Torque-Slip Characteristics in Three Phase Induction Motor - MCQs with Answers

Torque-Slip Characteristics in Three Phase Induction Motor - MCQs with Answers

Q1. A 400v, 4 pole, 3 phase, 50 Hz star connected induction motor has a rotor resistance and reactance per phase equal to 0.02 ohm and 0.2 ohm respectively. Then the slip at which maximum torque occurs and the corresponding maximum torque is (assuming stator to rotor turns ratio as 6)

a. 10%, 159.08 N-m
b. 20%, 318.16 N-m
c. 11%, 159.08 N-m
d. 10%, 318.16 N-m

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Q2. When an induction motor is loaded from no load to full load, its speed and slip will

a. Increases, decreases
b. Decreases, increases
c. Both increases
d. Both decreases

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Q3. An induction motor when loaded from no load to full load, its slip also varies from s=1 to s=0. Then the torques in the low slip region and in high slip region is

a. Both are directly proportional to the slip
b. Both are inversely proportional to the slip
c. Directly proportional to the slip, inversely proportional to the slip
d. Independent of slip, proportional to the slip

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Q4. The curve obtained by plotting torque against slip from s=1 to s=0 is called torque slip characteristics. The nature of the graph in the low slip region and in the high slip region is

a. Rising exponential, decaying exponential
b. Both will be straight line
c. Straight line, rectangular parabola
d. Straight line, decaying exponential

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Q5. If an induction motor is operating at a point in the high slip region, then the motor will be

a. Stable
b. Unstable
c. Either stable or unstable depending on the torque
d. None of these

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Q6. The value of slip for motoring, generating and braking region respectively are

a. S > 1, 0 = s = 1, s < 0
b. S < 0, 0 = s = 1, s > 1
c. 0 = s = 1, s > 1, s < 1
d. 0 = s = 1, s < 0, s > 1

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Q7. When the slip of an induction machine is negative, it is running as a

a. Motor
b. Generator
c. Synchronous machine
d. None of these

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