EXAMINATION PAPER

EXAMINATION PAPER ID NUMBER_______________ SEMESTER: YEAR 2 FACULTY/SCHOOL: SEAT NO:_________ 2009 CAMPUS SCHOOL Health, Engineering and Science SUBJECT CODES Engineering and Science SUBJECT TITLES VEF2004 (PLEASE LIST ALL CODES AND TITLES C F M S W B PLEASE MARK THE CAMPUS/S WHERE EXAM WILL BE SAT Systems and Applications 2D FOR WHICH THIS PAPER IS TO BE USED) DURATION OF EXAMINATION 3 THIS EXAMINATION COUNTS FOR HOURS + 15 MINUTES READING TIME 60 % OF THE ASSESSMENT IN THIS SUBJECT. EXAMINATION PAPERS DETAILS TOTAL NUMBER OF PAGES (including this one) 5 NUMBER OF QUESTIONS 8 NUMBER OF QUESTIONS TO BE ATTEMPTED All SPECIAL INSTRUCTIONS TO CANDIDATES Use a separate answer booklet for each section. EXAMINATION MATERIAL PERMITTED TO BE USED BY CANDIDATES : Section A: Analogue Electronics, Text Book “Microelectronic Circuits”, Sedra & Smith. Section B: Digital Electronics, Two A4 pages (sides) of written material. Section C: Energy Conversion, Two A4 pages (sides) of written material. EXAMINATION MATERIAL SUPPLIED BY STUDENT ADMINISTRATION YES NO  COMPUTER MULTIPLE CHOICE ANSWER SHEET YES NO  CAN THE EXAM PAPER BE RELEASED TO STUDENTS YES  NO  CAN THE EXAM PAPER BE RELEASED TO LIBRARY YES  NO  ANSWER BOOK YES 3 NO GRAPH PAPER EXAMINER/S A.Zayegh/Y.Ng/JShi EXT MODERATOR/S C.Ozansoy/J.Chlond/ W.S.Lee EXT 4858/4724 /4034 5046/4701/ 4053 CAMPUS Footscray CAMPUS Footscray (Examiner/s must be available on this number for duration of this examination)  VEF2004 Systems and Applications 2D (Section A, B & C) November 2009 Page 1 IMPORTANT INSTRUCTIONS TO STUDENTS SECTION A IS THE ANALOGUE ELECTRONCS SECTION SECTION B IS THE DIGITAL ELECTRONICS SECTION SECTION C IS THE ENERGY CONVERSION SECTION Please use a separate answer booklet for each section.  SECTION A: Analogue Electronics Question A1. (Frequency Response) (20 Marks) An MOSFET common-source amplifier has Rin = 2 MΩ, gm = 4 mA/V, ro = 100 kΩ, RD = 10 kΩ, Cgs = 2 pF. And Cgd = 0.5 pF. The amplifier is fed from a voltage source with internal resistance of 500 kΩ and is connected to a 10-kΩ load. a) Draw the circuit and label all components b) Find the overall mid-band gain AM c) Find the upper 3-dB frequency fH. d) If we want to double fH what is the most appropriate components to be change. Question A2 (Differential Amplifier) (20 Marks) Figure-1 is a BJT differential amplifier using transistors with  = 100 and VA = 100 V. a) Find the differential gain and the differential input resistance b) Find the common-mode gain Figure-1 Question A3 (Amplifier stability) (20 Marks) An op amp designed to have a low-frequency gain of 105 and high-frequency response dominated by a single pole at ω = 100 rad/s, acquires, through a manufacturing error, a pair of additional poles at ω = 10,000 rad/s. a) At what frequency does the total phase shift reach 180o? b) At this frequency, for what value of β, assumed to be frequency independent?  SECTION B: Digital Electronics Please see the separate pdf file for the Digital part of the exam.  SECTION C: Energy Conversion Question 1 (10 marks) Consider the magnetic structure shown in Figure 1. Find the current in the 50-turn winding to set up a flux density of 0.8T in the structure, assuming that the relative permeability of the core material is 2000. Use the concept of reluctance in your solution. Figure 1: Magnetic structure for Question 1. Question 2 (20+10=30 marks) A 15kVA 2300V/230V transformer is to be tested to determine its excitation branch components, its series impedances, and its voltage regulation. The following data have been taken from the primary side of the transformer: OPEN-CIRCUIT TEST Voc=2300 V Ioc=0.21A Poc=50W SHORT-CIRCUIT TEST Vsc=47V Isc=6.0A Psc=160W a) Find the equivalent circuit of this transformer referred to the high voltage side (primary) and draw the equivalent circuit diagram; (20 marks) b) Determine the efficiency of the transformer at full load with a lagging power factor of 0.8. (10 marks) Question 3 (20 marks). a) How many methods can be used for speed control of a DC motor? (5 marks) b) The armature resistance of a 220 V shunt motor is 2. At no load, the line current is 2.4 A at rated voltage. The field current is 0.8 A, and the speed is 1440 rpm. Find the motor speed when the line current increases to 12.8 A, the field current remaining the same. Assume that armature reaction does not affect the field flux. (10 marks) c) The counter emf of a shunt motor is 227V, the field resistance is 160, and the field current is 1.5A. The line current is 36.5 A. Find the armature resistance. If the line current during starting must be limited to 60A, how much starter resistance must be added in series with the armature? (5 marks)