21. The magnitude of emf induced in the armature of a synchronous motor depends upon
- supply voltage
- rotor excitation
- rotor speed
- flux density
22. In a synchronous motor, electromagnetic power varies
- directly as applied voltage
- directly as square of the applied voltage
- inversely as applied voltage
- none of the above
23. Electromagnetic torque present in rotating machines when
- stator winding carries current
- rotor winding carries current
- both stator and rotor windings carry current
- none of the above
24. The phase of emf induced in the armature of a synchronous motor depends upon
- rotor speed
- load
- both load and speed
- none of the above
25. In a synchronous motor, the synchronizing power comes into action when
- rotor speed either exceeds or falls below the synchronous speed
- rotor speed is equal to synchronous speed
- rotor speed falls below the synchronous speed
- rotor speed exceeds the synchronous speed
26. Synchronizing power of a synchronous motor varies
- directly as synchronous reactance
- directly as the square of the synchronous reactance
- inversely as the synchronous reactance
- none of the above
27. The total steady state torque to drive the synchronous motor and the load at synchronous speed is known as ______ torque.
- reluctance
- pull-out
- synchronous
- average
28. The coupling angle or load angle of a synchronous motor is defined as the space angle between the
- rotor and the stator poles of the same polarity
- rotor and the stator poles of opposite polarity
- rotor and stator teeth
- none of the above
29. The torque angle δ is defined as the space angle between
- stator field axis and resultant field axis.
- rotor field axis and resultant field axis.
- stator field axis and rotor field axis.
- stator field axis and mutual field axis.
30. The value of load angle for a synchronous motor depends mainly upon its
- excitation
- load
- speed
- supply voltage