1
GATE EE 2006
+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 2005
+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
3
GATE EE 2005
+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
4
GATE EE 2005
+2
-0.6

Assertion [a]: Under V/f control of induction motor, the maximum value of the developed torque remains constant over a wide range of speed in the subsynchronous region.

Reason [r]: The magnetic flux is maintained almost constant at the rated value by keeping the ratio V/f constant over the considered speed range.

A
Both [a] and [r] are true and [r] is the correct reason for [a]
B
Both [a] and [r] are true but [r] is not the correct reason for [a]
C
Both [a] and [r] are false
D
[a] is true but [r] is false
GATE EE Subjects
Electric Circuits
Electromagnetic Fields
Signals and Systems
Electrical Machines
Engineering Mathematics
General Aptitude
Power System Analysis
Electrical and Electronics Measurement
Analog Electronics
Control Systems
Power Electronics
Digital Electronics
EXAM MAP
Joint Entrance Examination