Exam Question

(a) Derive the expression for current and voltage relations between line and phase values in the star and delta cases. Draw vector diagram. (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 (10)

(i) The phase current

(ii) Power factor

(iii) The volt-ampere in the circuit.