SKR Engineering College 2007 B.E Electrical and Electronics Engineering EE 1213 – ELECTRICAL DRIVES AND CONTROL - Question Paper

SKR ENGINEERING COLLEGE

DEPARTMENT OF ELECTRICAL& ELECTRONICS ENGG
III SEM- MECHANICAL ENGG
EE 1213 – ELECTRICAL DRIVES AND CONTROL

MODEL exam

DATE: 09.11.06 MAXIMUM MARKS: 100
TIME: three Hrs

PART –A (10 x two =20)


1. Mention the basic kinds of electrical drives?
2. What is meant by intermittent loading?
3. What is plugging?
4. Draw the speed-torque characteristics of D.C shunt motor?
5. What is the need of the starter?
6. Name the various starters used in D.C motors?
7. Why is the single-phase induction motor not self starting??
8. Write the speed formula of a dc motor?
9. How is chopper used in speed control of dc motor?
10. Define inverters?

PART –B (5 x 16=80)


11.a) Derive the expression for the heating time constant and draw the heating and cooling curves. (16)

(OR)

b) (i).What factors govern the selection of a motor for a particular application?(8)

. (ii) discuss the loading of an electric motor and its duty cycle with sample diagram. (8)


12.a) (i) Draw the speed torque characteristics of DC motor (8)
(ii) A dc shunt motor drives a centrifugal pump whose torque varies as the square of the speed. The motor is fed from a 200V supply and takes 50A when running at 1000 rpm. What resistance must be inserted in the armature circuit in order to decrease the speed to 800 rpm? The armature and field resistance of the motor are 0.1ohm and 200ohm respectively. (8)

(OR)

b) (i). discuss the conditions to achieve electric regenerative breaking. (8)

(ii) discuss the methods of breaking used in induction motor. (8)


13.a) (i). With the neat sketch draw and discuss the 4-point starter along with the protective device. (8)
(ii). discuss any 1 kind of starter used in cage induction motors with the neat sketch. (8)

(OR)

b) (i). define ward Leonard speed control. (10)
(ii). Mention its advantages and disadvantages. (6)


14.a)(i) discuss the field control methods used for D.C series motor for speed control?(8)
(ii) A 250V dc series motor takes 40 ampere of current when developing a full load torque at 1500rpm. Its resistance is 0.5 ohm. If the load torque varies as the square of the speed determine the resistance to be connected in series with the armature to decrease the speed to 1200 rpm. presume that the flux is proportional to the field current. (8)

(OR)

b) discuss clearly with diagrams thyrister control on dc side or chopper control on dc series motor. (16)


15.a) (i). discuss any two-speed control methods employed in dc shunt motor? (8)
(ii) define slip power recovery schemes? (8)

(OR)


b) discuss the various methods of solid-state speed control of three-phase induction motor?(16)

Earning:   Approval pending.