Kurukshetra University 2007 B.Tech Electronics and Communications Engineering Electomechanical Energy Conversions - Question Paper

Electromechanical Energy Conversion Paper
ELE-201E
Optional (1)
Time: 3 Hours
Maximum Marks: 100

Note:—Attempt any 5 ques..

1.(a) State Faraday's laws of electro-magnetic induction and discuss how it is applied for working of a d.c. motor. [10]

(b) explain the different kinds of Losses in magnetic circuits. [10]

2.(a) Draw the no-load phasor diagram of a transformer and derive expression for magnetizing and core-loss components of no-load current. [10]

(b) describe the voltage regulation of a transformer. Deduce the expression for the voltage regulation. [10]

3.(a) What is an electromechanical conversion device ? discuss the working of a generator with the help of a power flow diagram. [10]

(b) discuss how torque is produced in a rotating electrical machine. What do you understand by torque angle ? [10]

4.(a) Derive the expression for generated emf in a d.c generator. describe all the symbols with their units. [10]

(b) explain the effects of armature reaction in a d.c. generator. [10]

5.(a) What is meant by back emf ? Is the back emf greater or lesser than the applied voltage ? Why ? By what amount do the 2 voltage differ ? [10]

(b) explain the flux central method for the speed of a shunt motor. [10]

6. explain the point of similarities betweeh a transformer and an induction motor. Hence, discuss why an induction machine is call a generalized transformer ? Why an induction motor, at no-load,operates at a very low power factor ? [20]

7.(a) Draw the torque-speed characteristics of polyphase induction motor and clearly indicate the effect of change in rotor resistance. [10]

(b) discuss the terms slip, slip frequency, wound rotor and cage rotor. [10]



8. Write short notes on the following:—

(a) Starting of Synchronous motor. [10]
(b) Curves of Synchronous motor. [10]

Earning:   Approval pending.