### Synchronous Motors Objectives Part 04

61 . The size of synchronous motor decreases with the increase in flux density

62 . The flux density used in synchronous motor is around 0.5 to 0.6 wb/m2

63 . In a synchronous motor if the saturation is neglected, then the short circuit ration (SCR) will be related to synchronous reactance (xd) as SCR = 1 / xd

64 . In synchronous motor out of the following losses which one will have the highest proportion iron losses

65 . Which of the following losses is not dissipated by the stator core surface in a synchronous motor windage losses

66 . The speed of synchronous motor always remains constant

67 . Which of the following devices can be used as a phase advance synchronous motor working at leading power factor

68 . When synchronous motor is connected to infinite bus, while operating on leading power factor the excitation voltage will be more than the supply voltage

69 . In a synchronous motor total number of rotor slots is less than the total number of stator slots

70 . In a synchronous motor during hunting if the rotor speed becomes more than the synchronous speed dumpe bars develop induction generator torque

71 . If a synchronous motor fails to pull into synchronism after applying dc field current the probable cause may be low field current

72 . In case of 3 phase synchronous motor, maximum speed variation is zero

73 . The synchronous motors are not self-starting because the direction of instantaneous torque on the rotor reverse after half cycle

74 . In the above figure curve for leading power factors are on the right of line XY

75 . In the curves represent characteristics for 0, 10, 20 and 30 kW, not necessarily in that order, then curve for 0 kW is expected to be D

76 . The curve for 20 kW is expected to be A

77 . In a synchronous motor hunting can be minimised by using dampers, flywheel and by designing the motor for adequate synchronizing power

78 . A 3 phase 400 V, 50 Hz synchronous motor is working at 50 percent load. In case an increase in the field current of the motor causes a reduction in the armature current, it can be concluded that the motor is absorbing reactive power to the mains

79 . Inverted V-curves for a synchronous motor shows variation of power factor with dc field current when load on the motor remains constant.

80 . The armature current of the synchronous motor has large values for both low and high excitation