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PSNA College of Engineering and Technology Department of Electrical and Electronics Engineering Modeling and Analysis of Electrical Machines Serial Test –II Class: ME (Power Electronics and Drives) Total Marks: 50 Sub: Modeling and analysis of Electrical Machines Sub Code: PE1601 Staff: M.Kaliamoorthy Date:28.10.09 PART A ANSWER ANY NINE QUESTIONS 9 X 2 = 18 1. The stator current of a three phase rotating electric machine with symmetrical stator 2 2 winding are I as 2 I a cos et , I bs 2 I b cos et , I cs 2 I c cos et 3 3 where the currents Ia,Ib and Ic are unbalanced. Comment on the total air gap mmf due to stator currents. 2. State whether for a three phase salient pole synchronous machine the mutual inductances between the stator windings are a function of rotor position under dynamic conditions. Explain your answer. 3. List various parameters of a synchronous machine 4. Give an expression for fundamental space MMF 5. Differentiate Concentrated and distributed winding. Explain why distributed winding is preferred. 6. Differentiate Short pitched winding and full pitched winding. Explain which is having more advantages. 7. Mention significance of rotating magnetic field. 8. Give the expression for transfer functions of DC motor. 9. Give the expression for MMF of field winding of synchronous motors 10. Give the expression for torque of induction machine. PART B Answer ALL questions 2 x 16 =32 11. (a) Draw the Magneto Motive Force Space wave and derive the expression of MMF for the following (i) Concentrated, Full pitched winding (ii) Distributed Winding (iii) Short Pitched winding. (16) (OR) (b) (i) Explain the steps involved in the computation of dc motor response and other quantities of interest with the help of a flow chart. (6) (ii) Discuss the various operational impedances for a synchronous machine with four rotor windings (10) 12. (a) From first principles derive the voltage and torque equations of a three phase symmetrical induction machine. (16) (OR) (b) For a 2 pole 3 phase wye connected salient pole machine derive the expressions for per phase winding inductances. (16) Staff Incharge HOD