ELECTRICAL MACHINE MCQ_43_5( SYNCHRONOUS GENERATOR)


Q.61 When the generator supplies a load at unity power factor the armature reaction is
    A. demagnetizing
    B. cross magnetizing
    C. magnetizing
    D. partly magnetizing and party demagnetizing
Ans.: B

Q.62 When the generators supplies a load at leading power factor the armature reaction is
    A. partly magnetizing and partly cross magnetizing
    B. partly magnetizing and party demagnetizing
    C. partly demagnetizing and partly cross magnetizing
    D. magnetizing
Ans.: A

Q.63 The armature reaction at leading power factor the voltage induced in each phase by the armature reaction
    A. lead the respective phase current by 90°
    B. lag the respective phase current by 90°
    C. lead the respective phase current by 45°
    D. out of phase the respective phase current
Ans.: B

Q.64 The armature reaction is partly demagnetizing and partly cross magnetizing when the generator supplies a load at
    A. leading power factor
    B. unity power factor
    C. lagging power factor
    D. leading and lagging
Ans.: C

Q.65 The armature reaction at lagging power factor
    A. the armature reaction flux is opposite to the main field flux
    B. it will oppose and weaken the main field
    C. it said to be demagnetizing
    D. all of the above
Ans.: D

Q.66 Armature reaction at leading power factor
    A. the armature reaction flux is in the direction of main field flux
    B. it will aid the main field flux
    C. it is a magnetizing flux
    D. all of the above
Ans.: D

Q.67 The synchronous machine is operating in motoring mode
    A. the armature reaction mmf and flux are in out of phase
    B. the armature reaction mmf and flux are in phase opposition
    C. nature of armature reaction is reverse that of synchronous generator
    D. Both B and D
Ans.: D

Q.68 When motoring machine draws a lagging power factor current the armature reaction is
    A. magnetizing
    B. partly magnetizing and partly cross magnetizing
    C. cross magnetizing
    D. partly demagnetizing and partly cross magnetizing
Ans.: B

Q.69 The armature reaction is partly demagnetizing and partly cross magnetizing when the motor draws
    A. unity power factor current
    B. lagging power factor current
    C. leading power factor current
    D. at unity and leading
Ans.: C

Q.70 The actual voltage generated is the summation of
    A. voltage generated due to field excitation and armature reaction voltage
    B. voltage generated due to field excitation and terminal voltage
    C. terminal voltage and armature reaction voltage
    D. only the field excitation voltage
Ans.: A

Q.71 The armature reaction voltage can be modeled as an _______ with the internal generated voltage.
    A. resistor in series
    B. inductor in series
    C. capacitor in series
    D. series combination of inductor and resistor
Ans.: B

Q.72 The armature reaction and the leakage flux effects in the machine are represented by___
    A. capacitive reactance
    B. resistive
    C. inductive reactance
    D. inductive and capacitive reactance
Ans.: C

Q.73 The combine effect leakage flux and armature reaction is known as
    A. synchronous impedance
    B. synchronous reactance
    C. synchronous admittance
    D. none of the above
Ans.: B

Q.74 The synchronous impedance is give by
    A. Zs = Ra + jXs
    B. Zs = Ra – jXs
    C. Zs = Ra + jXa
    D. Zs = Ra + Xar
Ans.: A

Q.75 The power or torque angle is
    A. angle between Ea and V
    B. it varies with the load
    C. is a measure of air gap power developed in the machine
    D. all of the above
Ans.: D

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