RRB/SSC JE Electrical 2019 || Three Phase Induction Motors Quiz 3

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Question 1

A 3-phase induction motor is connected to a supply of normal voltage. The e.m.f. induced between the slip rings at standstill is and the resistance and standstill reactance/phase are and respectively. The rotor is joined to a star-connected resistance of /phase. The rotor phase current at starting will be

• A
• B
• C
• D

Question 2

A 3-phase, 6-pole squirrel -cage induction motor operates at a full-load slip of 4% when rated voltage and rated frequency are applied. The speed of rotation of the stator m.m.f. is

• A
• B
• C
• D

Question 3

In the above question, what is the full-load speed?

• A
• B
• C
• D

Question 4

In an induction motor, if air gap is increased, its

• Aspeed will reduce
• Bpower factor will decrease
• Cefficiency will improve
• Dspeed will increase

Question 5

The rotor slots are slightly skewed in the squirrel-cage induction motor to

• Areduce motor noise and vibration
• Breduce starting current
• Cincrease rotor resistance due to increased length of rotor bars
• Dall of the above

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