290 in Electric Circuits for Maxwell

Question

A balanced three phase load has per phase impendance of 25+j40 ohms if 400v three phase supply is connected to the load determine the

Phase current

Line current

Power factor

Power supplied to the load

Answer 1

Phase impedance: $Z_P = \large\frac{Phase \space Voltage}{Phase \space Current}$

We have $Z_p = 25+40j \space [omh]$ $U = 400V$

$I_p = \large\frac{U}{Z_p\sqrt{3}}$ $= \large\frac{400}{40\sqrt{3}}$ $= 5.78A$ (Phase Current)

$I_L = \sqrt{3}I_P = 10A$ (Line Current)

$cos \varphi= \large\frac{Rp}{Zp}$ $= \large\frac{25}{40}$ = 0.8125 (Power factor)

$P = \sqrt{3}U_LI_Lcos\varphi = \sqrt{3}*10*400*0.8125 = 2500\sqrt{3}$ W