Synchronous motors

11. The torque angle, in a synchronous motor, is the angle between

the supply voltage and the back e.m.f.
magnetising current and back e.m.f.
the rotating stator flux and rotor poles
none of the above

Detailed SolutionThe torque angle, in a synchronous motor, is the angle between

12. For V-curves for a synchronous motor the graph is drawn between

field current and armature current
terminal voltage and load factor
power factor and field current
armature current and power factor

Detailed SolutionFor V-curves for a synchronous motor the graph is drawn between

13. Synchronsizingpower of a synchronous machine is

direcly proportional to the synchronous reactance
inversely proportional to the synchronous reactance
equal to the synchronous reactance
none of the above

Detailed SolutionSynchronsizingpower of a synchronous machine is

14. The armature current of the synchronous motor

has large values for low excitation i niy
has large values for high excitation only
has large values for low and high excitation
any of the above

Detailed SolutionThe armature current of the synchronous motor

15. The back e.m.f. of a synchronous motor depends on

speed
load
load angle
all of the above

Detailed SolutionThe back e.m.f. of a synchronous motor depends on

16. The standard full-load power factor ratings for synchronous motors are

zero or 0.8 leading
unity or 0.8 lagging
unity or 0.8 leading
unity or zero

Detailed SolutionThe standard full-load power factor ratings for synchronous motors are

17. Mostly, synchronous motors are of

alternator type machines
induction type machines
salient pole type machines
smooth cylindrical type machines

Detailed SolutionMostly, synchronous motors are of

18. A synchronous motor which works on a leading power factor and does not drive a mechanical load is called as

static condenser
condenser
synchronous condenser
none of the above

Detailed SolutionA synchronous motor which works on a leading power factor and does not drive a mechanical load is called as

19. Armature of a synchronous machine is

Of reducing number of slip rings on the rotor
Armature is associated with large power as compared to the field circuits
Of difficulty of providing high voltage insulation on rotor
All of the above reasons

Detailed SolutionArmature of a synchronous machine is

20. Which of the following losses, in a synchronous motor, does not vary with load?

Windage loss
Copper losses
Any of the above
None of the above

Detailed SolutionWhich of the following losses, in a synchronous motor, does not vary with load?

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