University of Mumbai 2007-7th Sem B.E Electrical and Electronics Engineering Electrical Drives & Control Old - Question Paper
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Con. 4935-07. eUd>l'<*J Sf fpyzLdJ CD-6855.
(OLD COURSE) J
( 3 Hours) [ Total Marks ; 100
N.B. (1) Question No. 1 is compulsory.
(2) Attempt any four questions out of remaining six questions.
(3) Assume any suitable data, if required.
1. (a) Explain four quadrant operation of electrical drive. 10 (b) Explain the block diagram of an electrical drives. What are the functions of power modulators ? 10
2. (a) What arc the different types of load torques ? Explain with examples and its speed torque 10
characteristics.
(b) What are the different types of speed control methods of 3~phase induction motor ? Explain 10 any two.
**. (a) A drive has following parameters J = 10 kg-mz, I = 100 - 0-1 N, load torque 10 (Tl) Tl = 0*05 N where N is in rpm.
Initially, the drive is operating in steady state. Now it is to be reversed for this motor characteristics is changed to T = - 10D - 0-1 N. Calculate the time of reversal. (Torques are in Nm).
(b) Explain the principle of operation of Phase-Locked-Loop (PLL) control. 10
4. (a) Explain Dynamic Braking of D.C. motor.
(b) Explain the principle of slip power recovery. Explain with neat diagram static scherbius 10 drive.
5. (a) A 200 V d.c. series motor runs at 950 r.p.m. and takes an armature current of 90 A. It is 12
operated under dynamic braking at twice the rated torque and 800 r.p.m. Calculate the value of braking current and braking resistor.
(b) Explain the different types of drive circuits for stopper motors. B
6. (a) A 220 V, 950 r.p.m., 90 A d.c. separately excited motor has an armature resistance of 12
0*05 ohm. It Is braked by plugging from an initial speed of 1050 r.p.m. Calculate :
(i) resistance to be placed in armature circuit to limit braking current to twice the full load value.
(ii) Braking torque.
(b) Explain Load equalisation* 6
7. Explain any two : 20
(a) Steady state stability
(b) Selection of motor power rating
(c) Controlled rectifier fed d.c. drive.
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