University of Mumbai 2007-7th Sem B.E Electrical and Electronics Engineering Electrical Drives & Control Old - Question Paper
wt Miy 0?-92
Con. 2261-07. (OLD COURSE) ND-7997
(3 Hours) [Total Marks : 100 *
N.B.: (1) Question No. 1 Is compulsory.
(2) Attempt any four out of remaining six questions.
(3) Assume any suitable data wherever required but justify the same.
1. (a) Explain the block diagram of an electrical drive. What are the functions of power 10
moQulator ?
(b) What Is steady stale stability ? Explain with examples. 10
2. (a) What is load equalisation and why it is required ? 10 (b) Explain the different drive circuits for stepper motors. 10
3. (a) A 200 V, 10 A, 1900 rpm shunt motor has the armature and field resistance of 10
C*5 and 400 ohms respectively. It drives a load whose torque is constant at rated torque. Calculate motor speed if the source voltage drops to 170 V.
(b) Explain with block diagram the operation of Phase-Locked Loop (PLL) control. 10
4. Write short notes on :
(a) Types of load torques 6
(b) Dynamic Braking of DC motor 8
(c) Textile mills. 6
5. (a) Explain four quadrant operation of electrical drive. 10 (b) A 220 V, 1000 rpm, 100 A d.c. seperately excited motor has an armature resistance 10
of 0-05 ohm. It is braked by plugging from an initial speed of 1050 rpm. Calculate :
(i) Resistance to be placed in armature circuit to limit braking current to twice the full load valve.
(ii) Braking torque.
6. (a) Name the different methods of speed control of three phase Induction motor and 10
explain any two.
(b) The 10 minute rating of a motor used in a domestic mixer is 200 watts. The heating 10 time constant is 40 min. and the maximum efficiency occures at full load (continuous). Determine the continuous rating. Derive the formula used.
7. Writ short notes on : 20
(a) Advantages of Electrical drives
(b) Selection of motor power rating
(c) Static Scherbius drive
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