Power Engineering Exam 2011-2012: ELEC7014, BEng in Electrical Engineering, Exams of Power Plant Engineering

Download Power Engineering Exam 2011-2012: ELEC7014, BEng in Electrical Engineering and more Exams Power Plant Engineering in PDF only on Docsity! Page 1 of 4 CORK INSTITUTE OF TECHNOLOGY INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ Semester 2 Examinations 2011 / 2012 Module Title: Power Engineering Module Code: ELEC7014 School: Electrical & Electronic Engineering Programme Title: Bachelor of Engineering in Electrical Engineering Programme Code: EELEC_7_Y3 External Examiner(s): Ms Mary Desmond, Mr Colm Murray Internal Examiner(s): Mr Joe Buckley Instructions: Answer 3 Questions ONLY. All questions carry equal marks. In marking scripts, the examiner will take account of clarity of expression and communication skills. Duration: 2 Hours Sitting: Summer 2012 Requirements for this examination: Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination. If in doubt please contact an Invigilator. Page 2 of 4 Q1. Part 1 “When a complex current wave exists in a circuit, each of the components harmonics can be looked upon as acting independently”. (i) Discuss this in the context of the following circuits: (a) An inductive circuit in which the resistance can be regarded as negligible. (b) A capacitive circuit in which the resistance can be regarded as negligible. (5 marks) (ii) Derive an expression for the current value of the third, fifth and seventh harmonic for (a) and (b) above. The expression to express the current in terms of the fundamental reactance x1 and the respective harmonic emf Eȝ, Eƽ and E7. (5 marks) Part 2 An e.m.f. is represented by e=100 sin ϴ + 30 sin (3ϴ+ 20˚) +10 sin (5ϴ + 10˚). The fundamental frequency is 50 Hz. i. Determine the r.m.s value of the current in a circuit in which R=5Ω, L = 0.02H. (5 marks) ii. Derive the equation for the current wave. (5 marks)