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Register Number
SATHYABAMA UNIVERSITY
(Established under section 3 of UGC Act,1956)
Course & Branch :B.E - P-EEE
Title of the Paper : Electrical Machines – II
Sub. Code : 614PT202 (2009-2010)
Date :16/11/2012
Max. Marks:80
Time : 3 Hours
Session :AN
_______________________________________________________________________________________________________________________________
1.
PART - A
(10 x 2 = 20)
Answer ALL the Questions
What are the conditions to be satisfied for successful parallel
operation of alternators?
2.
List the difference between salient pole and cylindrical rotor
synchronous machines.
3.
What are the causes if a synchronous motor fails to start?
4.
What is V and Inverted V curve .Why it is called so.
5.
What are the different speed control methods available for 3
phase slip ring Induction motor?
6.
Name any two starters used for induction motors.
7.
What will be reasons if a single phase Induction motor fails to
start and hums loudly?
8.
State any two applications of Universal motor.
9.
Write the expression for 3-phase torque of a permanent magnet
synchronous motor.
10. What is two-phase servomotor?
PART – B
Answer All the Questions
(5 x 12 = 60)
11. Discuss the data required for estimating the regulation of
alternator by potier method .Explain how regulation is calculated
for various power factor.
(or)
12. Find the synchronous impedance and reactance of an alternator in
which a given field current produces an armature current of 200
A on short circuit and a generated e.m.f of 50 V on open circuit.
The armature resistance is 0.1 ohm. To what induced voltage
must the alternator be excited if it is to deliver a load of 100 A at
a pf of 0.8 lagging, with a terminal voltage of 200 V.
13. Explain the effect of varying excitation upon the armature current
and power factor of the synchronous motor for a constant output
with phasor diagram.
(or)
14. (a) A 500, 1 Phase synchronous motor gives a net output
mechanical power of 7.46 KW and operates at 0.9 pf lagging. Its
effective resistance is 0.8 ohm. If the iron and friction losses are
500 W and excitation losses are 800 W, estimate the armature
current .calculate the commercial efficiency.
(b) A 75 KW,3 phase star connected ,50 Hz ,440v cylindrical
rotor synchronous motor operates at rated condition with 0.8 pf
leading. The motor efficiency excluding field and stator losses, is
95% and Xs =2.5 ohm. Calculate 1.mechanical power developed
2.armature current 3.Back e.m.f 4.power angle 5.Maximum or
pull out torque of the motor.
15. Draw the circle diagram for a 5.6 KW, 400V, 3 phase, 4 pole, and
50HZ slip ring induction motor from the following data:
No load test: 400 V, 6A, cos φ0=0.087.
Short circuit test: 100V, 12A, 720W.
The ratio of primary to secondary terms is 2.62.Stator resistance
per phase is 0.67 OHM and that of the rotor is 0.185 OHM
.Calculate i) The full load current ii) Full load slip iii) Full load
power factor iv) Maximum power and v)Maximum Torque.
(or)
16. Explain the construction, types and rotating magnetic principle of
3 phase Induction motor.
17. Explain the construction, principle, characteristics
applications of split phase type induction motor.
(or)
18. Explain the construction, principle, characteristics
applications of reluctance type induction motor.
and
and
19. Explain the construction & principle of operation of permanent
magnetic synchronous motor.
(or)
20. Draw the speed torque characteristics and phasor diagrams of
permanent magnetic synchronous motor and explain.