1
GATE EE 2006
MCQ (Single Correct Answer)
+2
-0.6
The speed of a $$4$$-pole induction motor is controlled by varying the supply frequency while maintaining the ratio of supply voltage to supply frequency $$(V/f)$$ constant. At rated frequency of $$50$$ $$Hz$$ and rated voltage of $$400$$ $$V$$ its speed is $$1440$$ $$rpm$$. Find the speed at $$30$$ $$Hz,$$ if the load torque is constant
A
$$882$$ $$rpm$$
B
$$864$$ $$rpm$$
C
$$840$$ $$rpm$$
D
$$828$$ $$rpm$$
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 2005
MCQ (Single Correct Answer)
+2
-0.6
Under no load condition, if the applied voltage to an induction motor is reduced from the rated voltage to half the rated value,
A
the speed decreases and the stator current increases
B
both the speed and the stator current decrease
C
the speed and the stator current remain practically constant
D
there is negligible change in the speed but the stator current decreases
4
GATE EE 2005
MCQ (Single Correct Answer)
+2
-0.6
A three-phase cage induction motor is started by direct-on-line (DOL) switching at the rated voltage. If the starting current drawn is 6 times the full load current, and the full load slip is 4%, the ratio of the starting developed torque to the full load torque is approximately equal to
A
0.24
B
1.44
C
2.40
D
6.00
GATE EE Subjects
EXAM MAP