Roll No. :... Total No. of Questions: 09] [Total No. of Pages: 02 B.Tech. (Sem. - 5th) ASYNCHRONOUS MACHINES SUBJECT CODE: EE -301 Paper ID : [A0413] (Note: Please fill subject code.and paper ID on OMR] T~me : 03 Hours Maximum Marks: 60 Instruction to Candidates: . 1) Section -A is Compulsory. 2) Attempt any Four questions from Section - B. 3) Attempt any Two questions from Section - C. Section - A Q1) (10 X 2 =20) a) What is meant by synchronous and asynchronous torques? b) Comment on the statement that "The rotating fields of the stator and rotor are stationary with respect to each other". c) Why windings ofAC machines are generally short pitched? d) Give merits and demerits of slip ring induction motor over squirrel cage induction motor. e) Why is the air gap between statOrcore and rotor made as small as possible? f) What will be the effect when stator voltage and freqU'encyof an induction motor are reduced proportionality? g) What is meant by crawling in a three..:phase induction motor? h) Mention few applications of Linear Induction Motor. i) State working principle of repulsion motor. j) Give liinitations and applications of stepper motor. J-378 [8129J P.T.o. Section - B (4 X 5 = 20) Q2) How the rotor does rotates in three phase induction motor? Justify. Q3) The efficiency-of a 400V, 3-phase, 6-pole induction motor drawing a line current of80 Amp, at 0.75I power factor at 4% slip is 85%. Calculate the shaft output and shaft torque. Q4) Draw and discuss the torque slip characteristics of 3-phaseinduction motor with increasing values of rotor resistance. Q5) Discuss schebius scheme of speed and power factor control of induction motor. Q6) Explain salient features of single phase series motor. Section - C (2 x 10 = 20) Q7) Discuss briefly the starting methods of 3-phase induction motor. The rotor of a 4-pole,.50 Hz, slip-ring induction motor has a resistance of 0.3 ohms per phase and runs at 1440 rpm at fullJO(id.Calculate the external resistance per phase which must be added to lower the speed to 1320rpm, the torque being the same as before. Q8) (a) Explain the operation of a capacitor start-capacitor run single phase induction motor. (b) Explain the construction of permanent magnet stepper motor. Draw the operating characteristics of stepper motor. Q9) Write short notes on the following: (a) Repulsion motor. (b) Linear Induction Motor. ~~~ J-378 2.