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B2. (a) Unbalanced 4-wire Star-connected loads are connected to a 3-phase power supply of positive phase sequence (ABC) as shown in Figure B2(a). Phase voltage VAN = 100V20. The phase loads have impedances as listed below. ZA = 15 Q; ZB = 10 + j5 0; Zc=6+j8 Q. Calculate: (i) the line currents (Ia, Ib, IL) in polar form; (ii) the neutral current (In) in polar form; (iii) the line voltage VAB in polar form; (iv) the total active power dissipated by the loads. la (3 marks) (2 marks) (2 marks) (1 mark) A ZA N In ZB Zc B Ib Ie Figure B2(a) (b) A 380V, 50HZ, three-phase supply with positive sequence (RYB) has delta- connected loads as shown in Figure B2(b). Line voltage VRY = 380VZ15. The phase loads have impedances as listed below. ZRY = 20 + j4 2; ZYB = 10 - j8 2; ZBR = 4 + j12 Q. Calculate: (i) the phase currents IRy, Iyg and IBR in polar form; (ii) the line currents IR , Iy and Is in polar form. IR (6 marks) (6 marks) ZRY IRY ZBR I BR www. ZyB ly