Detailed SolutionThe magnitude of field flux in a 3-phase synchronous motor
Synchronous motors
remains constant at all loads
varies with speed
varies with the load
varies with power factor
Answer is Right!
Answer is Wrong!
42. If the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will
stop
run as induction motor
function as static condenser
burn with dense smoke
Answer is Right!
Answer is Wrong!
43. A synchronous motor is running on a load with normal excitation. Now if the load on the motor is increased
power factor as well as armature current will decrease
power factor as well as armature current will increase
power factor will increase but armature current will decrease
power factor will decrease and armature current will increase
Answer is Right!
Answer is Wrong!
44. A synchronous motor running with normal excitation adjusts to load increases essentially by increase in
back e.m.f.
armature current
power factor
torque angle
Answer is Right!
Answer is Wrong!
45. Stability of a synchronous machine
decreases with increase in its excitation
increases with increase in its excitation
remains unaffected with increase in excitation
any of the above
Answer is Right!
Answer is Wrong!
46. The effect of increasing the load on a synchronous motor running with normal excitation is to
decrease both armature current and power factor
decrease armature current but increase power factor
increase armature current but decrease power factor
increase both its armature current and power factor
Answer is Right!
Answer is Wrong!
47. The net armature voltage of a synchronous motor is equal to the
vector sum of Eb and V
arithmetic sum of Eb and V
arithmetic difference of Eb and V
vector difference of Eh and V
Answer is Right!
Answer is Wrong!
Detailed SolutionThe net armature voltage of a synchronous motor is equal to the
48. In a synchronous motor, the magnitude of stator back e.m.f. (Eb) depends on
d.c. excitation only
speed of the motor
load on the motor
both the speed and rotor flux
Answer is Right!
Answer is Wrong!
Detailed SolutionIn a synchronous motor, the magnitude of stator back e.m.f. (Eb) depends on
49. Change of D.C. excitation of a synchronous motor changes
Applied voltage of the motor
Motor speed
excitation of a synchronous motor changes A. Applied voltage of the motor B. Motor speed C. Power factor of power drawn by the motor
Any of the above
Answer is Right!
Answer is Wrong!
Detailed SolutionChange of D.C. excitation of a synchronous motor changes
50. A synchronous motor can be used as a synchronous capacitor when it is
under-loaded
over-loaded
under-excited
over-excited
Answer is Right!
Answer is Wrong!
Detailed SolutionA synchronous motor can be used as a synchronous capacitor when it is