ELECTRICAL MACHINES-II (QUIZ-1)

In the 3-phase induction motor, the resultant flux is of a constant nature and is

• equal to φ_m, where φ_m is the maximum flux due to any phase

• 3/2 times maximum value of flux due to any phase

• 1/2 times maximum value of flux due to any phase

• 3 times maximum value of flux due to any phase

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

• provide ease of fabrication.

• reduce the magnetic hum and locking tendency of rotor.

• increase the strength of rotor bars.

• decrease the amount of copper to be used.

What is the frequency of rotor current of 50 Hz induction motor operating at 4% slip?

• 50Hz

• 2.5Hz

• 1 Hz

• 2HZ

A 3-phase 6 pole 50 Hz induction motor is running at 5% slip.What is the speed of the motor?

•  1000 rpm

• 900 rpm

• 950 rpm

• 850 rpm

An 8-pole, 3-phase, 50 Hz induction motor is operating at a speed of 720 rpm. The frequency of the rotor current of the motor in Hz is __________

• 2

• 4

• 3

• 1

 In terms of slip, the actual speed (N) of the induction motor can be expressed as

• N_s (1-s)

• N_s (s-1)

• N_s / (1-s)

• N_s / (s-1)

An induction motor works with

• DC only

• AC Only 

• Both AC & DC

• None of these

The stator core of a 3- phase induction motor is laminated in order to reduce the

• Eddy current loss

• Hysteresis loss

• Both eddy current and hysteresis I loss

• Weight of the stator

The induction motor shaft should be

• Hollow

• Stiff

• Flexible

• Any of these

In a 3-phase squirrel cage induction motor

• Rotor conductors are short circuited through end rings

• Rotor conductor ends are short circuited through slip rings

• Rotor conductors are kept open

• None of the above