Subject Name: Electro Mechanical Energy Conversion
Time: 02:30 PM TO 05:00 PM
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Instructions:
- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
Q.1 (a) What is electromagnetic induction? State and explain Faraday’s laws. (03)
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(b) Explain various effects of Air gap in Ferromagnetic Circuit. (04)
(c) Explain how magnetic field is established in a long solenoid when a dc current is passes through it using suitable diagrams and expressions. (07)
OR
Q.1 (a) What is hysteresis loss? Explain hysteresis loop with diagram. (03)
(b) State and explain different approximation made while analyzing electromagnetic devices. (04)
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(c) Draw and explain doubly excited magnetic field system. (07)
Q.2 (a) Explain DC series generator in detail with load characteristics. (03)
(b) Define field energy and coenergy. What is the significant of coenergy? (04)
(c) Draw and explain the characteristics of a DC shunt motor. (07)
OR
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Q.2 (a) A 746 kW, 3-phase, 50 Hz, 16-pole induction motor has a rotor impedance of (0.02 + j 0.15) Q standstill. Full load torque is obtained at 360 rpm. Calculate (i) the speed at which maximum torque occurs; (ii) the ratio of maximum to full load torque; (c) the external resistance per phase to be inserted in the rotor circuit to get maximum torque at starting. (03)
(b) Describe with neat sketches the construction of a 3-phase wound induction motor. (04)
(c) What are the advantages of rotating field alternator? (07)
Q.3 (a) A 120 V dc shunt motor having an armature circuit resistance of 0.2 Q and field circuit resistance of 60 Q, draws a line current of 40 A at full load. The brush voltage-drop is 3 V and rated full load speed is 1800 rpm. Calculate: (i) the'speed at half load; (ii) the speed at 125 per cent full load. (03)
(b) Compare cage and wound 3-phase induction motor with reference to construction, performance and applications. (04)
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(c) A short shunt compound dc generator delivers 100 A to a load at 250 V. The generator has shunt field, series field and armature resistance of 1300, 0.1Q and 0.1Q respectively. Calculate the voltage generated in armature winding. Assume 1 V drop per brush. (07)
OR
Q.3 (a) Describe the construction and working of a shaded pole induction motor. (03)
(b) Calculate the highest speed at which (i) 50 Hz (i1) 60 Hz alternator can be operated. (04)
(c) Write a short note on repulsion motor. (07)
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Q.4 (a) Using double revolving field theory, explain why a single phase induction motor is not self starting. (03)
(b) Briefly explain the principle of operation of dc servomotors. (04)
(c) Write a short note on hysteresis motor. (07)
OR
Q.4 (a) Describe the construction, working and uses of a reluctance motor. (03)
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(b) What are the advantages and disadvantages of PMDC motors compared with conventional dc motors? (04)
(c) Discuss the modifications necessary to operate a dc series motor satisfactorily on single phase ac supply. (07)
Q.5 (a) Name the most popular types of stepper motors. Describe the operation of a permanent magnet (PM) type of stepper motor. (03)
(b)
(c)
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OR
Q.5 (a)
(b)
(c)
Date: 20/06/2019
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Total Marks: 70
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER-V (NEW) EXAMINATION - SUMMER 2019
Subject Code: 2152001
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This download link is referred from the post: GTU BE 2019 Summer Question Papers || Gujarat Technological University
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