ASSIGNMENT 1 SCHOOL OF ELECTRICAL AND ELECTRONICS ENGINEERING COURSE TITLE: INDUCTION AND SYNCHRONOUS MACHINES COURSE CODE: ELE 300 MAX.MARKS:20 DATE OF ALLOTMENT: 31/08/2012 DATE OF SUBMISSION: 06/09/2012 . 1) What is meant by a Double cage Induction motor? 2) Explain the effect of rotor resistance and supply voltage on torque slip curve. 3) Define pull out torque locked rotor torque. 4) A 440 V 50 hz 6 pole 3 phase induction motor draws an input power of 81 KW from the mains. The rotor emf makes 120 complete cycles per minute. Its stator losses are 1 KW and rotor current per phase is 65 amperes. Calculate: (i) Rotor copper losses per phase (ii) Rotor resistance per phase (iii) Torque developed 5) A 400 V 6 pole 50 hz 3 phase induction motor develops 20 HP inclusive of mechanical losses when running at 965 rpm the power factor being 0.87 lagging. Calculate (i) slip (ii) rotor copper losses (iii) the total input if the stator losses are 1500 W (iv) line current (v) number of cycles made per minute by the rotor emf. 6) The rotor of an induction motor is skewed why? 7) The starting torque of a 3 phase induction motor can be increased by increasing the __ ____
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