Synchronous motors

[amp_mcq option1=”high excitation only” option2=”low excitation only” option3=”both high and low excitation” option4=”none of the above” correct=”option1″]

Detailed SolutionIn a synchronous motor, the armature current has large values for

[amp_mcq option1=”When supply voltage fluctuates” option2=”When load varies” option3=”When power factor is unity” option4=”Motor is under loaded” correct=”option1″]

Detailed SolutionRiunting in a synchronous motor takes place

[amp_mcq option1=”Windage loss” option2=”Bearing friction loss” option3=”Copper loss” option4=”Core loss” correct=”option3″]

Detailed SolutionIn a synchronous motor which loss varies with load ?

[amp_mcq option1=”d.c. shunt machines” option2=”d.c. series machines” option3=”d.c. compound machines” option4=”any of the above” correct=”option4″]

Detailed SolutionExciters of synchronous machines are

[amp_mcq option1=”lagging power factor only” option2=”leading power factor only” option3=”unity power factor only” option4=”lagging, leading and unity power factors” correct=”option4″]

Detailed SolutionA synchronous motor can operate at

[amp_mcq option1=”mild steel” option2=”chrome steel” option3=”alnico” option4=”stainless steel” correct=”option4″]

Detailed SolutionThe shaft of synchronous motor is made of

[amp_mcq option1=”Phase to phase winding resistance” option2=”Stator winding to earthed frame” option3=”Rotor winding to earthed shaft” option4=”All of the above” correct=”option4″]

Detailed SolutionWhich of the following resistances can be measured by conducting insulation resistance test on a synchronous motor ?

[amp_mcq option1=”Fluctuating loads” option2=”Variable speed loads” option3=”Low torque loads” option4=”Power factor corrections” correct=”option4″]

Detailed SolutionAn over excited synchronous motor is used for

[amp_mcq option1=”changing the load” option2=”changing the supply voltage” option3=”changing frequency” option4=”using brakes” correct=”option3″]

Detailed SolutionThe operating speed of a synchronous motor can be changed to new fixed value by

[amp_mcq option1=”its power factor may be varied at will” option2=”its speed is independent of supply frequency” option3=”its speed may be controlled more easily” option4=”none of the above” correct=”option2″]

Detailed SolutionAn important advantage of a synchronous motor over wound round induction motor is that