41. A salient pole synchronous motor is running on no load. If its excitation is made off, it will
- continue running at synchronous speed
- continue running but at a speed slightly less than synchronous one
- stop
- none of these
42. What is the effect of the field failure of salient pole synchronous motor connected with infinite bus?
- Reduce motor torque and speed
- Not charge motor torque and speed
- Stop the motor
- Reduce motor torque but motor will continue to run at synchronous speed
43. The speed of a synchronous motor can be varied by varying its
- excitation supply
- voltage supply
- frequency
- load
44. A smooth cylindrical synchronous motor will always stop when
- excitation winding gets disconnected
- load varies
- supply voltage fluctuates
- supply frequency varies
45. A salient pole synchronous motor continues running even if its excitation current is reduced to zero. This is due to
- rotating magnetic field of stator
- rotating magnetic field of rotor
- magnetization of rotor salient poles by stator magnetic field
- interlocking action between stator and rotor rotating magnetic fields
46. When the excitation of normally operating unloaded salient-pole synchronous motor suddenly gets disconnected, it continues to run as a
- scharge motor
- spherical motor
- switched-reluctance motor
- variable-reluctance motor
47. For a 3-phase, 4 pole, 50 Hz synchronous motor, the frequency, pole number and the load torque are all halved. The motor speed will be
- 375 rpm
- 75 rpm
- 1500 rpm
- 3000 rpm
48. A synchronous motor with comparatively large air gap gives
- higher stability limit
- high synchronizing power making the machine less sensitive to load variations
- both (1) and (2)
- none of these
49. In a 3-phase synchronous motor, the magnitude of back emf set up in the stator depends on
- rotor excitation
- supply voltage
- rotor speed
- load on motor
50. The magnitude of counter or back emf in a synchronous motor
- is always less than supply voltage
- is always more than supply voltage
- is always equal to supply voltage
- may be either equal to or less than or more than supply voltage