1. In a synchronous motor
a) the rotor mmf and stator mmf are stationary with respect to each other
b) the speed of rotor mmf is slightly less than the speed of stator mmf
c) the speed of rotor mmf is slightly more than the speed of stator mmf
d) none of these
ans. a
2. In a 3-phase alternator the unsaturated synchronous reactance is 3 ohms per phase. The saturated synchronous reactance is
a) 3 ohms
b) more than 3 ohms
c) less than 3 ohms
d) none of these
ans. c
3. The short-circuit characteristic of an alternator is
a) always linear
b) always non-linear
c) sometimes linear and sometimes non-linear
d) none of these
ans. a
4. Under short circuit conditions, the power factor of an alternator is
a) almost zero lagging
b) unity
c) about 0.6 lagging
d) none of these
ans. a
5. High speed alternators usually have
a) salient pole rotors
b) cylindrical rotors
c) both a and b
d) none of these
ans. b
6. Cylindrical rotor alternators have
a) large length to diameter ratio
b) small length to diameter ratio
c) vertical configuration
d) none of these
ans. a
7. Salient pole machine have
a) large no of poles
b) small no of poles
c) small diameters
d) long cores
ans. a
8. To ensure proper cooling, cylindrical rotor alternators use
a) radial ducts only
b) axial ducts only
c) both radial and axial ducts only
d) none of these
ans. c
9. Modern alternators usually have short pitched winding
a) to improve the voltage wave shape
b) to improve the magnitude of the generated voltage
c) to increase the machine rating
d) none of these
ans. a
10. If the armature current is leading the generated voltage by 90 degrees the effect of armature reaction will be
a) demagnetizing
b) magnetizing
c) partly magnetizing and partly cross magnetizing
d) none of these
ans. b
a) the rotor mmf and stator mmf are stationary with respect to each other
b) the speed of rotor mmf is slightly less than the speed of stator mmf
c) the speed of rotor mmf is slightly more than the speed of stator mmf
d) none of these
ans. a
2. In a 3-phase alternator the unsaturated synchronous reactance is 3 ohms per phase. The saturated synchronous reactance is
a) 3 ohms
b) more than 3 ohms
c) less than 3 ohms
d) none of these
ans. c
3. The short-circuit characteristic of an alternator is
a) always linear
b) always non-linear
c) sometimes linear and sometimes non-linear
d) none of these
ans. a
4. Under short circuit conditions, the power factor of an alternator is
a) almost zero lagging
b) unity
c) about 0.6 lagging
d) none of these
ans. a
5. High speed alternators usually have
a) salient pole rotors
b) cylindrical rotors
c) both a and b
d) none of these
ans. b
6. Cylindrical rotor alternators have
a) large length to diameter ratio
b) small length to diameter ratio
c) vertical configuration
d) none of these
ans. a
7. Salient pole machine have
a) large no of poles
b) small no of poles
c) small diameters
d) long cores
ans. a
8. To ensure proper cooling, cylindrical rotor alternators use
a) radial ducts only
b) axial ducts only
c) both radial and axial ducts only
d) none of these
ans. c
9. Modern alternators usually have short pitched winding
a) to improve the voltage wave shape
b) to improve the magnitude of the generated voltage
c) to increase the machine rating
d) none of these
ans. a
10. If the armature current is leading the generated voltage by 90 degrees the effect of armature reaction will be
a) demagnetizing
b) magnetizing
c) partly magnetizing and partly cross magnetizing
d) none of these
ans. b
