1
GATE EE 1998
MCQ (Single Correct Answer)
+1
-0.3
A 3-phase squirrel cage induction motor has a full load efficiency of 0.8 and a maximum efficiency of 0.9. It is operated at a slip of 0.6 by applying a reduced voltage. The efficiency of the motor at this operating point is:
A
less than 0.4
B
greater than 0.6
C
in the range of 0.8 $$\pm$$ 0.1
D
None of the above
2
GATE EE 1998
MCQ (Single Correct Answer)
+2
-0.6
A 50 Hz transformer having equal hysteresis and eddy current losses at rated excitation is operated at 45 Hz at 90% of its rated voltage. Compared to rated operating point, the core losses under this condition:
A
reduce by 10%
B
reduce by 19%
C
reduce by 14.5%
D
remain unchanged
3
GATE EE 1998
MCQ (Single Correct Answer)
+1
-0.3
A synchronous generator connected to an infinite bus is overexcited. Considering only the reactive power, from the point of view of the system, the machine acts as
A
a capacitor
B
an inductor
C
a resistor
D
None of the above
4
GATE EE 1998
MCQ (Single Correct Answer)
+2
-0.6
The armature of a single phase alternator is completely wound with T single turn coils distributed uniformly. The induced voltage in each turn is 2 Volts (rms). The emf of the whole winding is
A
2 T volt
B
1.11 T volt
C
1.414 T volt
D
1.273 T volt
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