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AEIS Chap 3 Mst Revision (Answers)

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AEIS Chap 3 Mst Revision (Answers)
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  2008/2009 SEMESTER ONE EXAMINATION Section A 5. What is the typical aircraft single phase A.C supply? (a) 28V, 400Hz. (b) 115V, 400Hz.* (c) 230V, 50Hz. (d) 28V, 50Hz 6. Which of the following units are found in an integrated drive generator (IDG)? (a) The generator and the voltage regulator. (b) The generator and the constant-speed drive.* (c) The GCU (Generator Control Unit) and the constant-speed drive. (d) The GCU (Generator Control unit) and the alternator. 7. When the A.C generator speed increases, which one of the following statements are TRUE ? (i) The output voltage of the generator will increase. (ii) The output voltage of the generator will remain the same. (iii) The frequency of the output signal will increase. (iv) The frequency of the output signal will remain the same. (a) i & iii only* (b) ii & iii only (c) i & iv only (d) ii & iv only   Section B B3 (a) State 3 advantages of a brushless A.C. generator ( 3 marks) (i) Lower maintenance cost since there is no brush or slip-ring wear. (ii) High stability and consistency of output because variations of resistance and conductivity at the brushes and slip rings are eliminated. (iii) Better performance high altitudes because arcing at the brushes is eliminated. B3 (b) Figure B1 shows a half – wave rectifier circuit. Draw the output waveform develop across R L  given that the waveform at T 1  is shown in Figure B2. Assume that D1 is an ideal diode. ( 3 marks) Figure B1 Figure B2     2008/2009 SEMESTER TWO EXAMINATION Section A 7. Which one of the following statement is correct about a star- connected 3 phase distribution system? a. The line voltage leads the phase voltage by 30°.* b. The line current leads the phase current by 30°. c. The line voltage lags the phase voltage by 30°. d. The line current lags the phase current by 30°. 8. The function of an Integrated Drive Generator (IDG) in an aircraft electrical system is: a. To provide a constant input speed to the attaching generator in order to provide a constant frequency and voltage regardless of the engine speed and electrical load. b. To provides a constant frequency and voltage to the aircraft electrical system regardless of the engine speed and electrical load. * c. To drive the aircraft engine at a constant speed. d.   To provide a direct current to the aircraft electrical system only.   Section B B3 (a) Figure B2 shows the arrangement of the field windings of the 3 phase AC motor and figure B3 shows the AC waveforms going into the AC motor. Draw the magnetic field direction at 120° of the AC waveform as shown in Figure B3. Clearly label the arrangement of field windings of the 3 phase AC motor on your answer. Figure B2
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