1
GATE EE 2006
MCQ (Single Correct Answer)
+2
-0.6
A $$3$$ phase, $$10$$ $$kW$$, $$400$$ $$V,$$ $$4$$ pole, $$50$$ $$Hz$$, star connected induction motor draws $$20$$ A on full load. Its no load and blocked rotor test data are given below.
No Load Test: $$400V$$ $$6A$$ $$1002W$$
Blocked Rotor Test: $$90V$$ $$15A$$ $$762W$$
Neglecting copper loss in No Load Test and core loss in Blocked Rotor Test, estimate motor's full load efficiency.
A
$$76\% $$
B
$$81\% $$
C
$$82.4\% $$
D
$$85\% $$
2
GATE EE 2006
MCQ (Single Correct Answer)
+1
-0.3
A synchronous generator is feeding a zero power factor (lagging) load at rated current the armature reaction is
A
magnetizing
B
demagnetizing
C
cross magnetizing
D
Ineffective
3
GATE EE 2006
MCQ (Single Correct Answer)
+2
-0.6
A $$3$$-phase $$4000$$ $$V,$$ $$5$$ $$kW,$$ star connected synchronous motor having an internal reactance of $$10$$ $$ohms$$ is operating at $$50\% $$ load, unity power factor. Now, the excitation is increased by $$1\% $$, what will be the new load in percent, if the power factor is to be kept same? Neglect all losses and consider linear magnetic circuit.
A
$$67.9\% $$
B
$$56.9\% $$
C
$$51\% $$
D
$$50\% $$
4
GATE EE 2006
MCQ (Single Correct Answer)
+2
-0.6
A $$4$$ pole, $$50$$ $$Hz,$$ synchronous generator has $$48$$ slots in which a double layer winding is house. Each coil has $$10$$ turns and is short pitched by an angle to $$36$$ degrees electrical. The fundamental flux per pole is $$0.025$$ $$Wb$$

The line to line induced $$emf$$, for a three phase star connection is approximately

A
$$808$$
B
$$888$$
C
$$1400$$
D
$$1538$$
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