1
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
2
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
3
GATE EE 2005
MCQ (Single Correct Answer)
+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
4
GATE EE 2004
MCQ (Single Correct Answer)
+2
-0.6
A single-phase, 230 V, 50 Hz, 4 pole, capacitor-start induction motor has the following stand still impedances
Main winding Zm =6.0 + j4.0Ω
Auxiliary winding Za = 8.0 + j6.0Ω
The value of the starting capacitor required to produce 90° phase difference between the currents in the main and auxiliary windings will be
A
176.84 µF
B
187.24 µF
C
265.26 µF
D
280.86 µF

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