SKEE2423 PERDANA FINAL EXAMS 201820191.pdf - 2 SKEE 2423 Q.1(a State two(2 advantages of three-phase system compared to a single-phase system(b(3 marks

# SKEE2423 PERDANA FINAL EXAMS 201820191.pdf - 2 SKEE 2423...

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2 SKEE 2423 Q.1 (a) State two (2) advantages of three-phase system compared to a single-phase system. (3 marks) (b) An unbalanced three-phase, delta connected load is connected to a three-phase star connected supply of 240 V rms per phase. The phase sequence is positive. The loads is given as below: Z AB = 30∠-41.40° Ω (between line A and B) ࠵? ࠵?࠵? = 70∠0° Ω (between line B and C) ࠵? 34 = 60∠25.84° Ω (between line C and A) Taking V AB on the load side as a reference, (i) (ii) determine all line currents. (7 marks) Determine total apparent power (S), active power (P) and reactive power (Q). (6 marks) (iii) Two wattmeters are used to measure the total active power received by the loads. Draw the connection of the two wattmeters if their current coils are in line A and C respectively. What are the total power measured by each wattmeter, W 1 and W 2 ? Compare your answer with Q.1(b)(ii). (9 marks)
3 SKEE 2423 Q.2 (a) (b) With the aid of formula/diagram, state Faraday’s Law. (3 marks) An iron ring made from cast steel has a cross sectional area of 3 cm 2 . An air gap of 0.2 mm has been made by a cut across its section. The effective iron path

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• Fall '20
• Electric power transmission, Electric power, Power factor, SKEE 2423

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