# Electrical Machine 12

Electrical Engineering MCQ Question Papers: Campus Placement

Subject: Electrical Machine 12

Part 6: List for questions and answers of Electrical Machine II

Q1.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 ?

a) 0.9

b) 0.9243

c) 0.9476

d) 0.9876

Q2.Due to short pitching, the induced emf gets ?

a) Reduced

b) Increased

c) Remains same

d) None of these

Q3.In practice, which combination of armature winding is preferred for the alternators??

a) Single layer, full pitched and concentrated type

b) Single layer, short pitched and distributed type

c) Double layer, full pitched and concentrated type

d) Double layer, short pitched and distributed type

Q4.Among the following sentences which is/are true about short pitch coils?

a) Less amount of copper is required

b) Eliminates high frequency harmonics

c) Minimizes eddy current and hysteresis losses

d) All of the above

Q5.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 ?

a) Short pitched

b) Full pitched

c) Concentrated

d) Distributed

Q6.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 ?

a) 12 degrees

b) 24 degrees

c) 48 degrees

d) 136 degrees

Q7.In a synchronous generator, one pole is responsible for?

a) 90 degree electrical of induced emf

b) 180 degree electrical of induced emf

c) 360 degree electrical of induced emf

d) 720 degree electrical of induced emf

Q8.During the one complete revolution of the conductor in a 4 pole synchronous generator, induced emf will experience?

a) Two times maxima and two times zero

b) Two times maxima and four times zero

c) Eight times maxima and eight times zero

d) Four times maxima and four times zero

Q9.When we plot the magnitude of the induced emf against the time, the nature of the induced emf will be ?

a) Sinusoidal

b) Square

c) Triangular

d) Parabolic

Q10.In the brushless excitation system of synchronous generator, the feedback of output voltage of alternator is taken and given to the ?

a) Rotating armature a.c. excitor

b) Diode rectifier

c) Main alternator field

d) Magnetic amplifier

Q11.The prime movers which are used to drive non projected type rotors are?

a) I.C. engines

b) Electric motors

c) Steam turbines

d) Both (b) and (c)

Q12.The phasor addition of stator and rotor mmfs is possible in a smooth cylindrical synchronous generator because?

a) Mmfs of stator and rotor are stationary with respect to each other

b) Mmf of stator is stationary and that of rotor is rotating

c) Mmf of stator is rotating and that of rotor is stationary

d) None of these

Q13.Which type of rotor is generally used for high speed alternators or turbo alternators? ?

a) Salient pole type

b) Projected pole type

c) Smooth cylindrical type

d) Both (a) and (b)

Q14.The diameter and axial length of rotors of smooth cylindrical type rotors are ?

a) Small diameter, small axial length

b) Large diameter, large axial length

c) Large diameter, small axial length

d) Small diameter, large axial length

Q15.The air gap in a salient pole machine is ?

a) Maximum at the center of poles

b) Least at the center of poles and increases while moving away from the center

c) Maximum at the center and decreases while moving away from the center

d) Equally distributed

Q16.Generally, in alternator divided winding rotor is preferred to a conventional winding rotor, because it gives?

a) Better damping

b) Less harmonics

c) More efficiency

d) None of these

Q17.Separate damper winding is necessary in ?

a) Smooth cylindrical type rotor

b) Salient pole type rotor

c) Both (a) and (b)

d) None of these

Q18.The prime movers used to drive projected pole type alternator is?

a) Water turbines

b) I.C. engines

c) Both (a) and (b)

d) None of these

Q19.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 ?

a) Rotating field type construction

b) Rotating armature type construction

c) Centrifugal force acting on the rotating member

d) All of these

Q20.In synchronous machine poles are made up of thick steel laminations. In salient pole type rotor ?

a) Poles are projected out from the surface of the rotor

b) The unslotted portions of the cylinder itself acts as the poles

c) Both (a) and (b)

d) None of these

Part 6: List for questions and answers of Electrical Machine II