1
GATE EE 2014 Set 2
MCQ (Single Correct Answer)
+1
-0.3
In a constant V/f control of induction motor, the ratio V/f is maintained constant from 0 to base frequency, where V is the voltage applied to the motor at fundamental frequency f. Which of the following statements relating to low frequency operation of the motor is TRUE?
A
At low frequency, the stator flux increases from its rated value.
B
At low frequency, the stator flux decreases from its rated value.
C
At low frequency, the motor saturates.
D
At low frequency, the stator flux remains unchanged at its rated value.
2
GATE EE 2014 Set 2
MCQ (Single Correct Answer)
+1
-0.3
A three-phase, 4-pole, self excited induction generator is feeding power to a load at a frequency $$f_1$$. If the load is partially removed, the frequency becomes $$f_2$$. If the speed of the generator is maintained at 1500 rpm in both the cases, then
A
$$f_1,f_2$$ > 50Hz and $$f_1$$ > $$f_2$$
B
$$f_1$$ < 50Hz and $$f_2$$ > 50Hz
C
$$f_1,f_2$$ < 50Hz and $$f_2$$ > $$f_1$$
D
$$f_1$$ > 50Hz and $$f_2$$ < 50Hz
3
GATE EE 2014 Set 2
MCQ (Single Correct Answer)
+2
-0.6
A three-phase slip-ring induction motor, provided with a commutator winding, is shown in the figure. The motor rotates in clockwise direction when the rotor windings are closed. GATE EE 2014 Set 2 Electrical Machines - Induction Machines Question 31 English If the rotor winding is open circuited and the system is made to run at rotational speed fr with the help of prime-mover in anti-clockwise direction, then the frequency of voltage across slip rings is f1 and frequency of voltage across commutator brushes is f2. The values of f1 and f2 respectively are
A
f + fr and f
B
f - fr and f
C
f - fr and f + fr
D
f + fr and f - fr
4
GATE EE 2014 Set 2
MCQ (Single Correct Answer)
+2
-0.6
A $$20$$-pole alternator is having $$180$$ identical stator slots with $$6$$ conductors in each slot. All the coils of a phase are in series. If the coils are connected to realize single-phase winding, the generated voltage is $${V_1}.$$ If the coils are reconnected to realize three-phase star-connected winding, the generated phase voltage is $${V_ 2}.$$ Assuming full pitch, single-layer winding, the ratio $${V_1}/{V_2}$$ is
A
$${1 \over {\sqrt 3 }}$$
B
$${1 \over 2}$$
C
$${\sqrt 3 }$$
D
$$2$$
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