# Electrical Machine 10

Electrical Engineering MCQ Question Papers: Campus Placement

Subject: Electrical Machine 10

Part 4: List for questions and answers of Electrical Machine II

Q1. If the load on a synchronous motor increases then its ?

a) Current drawn by motor increases and load angle decreases

b) Current drawn by motor decreases and load angle remains constant

c) Current drawn by motor remains constant and load angle increases

d) Current drawn by motor increases and load angle also increases

Q2.Back emf in case of synchronous motor depends on the ?

a) Excitation given to the field winding

b) Speed

c) Both (a) and (b)

d) None of the above

Q3. With increase in load, the speed of synchronous motor ?

a) Increases

b) Decreases

c) Remains constant

d) None of the above

Q4.A synchronous motor is started by using damper winding. When the motor runs at synchronous speed then the induced emf in the damper winding will be ?

a) Zero

b) Maximum

c) Half of the terminal voltage

d) None of these

Q5.The method used for starting synchronous motor is/are ?

a) Using pony motors

b) Using damper windings

c) As a slip ring induction motor

d) All of the above

Q6.Synchronous motors are ?

a) Self starting

b) Not self starting

c) Both (a) and (b)

d) None of these

Q7.Synchronous motor works on the principle of ?

a) Mutual induction

b) Electromagnetic induction

c) Magnetic locking

d) None of these

Q8.A synchronous motor draws 2 MVA at a power factor of 0.8 leading. If the efficiency developed in the motor is 90% then the power developed is equal to ?

a) 1212 kW

b) 1440 kW

c) 1676 kW

d) 1767 kW

Q9.For a two pole, 50 Hz, 3 phase synchronous motor the speed of rotating magnetic field is ?

a) 1000 rpm

b) 2000 rpm

c) 3000 rpm

d) 3500 rpm

Q10. a half cycle of fluxes in a synchronous motor, the resultant flux has rotated through ?

a) 0 degree

b) 90 degree

c) 180 degree

d) 360 degree

Q11. The meter of a vibrating reed frequency meter depends for its indications on the

a) Electrical resonance of thin flat steel reeds

b) Mechanical resonance of thin flat steel reeds

c) Mechanical resonance of thick flat steel reeds

d) Electrical resonance of thick flat steel reeds

Q12.When an alternator is connected to infinite bus bar, change in excitation for alternator will ?

a) Change the terminal voltage and power factor both

b) Affect only terminal voltage and power factor remains unaffected

c) Affect only power factor and terminal voltage remains unaffected

d) Neither terminal voltage will get affected nor power factor

Q13.The increase in mechanical torque in case of alternator will ?

a) Increase the armature current and reduce the power factor

b) Increase the armature current and improve the power factor

c) Decrease the armature current and improve the power factor

d) Decrease the armature current and reduce the power factor

Q14.In case of hydro generators, the driving torque can be changed by controlling the?

a) Gate opening

b) Throttle opening

c) Both (a) and (b)

d) None of these

Q15.If a 3 phase alternator is short circuited at its terminal, then the initial value of short circuit current will be limited by ?

a) Synchronous reactance

b) Transient reactance

c) Sub transient reactance

d) All of the above

Q16.In case of salient pole alternators, maximum output power can be obtained when power angle (d) is ?

a) Less than 90 degree

b) Equal to 90 degree

c) Greater than 90 degree

d) None of the above

Q17.The method used to determine Xd and Xq, the direct and quadrature axis reactance is called ?

a) Reactance test

b) Blondel’s two reaction theory

c) Slip test

d) All of the above

Q18.Depending upon the reluctances offered along the direct axis and quadrature axis, the armature reaction flux will ?

b) Lags behind the armature current

c) In phase with the armature current

d) None of these

Q19.The reluctance offered to the mmf wave is lowest when ?

a) It is aligned with the field pole axis

b) It is oriented at 90 degree to the field pole axis

c) Both (a) and (b)

d) None of these

Q20.According to Blondel’s two reaction theory, the armature mmf component acting along direct axis can be?

a) Demagnetizing

b) Magnetizing

c) Cross magnetizing

d) Either (a) or (b)

Part 4: List for questions and answers of Electrical Machine II