ட்‌ /22

74.

75.

76.

7೫

78.

Which of the following techniques can be used for speed control of three phase squirrel
cage induction motor ?
i. Rotor resistance control.

ர்‌. V/f control.

iii. Pole changing method.

A) Only i and ii B) Only i and iii
C) Only ii 0) Only ii and iii

Which of the following statements is/are true regarding star delta starter of three phase
induction motor ?

i. At the time of starting the windings are connected in star and after attaining the
steady state speed the windings are connected in delta.
ii. At the time of starting the windings are connected in delta and after attaining the
steady state speed the windings are connected in star.
iii. It reduces the starting torque to one third of that produced by direct switching in
delta.
iv. It increases the starting torque to three times of that produced by direct switching in
delta.
A) Only i and iii B) Only ii and iii
C) Only i and iv D) Only ii and iv

The number of slip rings in a star connected three phase alternator with the field provided
on rotor is

A)3 B) 4 02 0) 5

The armature reaction effect in a three phase alternator operating in isolated condition
depends on which of the following ?
i. Power factor of the load.
ii. Speed of the machine.
iii. Load current.
A) Only i and ॥| B) Only ii and iii
©) Onlyi D) Only iii

Which of the follawing statement/statements are true regarding damper winding in a three
phase synchronous motor ?

i, Damper winding helps to start the motor.

ர்‌. Current is present in damper winding when the motor is running at synchronous
speed.

iii. Current is zero in damper winding when the motor is running at synchronous
speed.

A) Only iii 8) Only i and ii ©) Only i D) Only i and iii

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