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Q7. An unbalanced, three-phase, star connected load is supplied from a four-wire, 440 V, 50 Hz supply. The current in EACH phase is:

• I_R= 7 A lagging VR by 30°

• I_s = 5 A in phase with Vs

• I_g = 9 A leading VT by 60°

(a) Sketch, approximately to scale, a labelled phasor diagram showing phase voltages and currents. (3)

(b) Calculate EACH of the following:

(i) the neutral current; (5)

(ii) the phase angle of the neutral current with respect to the S phase voltage; (2)

(iii) the total power dissipated. (6)