SKR Engineering College 2006 B.E Electronics & Tele-Communication Engineering ELECTRICAL MACHINES - Question Paper

III SEM
EE 1211 – ELECTRICAL MACHINES

Maximum: 100 Marks
Duration: three Hrs

PART: A (2×10 = 20)

1.State the purpose of magnetic yoke in a DC machine
2.Why a starter is necessary for a DC motor?
3.What is the function of transformer?
4.Why the load current of a transformer increases, hoe does the input current increases to meet with the new condition.
5.In which kind of motor can resistance be introduced in the rotor circuit? What is the effect of it?
6.Is single-phase induction motor self starting? Why?
7.Write down any four advantages of short-pitch winding in synchronous machines.
8.Name the various kind of single phase synchronous motor
9.What are the major sources of energy used for generation of electrical power?
10.What are the major equipments used in the power station?

PART: B (5×16 = 80)

11.Explain the characteristics (performance and mechanical) of DC motor. List the applications of this motor (16)
(Or)
Draw the diagram of a 3-point and four point starter and identify the different parts. discuss the function of no-volt coil and over load release. (16)

12.Obtain the equivalent circuit of a single-phase transformer also draw the approximate equivalent circuit and identify the different parameters. (16)
(Or)
Draw the equivalent circuit for a single phase 1100/200V transformer on which the subsequent outcomes were found
a.1100V, 0.5A, 55W on primary side, secondary being open circuit.
b.10V, 80A, 400W on low voltage side, high voltage being short-circuited.
compute the voltage regulation and efficiency for the above transformer when supplying 100A at 0.8-pf lagging. (16)

13. a) discuss the torque Vs slip characteristics of slip ring 3-phase induction motor.
b) With the help of a neat sketch, define the principle of working of a star-delta starter for a 3-phase induction motor. Where it is used? (8)

(Or)
A 37.3 KW, four pole, 50Hz induction motor has friction and windage losses of 3320W. The stator losses equal the rotor losses. If the motor delivering full load power output at a speed of 1440 rpm, compute synchronous speed, slip, mechanical power developed by the motor, rotor copper loss, power transferred from stator to rotor, stator power input and efficiency. (16)

14.Derive the expression for voltage regulation of an alternator. define any method (synchronous or ampere turn method) to determine voltage regulation of synchronous generator. (16)
(Or)
a) discuss the principle and operation of hysteresis motor. (8)
b) elaborate the advantages of having stationary armature winding in 3-phase synchronous generator? (8)

15..a) discuss the generation, transmission and distribution structure of electric power system with all its components. (12)
b) List the different kinds of overhead line insulators and its applications.(4)
(Or)
a) discuss the advantages high voltage AC transmission with derivation. (12)
b) Write the short notes on EHVDC. Name the various kinds of HVDC links. (8)

Earning:   Approval pending.