195.MET September 2022 Q.6(b)

Three impedances Z=5+j4 are connected in the form of a delta to the three loads of a balanced 3- phase circuit. The line voltage is 120 Volts. Find (a) The phase current, (b) Power factor, (c) The volt-ampere in the circuit

In a delta connected 3 phase system

Vline = Vphase

Iline = √3 Iphase

Iphase = Vline / Z

Inductive reactance X = 4 ohm

Resistane R = 5 ohm

Impedane Zph = 5+j4 = 6.40∠ 38.66^o

^{1) Iph = Vline / Z}

           ^{= 120 / 6.40}

           ^{= 18.75 A}

²⁾  φ = 38.66

     Power factor cos φ = 0.78

3)  So Vline = Vph = 120 V

           Iph = 18.75 A 

Volt ampere = Vph x Iph

                    = 120 x 18.75 = 2250 VA