RRB/SSC JE Electrical 2019 || Three Phase Induction Motors Quiz 1

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Question 1

If the speed of 3-phase induction motor increases, its efficiency

• Adecreases
• Bincreases
• Cremains the same
• Dinsufficient data

Question 2

The approximate efficiency of a 3-phase, 4-pole induction motor running at is…………………

• A90%
• B40%
• C65%
• Dnone of the above

Question 3

A four-speed squirrel cage induction motor uses………………….stator windings.

• Afour
• Bthree
• Cone
• Dtwo

Question 4

A 3-phase, 6-pole induction motor is connected to a supply. The voltage induced in the rotor bars is 4V when the rotor is at standstill. The voltage induced in the rotor bars at is

• A
• B
• C
• D

Question 5

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 phase current at starting when the rings are short-circuited is

• A
• B
• C
• D

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