vary with load ?
(A) Copper losses
of the above.
47. In a 3-phase. 400 V, 50 Hz salient pole
synchronous motor, the maximum power is obtained when the load angle is
(B) less than 90°
(D) more than 90°.
48. A high starting torque synchronous motor has
of the above.
49. In a three phase synchronous motor, the
magnitude of field flux
constant at all loads
with power factor.
50. The parameter connected with the operation
of a synchronous motor are
When the excitation
of the motor is varied, which parameters vary along with it
(A) I only
(B) II only
(C) II and III only
(D) I, II and III.
51. A 3 phase, 400 V, 50 Hz salient pole
synchronous motor is running on no load. If there is break in the excitation
winding of the motor
the motor will stop
winding will get overheated
motor will run as reluctance motor at the rated rpm
motor will run as reluctance motor at lower rpm.
52. In the figure shown with curve represents
the variation of synchronous reactance for a synchronous motor with field
(A) curve A
(B) curve B
(C) curve C
(D) curve D.
53. A synchronous motor is said to be ‘floating’ when it operates
no load and without losses
constantly varying load
high load and variable supply voltage.
54. The negative phase sequences in a three phase synchronous motor
is under loaded
voltage is supplied
armature is hot.
55. The field winding of a synchronous motor is
shorted. A variable voltage is now supplied to the stator. The result will be
stator winding will bum
motor will not run
will rotate at synchronous speed on light load
will rotate at a speed which is less than the synchronous speed.
56. In a three phase synchronous motor, the
along the resultant air-gap flux wave φ r
opposite to φ r
(C) lag φ r
(D) lead φ r
57. A 3 phase synchronous motor is running clockwise. In case the direction
of its field current is reversed
(A) the motor will continue to run in the same direction
(B) the motor will run in the reverse direction
(C) the motor will stop
60. In a synchronous motor, the synchronizing power comes into action
(A) rotor speed is equal to synchronous speed
(B) rotor speed is less than synchronous speed
(C) rotor speed is more than synchronous speed
(D) rotor speed is either less or more than synchronous speed.