Synchronous motors

[amp_mcq option1=”remains constant at all loads” option2=”varies with speed” option3=”varies with the load” option4=”varies with power factor” correct=”option1″]

Detailed SolutionThe magnitude of field flux in a 3-phase synchronous motor

[amp_mcq option1=”stop” option2=”run as induction motor” option3=”function as static condenser” option4=”burn with dense smoke” correct=”option1″]

Detailed SolutionIf the field winding of an unloaded salient pole synchronous motor is open circuited, the motor will

[amp_mcq option1=”power factor as well as armature current will decrease” option2=”power factor as well as armature current will increase” option3=”power factor will increase but armature current will decrease” option4=”power factor will decrease and armature current will increase” correct=”option1″]

Detailed SolutionA synchronous motor is running on a load with normal excitation. Now if the load on the motor is increased

[amp_mcq option1=”back e.m.f.” option2=”armature current” option3=”power factor” option4=”torque angle” correct=”option1″]

Detailed SolutionA synchronous motor running with normal excitation adjusts to load increases essentially by increase in

[amp_mcq option1=”decreases with increase in its excitation” option2=”increases with increase in its excitation” option3=”remains unaffected with increase in excitation” option4=”any of the above” correct=”option2″]

Detailed SolutionStability of a synchronous machine

[amp_mcq option1=”decrease both armature current and power factor” option2=”decrease armature current but increase power factor” option3=”increase armature current but decrease power factor” option4=”increase both its armature current and power factor” correct=”option3″]

Detailed SolutionThe effect of increasing the load on a synchronous motor running with normal excitation is to

[amp_mcq option1=”vector sum of Eb and V” option2=”arithmetic sum of Eb and V” option3=”arithmetic difference of Eb and V” option4=”vector difference of Eh and V” correct=”option1″]

Detailed SolutionThe net armature voltage of a synchronous motor is equal to the

[amp_mcq option1=”d.c. excitation only” option2=”speed of the motor” option3=”load on the motor” option4=”both the speed and rotor flux” correct=”option4″]

Detailed SolutionIn a synchronous motor, the magnitude of stator back e.m.f. (Eb) depends on

[amp_mcq option1=”Applied voltage of the motor” option2=”Motor speed” option3=”excitation of a synchronous motor changes A. Applied voltage of the motor B. Motor speed C. Power factor of power drawn by the motor” option4=”Any of the above” correct=”option4″]

Detailed SolutionChange of D.C. excitation of a synchronous motor changes

[amp_mcq option1=”under-loaded” option2=”over-loaded” option3=”under-excited” option4=”over-excited” correct=”option4″]

Detailed SolutionA synchronous motor can be used as a synchronous capacitor when it is