UNIVERSITY OF BOTSWANA
EEB241 Assignment I - Feb/ March
2019
AC Circuits
Department of Electrical Engineering
,
Faculty of Engineering and Technology
18 February - 1 March, 2019 Hand-in date: Friday 8 March 2019
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ELECTRICAL FUNDAMENTALS NOTES, Lecture notes of Electrical Engineering
STUDY NOTES ON TRANSFORMERS, SEMICONDUCTORS AND AC MACHINES
Typology: Lecture notes
2018/2019
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UNIVERSITY OF BOTSWANA
EEB241 Assignment I - Feb/ March
AC Circuits
Department of Electrical Engineering
Faculty of Engineering and Technology
18 February - 1 March, 2019 Hand-in date: Friday 8 March 2019
Assignment I : Single- and three-phase circuit analysis
- A load across a 230-V, 50-Hz single-phase AC voltage system consists of a motor with a nameplate rating of 25 KVA at a power factor 0.8 lagging; a capacitor rated 11KVAr; a 15-kW resistive load and a coil rated 18kW at 0.9 lagging. (i) Draw a sketch circuit and phasor diagram illustrating the above load connections ...............................................................................................................(06 marks) (ii) Calculate the total active, reactive and apparent power ........................(16 marks) (iii) Calculate the circuit phase angle and power factor ..............................(03 marks)
- (a) Using complete labelled phasor diagrams, distinguish between a: (i) Resistive-inductive and a resistive capacitive load impedance ............(04 marks) (ii) Resistive-inductive and a resistive-capacitive voltage ........................(04 marks) (iii) Resistive-inductive and a resistive-capacitive current .......................(04 marks) (iv Resistive-inductive and a resistive-capacitive single-phase power ......(04 marks) (v) Lagging and a leading current ...........................................................(02 marks) (vi) Lagging and a leading phase angle ...................................................(02 marks)
- (b) Using clearly labelled circuit diagrams, distinguish between the following methods of measuring single-phase power: (i) Single-wattmeter method .....................................................................(01 marks) (ii) Two-wattmeter method .......................................................................(02 marks) (iii) Three-wattmeter method ...................................................................(02 marks)
- Each branch of a three-phase star-connected load consists of a coil of resistance 4.2 and reactance 5.6 . The load is supplied at a line voltage of 415V, 50Hz. The total active power supplied to the load is measured by the two-wattmeter method. (i) Draw a circuit diagram of the wattmeter connections ........................(05 marks) (ii) Calculate their separate readings. ......................................................(20 marks)