1
GATE EE 1997
Fill in the Blanks
+2
-0
A single-phase alternator has a synchronous reactance of $$2$$ $$ohms$$ and negligible resistance. If it supplies $$10$$ $$A$$ to a purely capacitive load at $$200V,$$ then generated $$e.m.f$$ will be ... $$V$$ and the regulation will be ...... $$\%$$
2
GATE EE 1993
+2
-0.6
A three phase alternator has negligible stator resistance. A short circuit test is conducted on this alternator. At a particular speed a field current of $${{\rm I}_f}$$ is required to drive the rated armature current. If the speed of the alternator is reduced to half, the field current required to maintain rated armature current
A
would be equal to $${{\rm I}_f}$$
B
would be equal to $$2$$ $${{\rm I}_f}$$
C
would be equal to $${{\rm I}_f}/2$$
D
cannot be predicted due to insufficient data
3
GATE EE 1993
+2
-0.6
A synchronous motor operates at $$0.8$$ $$p.f.$$ lagging. If the field current of the motor is continuously increased

$$(1)$$ the power factor decreases upto a certain value of field current and thereafter it increases
$$(2)$$ the armature current increases upto a certain value of field current and thereafter it decreases
$$(3)$$ the power factor increases upto a certain value of field current and thereafter it decreases
$$(4)$$ the armature current decreases upto a certain value of field current and thereafter it increases. From these the correct one is

A
$$1,2$$
B
$$2,3$$
C
$$3,4$$
D
$$1,3$$
4
GATE EE 1993
+2
-0.6
Two $$550$$ $$kVA$$ alternators operate in parallel to supply the following loads
$$(i)$$ $$250$$ $$kW$$ at $$0.95$$ power factor lag
$$(ii)$$ $$100$$ $$kW$$ at $$0.8$$ power factor lead one machine is supplying $$200kW$$ at $$0.9$$ power factor lag. The power factor of the other machine must be

A
$$0.89$$ lead
B
$$0.95$$ lead
C
$$0.95$$ lag
D
$$0.89$$ lag
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