A synchronous motor running with normal excitation adjusts to load increases essentially by increase in______________?
(A) back e.m.f.
(B) armature current
(C) power factor
(D) torque angle
The efficiency of a properly designed synchronous motor will usually fall in range___________?
(A) 60 to 70%
(B) 75 to 80%
(C) 85 to 95%
(D) 99 to 99.5%
Under which of the following conditions hunting of synchronous motor is likely to occur?
(A) Periodic variation of load
(B) Over-excitation
(C) Over-loading for long periods
(D) Small and constant load
A synchronous motor is running on a load with normal excitation. Now if the load on the motor is increased
(A) power factor as well as armature current will decrease
(B) power factor as well as armature current will increase
(C) power factor will increase but armature current will decrease
(D) power factor will decrease and armature current will increase
As the load is applied to a synchronous motor, the motor takes more armature current because
(A) the increased load has to take more current
(B) the rotor by shifting its phase backward causes motor to take more current
(C) the back e.m.f. decreases causing an increase in motor current
(D) the rotor strengthens the rotating field casuing more motor current
The power developed by a synchronous motor will be maximum when the load angle is____________?
(A) zero
(B) 45°
(C) 90°
(D) 120°
When the excitation of an unloaded salient pole synchronous motor suddenly gets disconnected______________?
(A) the motor stops
(B) it runs as a reluctance motor at the same speed
(C) it runs as a reluctance motor at a lower speed
(D) none of the above
A synchronous motor can be used as a synchronous capacitor when it is____________?
(A) under-loaded
(B) over-loaded
(C) under-excited
(D) over-excited
Mostly, synchronous motors are of_____________?
(A) alternator type machines
(B) induction type machines
(C) salient pole type machines
(D) smooth cylindrical type machines
The working of a synchronous motor is similar to_____________?
(A) gear train arrangement
(B) transmission of mechanical power by shaft
(C) distribution transformer
(D) turbine
(D) none of the above