Electrical Machines Questions and Answers – Induction Machines
Operating Characteristics of Induction Motors
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A 10 kW, 400 V, 3phase, 4pole, 50 Hz induction motor develops the rated output at rated voltage with its slip rings shorted.
The maximum torque is twice the full load torque occurs at the slip of 10% with zero external resistance in the rotor circuit.
An external resistance is now tripled in the rotor circuit. Then the slip at which maximum torque occur for the same load torque is
The maximum torque is twice the full load torque occurs at the slip of 10% with zero external resistance in the rotor circuit.
An external resistance is now tripled in the rotor circuit. Then the slip at which maximum torque occur for the same load torque is
Correct!
Wrong!

A 10 kW, 400 V, 3phase, 4pole, 50 Hz induction motor develops the rated output at rated voltage with its slip rings shorted.
The maximum torque equal to twice the full load torque occurs at the slip of 10% with zero external resistance in the rotor circuit.
The slip at the full load torque will be
The maximum torque equal to twice the full load torque occurs at the slip of 10% with zero external resistance in the rotor circuit.
The slip at the full load torque will be
Correct!
Wrong!

The stable point to use the induction motor possesing the below characteristic.
Correct!
Wrong!

A 3phase, 50 Hz, 6pole induction motor has a shaft output of 10kW at 930 rpm. Friction and windage losses is 1% of the output.Total stator losses is 600W.
The rotor input is
The rotor input is
Correct!
Wrong!

Slip vs the torque developed in an induction motor is given as
Correct!
Wrong!

The power factor variation of the 3phase induction motor is given by
Correct!
Wrong!

A 10 kW, 400 V, 3phase, 4pole, 50 Hz induction motor develops the rated output at rated voltage with its slip rings shorted.
The maximum torque is twice the full load torque occurs at the slip of 10% with zero external resistance in the rotor circuit.
The speed at the full load torque will be
The maximum torque is twice the full load torque occurs at the slip of 10% with zero external resistance in the rotor circuit.
The speed at the full load torque will be
Correct!
Wrong!

Mark the stable operating point when the load torque shifts from Tl1 to Tl2.
Correct!
Wrong!

The speedpower output characteristic of a 3phase induction motor is
Correct!
Wrong!

At which point shall the induction machine be operated to attain a stable operation?
Correct!
Wrong!

A 3phase, 50 Hz, 6pole induction motor has a shaft output of 10kW at 930 rpm. Friction and windage losses is 1% of the output.Total stator losses is 600W.
The rotor input is
The rotor input is
Correct!
Wrong!

Introducing the external resistance increases
(i) speed
(ii) output power
(iii) starting torque
(i) speed
(ii) output power
(iii) starting torque
Correct!
Wrong!

Introducing the external resistance decreases
(i) speed
(ii) output power
(iii) starting torque
(i) speed
(ii) output power
(iii) starting torque
Correct!
Wrong!

The stator current of the induction motor is given by which of the below?
Correct!
Wrong!

A 10 kW, 400 V, 3phase, 4pole, 50 Hz induction motor develops the rated output at rated voltage with its slip rings shorted. The maximum torque is twice the full load torque occurs at the slip of 10% with zero external resistance in the rotor circuit. An external resistance is now tripled in the rotor circuit. Then the stator current will
Correct!
Wrong!

For a three phase induction motor, maximum torque is double the full load torque and starting torque is 1.6 times the full load torque. To get a full load slip of 5%, percentage reduction in the rotor resistance should be
Correct!
Wrong!

The stable point in the operation of the induction motor is
Correct!
Wrong!

Four students had been conducting conducting experiments on the same induction motor for its efficiency characteristics. Which student has taken the best results?
Correct!
Wrong!

Operating (or Performance) Characteristics of Induction Motors