Synchronous motors

[amp_mcq option1=”the supply voltage and the back e.m.f.” option2=”magnetising current and back e.m.f.” option3=”the rotating stator flux and rotor poles” option4=”none of the above” correct=”option3″]

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

[amp_mcq option1=”field current and armature current” option2=”terminal voltage and load factor” option3=”power factor and field current” option4=”armature current and power factor” correct=”option2″]

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

[amp_mcq option1=”direcly proportional to the synchronous reactance” option2=”inversely proportional to the synchronous reactance” option3=”equal to the synchronous reactance” option4=”none of the above” correct=”option2″]

Detailed SolutionSynchronsizingpower of a synchronous machine is

[amp_mcq option1=”has large values for low excitation i niy” option2=”has large values for high excitation only” option3=”has large values for low and high excitation” option4=”any of the above” correct=”option3″]

Detailed SolutionThe armature current of the synchronous motor

[amp_mcq option1=”speed” option2=”load” option3=”load angle” option4=”all of the above” correct=”option4″]

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

[amp_mcq option1=”zero or 0.8 leading” option2=”unity or 0.8 lagging” option3=”unity or 0.8 leading” option4=”unity or zero” correct=”option3″]

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

[amp_mcq option1=”alternator type machines” option2=”induction type machines” option3=”salient pole type machines” option4=”smooth cylindrical type machines” correct=”option1″]

Detailed SolutionMostly, synchronous motors are of

[amp_mcq option1=”static condenser” option2=”condenser” option3=”synchronous condenser” option4=”none of the above” correct=”option3″]

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

[amp_mcq option1=”Of reducing number of slip rings on the rotor” option2=”Armature is associated with large power as compared to the field circuits” option3=”Of difficulty of providing high voltage insulation on rotor” option4=”All of the above reasons” correct=”option4″]

Detailed SolutionArmature of a synchronous machine is

[amp_mcq option1=”Windage loss” option2=”Copper losses” option3=”Any of the above” option4=”None of the above” correct=”option1″]

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