Synchronous motors Archives

41. The magnitude of field flux in a 3-phase synchronous motor

remains constant at all loads

varies with speed

varies with the load

varies with power factor

Detailed SolutionThe magnitude of field flux in a 3-phase synchronous motor

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

Detailed SolutionIf the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will

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

Detailed SolutionA synchronous motor is running on a load with normal excitation. Now if the load on the motor is increased

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

Detailed SolutionA synchronous motor running with normal excitation adjusts to load increases essentially by increase in

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

Detailed SolutionStability of a synchronous machine

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

Detailed SolutionThe effect of increasing the load on a synchronous motor running with normal excitation is to

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

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

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

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

Detailed SolutionA synchronous motor can be used as a synchronous capacitor when it is

Page 1 Page 2 Page 3 Page 4 Page 5

Test 1 Test 2

Exit mobile version