1
GATE EE 2007
MCQ (Single Correct Answer)
+2
-0.6
A three phase squirrel cage induction motor has a starting current of seven times the full load current and full load slip of $$5\% $$

If a star-delta starter is used to start this induction motor, the per unit staring torque will be

A
$$0.607$$
B
$$0.816$$
C
$$1.225$$
D
$$1.616$$
2
GATE EE 2007
MCQ (Single Correct Answer)
+2
-0.6
A three phase squirrel cage induction motor has a starting current of seven times the full load current and full load slip of $$5\% $$

If an auto-transformer is used for reduced voltage starting to provide $$1.5$$ per unit starting torque, the auto-transformer ratio $$\left( \% \right)$$ should be

A
$$57.77\% $$
B
$$72.56\% $$
C
$$78.25\% $$
D
$$81.33\% $$
3
GATE EE 2007
MCQ (Single Correct Answer)
+2
-0.6
A three-phase squirrel cage induction motor has a starting torque of $$150\% $$ and a maximum torque of $$300\% $$ with respect to rated torque at rated voltage and rated frequency. Neglect the stator resistance and rotational losses. The value of slip for maximum torque is
A
$$13.48\% $$
B
$$16.42\% $$
C
$$18.92\% $$
D
$$26.79\% $$
4
GATE EE 2007
MCQ (Single Correct Answer)
+2
-0.6
A single-phase $$50$$ $$kVA,$$ $$250$$ $$V/500V$$ two winding transformer has an efficiency of $$95\% $$ at full load, unity power factor. If it is reconfigured as a $$500V/750V$$ auto-transformer, its efficiency at its new rated load at unity power factor will be
A
$$95.752\% $$
B
$$97.851\% $$
C
$$98.276\% $$
D
$$99.241\% $$
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