IES COLLEGE OF TECHNOLOGY, BHOPALB.E. (EE Diploma 4th Semester) MID SEM-1Electrical Machine -II (401)Maximum Marks: 28 Minimum Pass Marks: 14Note:-Attempt all questions. Times: 2 Hours.Unit 1(a) What is the meant by slip in an induction motor. (June 20011) (b)Explain why a 3 phase induction motor, at no load, operates at a very low power factor.(Dec 2012) (c) Explain why the rotor of three phase induction motor can never attain synchronous speed.(Dec 2013)(d) Draw and explain torque slip characteristics of the three phase induction motor. (Dec 2013)

223

7

Unit 2 (a) Why starters are necessary for starting induction motor.[Dec 2011](b) Name different starting methods for 3-phase induction motor.(June 2011) (c) Explain about induction generator. [June 2012](d) Determine the approximately the starting torque of an induction motor in terms of full load torque when started by means of:(a) A Star delta switch(b) An autotransformer with 70.7% toppings. The short circuit current of the motor at normal voltage is 6 times the full load current and full load slip is 4 %. [June 2011] 223

7