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MCQs 1: The advantages of star-delta starter over other types of starter is

Cheapest of all Maintenance free Both (a) & (b) None of these
Answer Explanation

MCQs 2: When rotor resistance starter is used with induction motor then

Only starting current is limited Only starting torque is limited Both starting current and starting torque are limited Neither starting current nor starting torque is limited
Answer Explanation

MCQs 3: Direct online starter also called D.O.L. starter is used for motors having capacity

Less than 5 h.p. Less than 10 h.p. Greater than 10 h.p. For any capacity motor
Answer Explanation

MCQs 4: The NO contact and NC contact of D.O.L. starter is normally

Open, closed Closed, open Open, open Closed, closed
Answer Explanation

MCQs 5: A machine without commutator, providing an ac emf to the external circuit is called as

D.C. generator Alternator Synchronous motor Transformer
Answer Explanation

MCQs 6: Practically, most of the alternators prefer which type of construction?

Rotating field type Rotating armature type Both are equally important None of these
Answer Explanation

MCQs 7: In synchronous machine poles are made up of thick steel laminations. In salient pole type rotor

Poles are projected out from the surface of the rotor The unslotted portions of the cylinder itself acts as the poles Both (a) and (b) None of these
Answer Explanation

MCQs 8: Salient pole type rotors are generally used for the range of 125 rpm to 500 rpm. The limiting factor for the size of the rotor is the

Rotating field type construction Rotating armature type construction Centrifugal force acting on the rotating member All of these
Answer Explanation

MCQs 9: The prime movers used to drive projected pole type alternator is

Water turbines I.C. engines Both (a) and (b) None of these
Answer Explanation

MCQs 10: Separate damper winding is necessary in

Smooth cylindrical type rotor Salient pole type rotor Both (a) and (b) None of these
Answer Explanation

MCQs 11: Generally, in alternator divided winding rotor is preferred to a conventional winding rotor, because it gives

Better damping Less harmonics More efficiency None of these
Answer Explanation

MCQs 12: The air gap in a salient pole machine is

Maximum at the center of poles Least at the center of poles and increases while moving away from the center Maximum at the center and decreases while moving away from the center Equally distributed
Answer Explanation

MCQs 13: The diameter and axial length of rotors of smooth cylindrical type rotors are

Small diameter, small axial length Large diameter, large axial length Large diameter, small axial length Small diameter, large axial length
Answer Explanation

MCQs 14: Which type of rotor is generally used for high speed alternators or turbo alternators?

Salient pole type Projected pole type Smooth cylindrical type Both (a) & (b)
Answer Explanation

MCQs 15: The phasor addition of stator and rotor mmfs is possible in a smooth cylindrical synchronous generator because

Mmfs of stator and rotor are stationary with respect to each other Mmf of stator is stationary and that of rotor is rotating Mmf of stator is rotating and that of rotor is stationary None of these
Answer Explanation

MCQs 16: The prime movers which are used to drive non projected type rotors are

I.C. engines Electric motors Steam turbines Both (b) & (c)
Answer Explanation

MCQs 17: In the brushless excitation system of synchronous generator, the feedback of output voltage of alternator is taken and given to the

Rotating armature a.c. excitor Diode rectifier Main alternator field Magnetic amplifier
Answer Explanation

MCQs 18: When we plot the magnitude of the induced emf against the time, the nature of the induced emf will be

Sinusoidal Square Triangular Parabolic
Answer Explanation

MCQs 19: During the one complete revolution of the conductor in a 4 pole synchronous generator, induced emf will experience

Two times maxima and two times zero Two times maxima and four times zero Eight times maxima and eight times zero Four times maxima and four times zero
Answer Explanation

MCQs 20: In a synchronous generator, one pole is responsible for

90 degree electrical of induced emf 180 degree electrical of induced emf 360 degree electrical of induced emf 720 degree electrical of induced emf
Answer Explanation

MCQs 21: If the rotor poles of a 6 pole synchronous generator shift by 8 mechanical degrees from no load to full load, then its torque angle will be

12 degrees 24 degrees 48 degrees 136 degrees
Answer Explanation

MCQs 22: If coil side in one slot is connected to a coil side in another slot which is one pole pitch distance away from first slot, the winding is said to be

Short pitched Full pitched Concentrated Distributed
Answer Explanation

MCQs 23: Among the following sentences which is/are true about short pitch coils

Less amount of copper is required Eliminates high frequency harmonics Minimizes eddy current and hysteresis losses All of the above
Answer Explanation

MCQs 24: In practice, which combination of armature winding is preferred for the alternators?

Single layer, full pitched and concentrated type Single layer, short pitched and distributed type Double layer, full pitched and concentrated type Double layer, short pitched and distributed type
Answer Explanation

MCQs 25: Due to short pitching, the induced emf gets

Reduced Increased Remains same None of these
Answer Explanation

MCQs 26: In a 4 pole, 3 phase alternator, armature has 40 slots. It is using an armature winding which is short pitched by one slot. Its coil span factor is

0.9 0.9243 0.9476 0.9876
Answer Explanation

MCQs 27: The factor by which there is reduction in the emf due to distribution of coils is called distribution factor. It is given by

sin (β / 2m) / msin(β / 2) sin(β / m) / msin(mβ / 2) sin(m β/2) / msin(β / 2) msin(β / 2) / sin(m β / 2)
Answer Explanation

MCQs 28: For a short pitch and distributed winding, the value of coil span factor and distributed factor

Both are less than unity Less than unity, greater than unity Greater then unity, less than unity Both are greater than unity
Answer Explanation

MCQs 29: An armature of a three phase, 8 pole alternators has 120 slots. The distribution factor is equal to

0.897 0.946 0.957 1
Answer Explanation

MCQs 30: A 3 phase, 50 Hz, 8 pole, star connected alternator has 120 slots having 10 conductors per slot. The flux per pole is 0.02 Wb and distributed sinusoidally. The induced emf per phase for full pitch winding is

849.816 V 956.782 V 1046.812 V None of these
Answer Explanation

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