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Fall 2002 Final Exam


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MCGILL UNIVERSITY FACULTY OF ENGINEERING DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING FINAL EXAM POWER ENGINEERING, ECSE-361A DECEMBER 6, 2002: TIME 9:00 ANSWER ALL SIX QUESTIONS OPEN BOOK AND NOTES EXAM MAXIMUM POINTS = 75 Examiner: Prof. F.D. Galiana Associate Examiner: Prof. B.T. Ooi Problem 1 (10) Show how a salient pole synchronous motor can produce non-zero average torque even if the rotor current is zero. Use a simple machine model to demonstrate this. Problem 2 (15) A three-phase, 1kV, 20 kVA, wound rotor, induction motor operates at a no-load speed of 1490 rpm. The device operates at nominal voltage and consumes 0.9 pu real power at a lagging power factor of 0.8. The frequency of the rotor currents is 3 Hz. (a) Estimate the frequency of the stator currents and the number of poles. (b) Find the speed of rotation in rpm. (c) Find the torque in Nm produced by the motor. Problem 3 (10) The net magnetic field distribution in the air gap of a round rotor induction machine has a peak of 1 T and 7 pole pairs.
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