1
GATE EE 2006
MCQ (Single Correct Answer)
+2
-0.6
A $$3$$ phase, $$4$$ pole, $$400$$ $$V,$$ $$50$$ $$Hz,$$ star connected induction motor has following circuit parameters $${r_1} = 1.0\Omega ,\,{r_2} = 0.5\Omega ,$$ $${\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {x_1} = x{'_2} = 1.2\Omega ,{\mkern 1mu} {x_m} = 35\Omega $$
The starting torque when the motor is started direct-on-line is (use approximate equivalent circuit model)
A
$$63.6$$ $$Nm$$
B
$$74.3$$ $$Nm$$
C
$$190.8$$ $$Nm$$
D
$$222.9$$ $$Nm$$
2
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
$$85\% $$
3
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
4
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
$$50\% $$
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