1
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
2
GATE EE 2005
MCQ (Single Correct Answer)
+2
-0.6
In a single phase induction motor driving a fan load, the reason for having a high resistance rotor is to achieve
A
low starting torque
B
quick acceleration
C
high efficiency
D
reduced size
3
GATE EE 2005
MCQ (Single Correct Answer)
+1
-0.3
In relation to the synchronous machines, which one of the following statements is false?
A
In salient pole machines, the direct-axis synchronous reactance is greater than the quadrature-axis synchronous reactance
B
The damper bars help the synchronous motor self-start
C
Short circuit ratio is the ratio of the field current required to produce the rated voltage on open circuit to the rated armature current
D
The V-curve of a synchronous motor represents the variation in the armature current with field excitation, at a given output power
4
GATE EE 2005
MCQ (Single Correct Answer)
+2
-0.6
A $$1000$$ $$kVA,$$ $$6.6$$ $$kV,$$ $$3$$-phase star connected cylindrical pole synchronous generator has a synchronous reactance of $$20\Omega .$$ Neglect the armature resistance and consider operation at full load and unity power factor.

The induced $$emf$$ is close to (line to line)

A
$$5.5$$ $$kV$$
B
$$7.2$$ $$kV$$
C
$$9.6$$ $$kV$$
D
$$12.5$$ $$kV$$
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