Subject Code: 133402
GUJARAT TECHNOLOGICAL UNIVERSITY
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BE - SEMESTER-III (OLD) EXAMINATION — WINTER 2018
Date: 28/11/2018
Subject Name: Electrical Drives And Controls
Time: 10:30 AM TO 01:00 PM
Instructions:
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- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
Q.1 (a) Explain the classes of motor duty in details. [07]
(b) What is an electrical drive? Draw and explain the block diagram of electrical drives. Also write down its advantages? [07]
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Q.2 (a) Write a short note on various characteristic of DC shunt motor [07]
(b) A 4-pole, 240 V, wave connected shunt motor gives 11.19 kW when running at 1000 rpm and drawing armature and field currents of 50 A and 1.0 A respectively. It has 540 conductors and its resistance is 0.1 ohms. Assuming a drop of 1 Volt per brush, find (1) total torque (2) useful torque (3) useful flux/pole (4) rotational losses and (5) Efficiency [07]
OR
Q.2 (b) A 250 V shunt motor with armature resistance of 0.5 Q runs at 600 r.p.m on full load and takes an armature current of 20A. If resistance of 1.0 Q is placed in the armature circuit, find the speed at (i) full load torque (ii) half full load torque. [07]
Q.3 (a) State and explain the different classes of Squirrel cage motor. [07]
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(b) Explain Split phase & Shaded pole Induction motor with a neat sketch. [07]OR
Q.3 (b) Describe in detail the braking of DC shunt motor with neat sketch. [07]
Q.4 (a) Explain Autotransformer starter with neat-diagram [07]
(b) What is the need of starter in DC motor? Explain 3-point starter with diagram [07]
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OR
Q.4 (b) Explain the Ward-Leonard speed control method? [07]
Q.5 (a) Explain the speed control methods of three phase induction motor by (1) Stator voltage control (2) Frequency control [07]
(b) Explain the different slip power recovery schemes? [07]
OR
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Q.5 (a) Explain types-of Choppers with neat sketch. [07]
(b) Explain Single phase Full bridge inverter with Resistive load [07]
OR
Q.5 (b) Explain V/F control for AC drives. [07]
(a) Explain Single phase Half wave controlled rectifiers with Resistive load. [07]
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Total Marks: 70
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