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MCQs 1: The performance of induction motor is effected by the harmonics in the

Space variation of impressed voltage Time variation of impressed voltage Space variation of impressed current Time variation of impressed current
Answer Explanation

MCQs 2: The tooth or slot harmonics in an induction motor is caused due to

Variation of air gap reluctance Leakage flux Non sinusoidal nature of input voltage None of these
Answer Explanation

MCQs 3: The air gap flux of induction motor does not contain

2nd harmonics 3rd harmonics 5th harmonics 7th harmonics
Answer Explanation

MCQs 4: A 50 Hz, 3 phase induction motor with 4 pole stator is supplied by mains, which contains a pronounced fifth time harmonic. The speed of the fifth space harmonic will be

100 rpm 300 rpm 600 rpm 7500
Answer Explanation

MCQs 5: Crawling in an induction motor is caused

During starting of an induction motor At the fraction of rated speed Due to insulation failure All of these
Answer Explanation

MCQs 6: Cogging in an induction motor is caused

If the number of stator slots are integral multiple of rotor slots If the motor is running at fraction of its rated speed Due to fifth harmonic All of these
Answer Explanation

MCQs 7: Crawling is a phenomena mainly associated with

3rd harmonic 5th harmonic 7th harmonic 2nd harmonic
Answer Explanation

MCQs 8: What happens if the number of stator slots in an induction motor is equal to the number of rotor slots or integral multiple of rotor slots?

Motor will run at very high speed Motor will run at very low speed Motor will fail to start Does not get effected
Answer Explanation

MCQs 9: The crawling and cogging is not predominant in

Slip ring induction motor Squirrel cage induction motor Both (a) and (b) None of these
Answer Explanation

MCQs 10: The Y - axis and X - axis in a circle diagram represents

Voltage and current Current and power Power and voltage Current and voltage
Answer Explanation

MCQs 11: The circle diagram can be used to

Predict the performance of an induction motor under various load condition Find losses in an induction motor Efficiency of an induction motor All of these
Answer Explanation

MCQs 12: For plotting circle diagram no load power factor is required. The value of no load power factor will be

Lesser than 0.5 Greater than 0.5 Equal to 0.5 1
Answer Explanation

MCQs 13: For conducting no load test on an induction motor two wattmeter’s are required. Readings of the meters

Both will be positive One will be positive and other will be negative Both will be negative None of these
Answer Explanation

MCQs 14: In the blocked rotor tests, slip is equal to

0 1 0.5 0.707
Answer Explanation

MCQs 15: In a slip ring induction motor, the rotor resistance is

High during starting and low at normal operating speed Low at starting and high at normal operating speed Remains same during starting and normal operating speed None of these
Answer Explanation

MCQs 16: Deep bar or double cage rotors are used in squirrel cage induction motor to obtain

High starting current High starting torque Reduced starting current Reduced rotor resistance
Answer Explanation

MCQs 17: Deep bar or double cage rotors make use of skin effect. The skin effect depends upon

Nature of material Diameter of wire Shape of wire and frequency All of these
Answer Explanation

MCQs 18: In deep bar induction motor, the rotor consists of deep bars, short circuited by two end rings one on each side. The leakage inductance of bottom strip

Greater than that of top strip Lesser than that of top strip Equal to that of top strip None of these
Answer Explanation

MCQs 19: The skin effect in a deep bar induction motor is maximum when rotor is

At standstill Running at its maximum speed Running at no load Running at half load
Answer Explanation

MCQs 20: In double cage induction motor, the rotor consists of two cages or two layers of bars short circuited by end rings. The upper cage and lower cage respectively has

High resistance and low reactance, high resistance and low reactance High resistance and low reactance, low resistance and high reactance Low resistance and high reactance, high resistance and low reactance Low resistance and high reactance, low resistance and high reactance
Answer Explanation

MCQs 21: When the induction motor runs faster than the synchronous speed, the induction motor runs as

Asynchronous generator Induction generator Synchronous motor Such condition is not possible
Answer Explanation

MCQs 22: The induction generator is

Self exciting Separately exciting Both (a) and (b) None of these
Answer Explanation

MCQs 23: Which of the following is not true about induction generator?

Synchronization for induction generator is required Induction generators are more suitable for high speeds With the help of excitation supply and frequency, the voltage and frequency of induction motor are controlled The construction is rugged for rotating parts
Answer Explanation

MCQs 24: While drawing the graph of no load losses versus voltage, the voltage is extrapolated to V = 0. The extrapolated region shows

Copper losses Core losses Friction and windage losses None of these
Answer Explanation

MCQs 25: Applications of induction generators are

In railways for braking purpose Wind mils Drilling machines Only (a) and (b) None of these
Answer Explanation

MCQs 26: While using stator resistance starter with 3 phase induction motor, the resistances of the starter are kept at

Maximum Minimum Half of the maximum value None of these
Answer Explanation

MCQs 27: When stator resistance starter is used, the factor by which stator voltage reduces is say x. If x<1, then due to stator resistance starter, the starting torque

Increases by fraction x Reduces by fraction x ∧ 2 Reduces by fraction x Increases by fraction x ∧ 2
Answer Explanation

MCQs 28: An autotransformer starter is suitable for

Star connected induction motor Delta connected induction motor Both (a) & (b) None of these
Answer Explanation

MCQs 29: The cheapest starter for induction motor is

Stator resistance starter Autotransformer starter Star-delta starter Rotor resistance starter
Answer Explanation

MCQs 30: Windings of star-delta starter while starting and during running are connected in

Star, delta Delta, delta VStar, star Delta, star
Answer Explanation

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