Synchronous Motors
Which of the following motors is non self starting?

Dc series motor
Wound rotor induction motor
Squirrel cage induction motor
Synchronous motor

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Synchronous Motors
A synchronous motor connected to infinite bus-bars has at constant full load, 100% excitation and unity power factor. On changing the excitation only, the armature current will have

leading power factor with over-excitation
no change of power factor
leading power factor with under-excitation
lagging power factor with over-excitation

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Synchronous Motors
As the load is applied to a synchronous motor, the motor takes more armature current because

The increased load has to take more current
The back e.m.f. decreases causing an increase in motor current
The rotor strengthens the rotating field causing more motor current
The rotor by shifting its phase backward causes motor to take more current

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