HomeElectrical machines best mcqSynchronous machines best question Synchronous machines best question Education March 31, 2023 0 1➤ Higher synchronous reactance is preferred in the present day alternator, beacuse one can have Reduce transient current Reduce harmonics current Higher voltage regulation with load All of these2➤ The short circuit characteristics of alternator isAlways linearNone of these Always non Linear Both a and c 3➤ The rating of synchronous machine is usually governed by its Temperature rise SpeedWeightNone of these4➤ How the reactive power delivered by a synchronous generator be controlled By changing the prime mover input By changing direction of rotation By changing the excitation By changing the prime mover speed5➤ A synchronous generator is feeding a zero power (lagging) load at rated current. The armature reaction isMagnetizingCross magnetizing Demagnetizing Both a and b6➤ When the load (inductive) is thrown off the terminal voltage will Remains constant Increase DecreaseNone of these7➤ The leakage reactance of three phase alternators is determined by performing Short circuit and slip testOpen and short circuit testOpen circuit and zero power factor test Zero power factor and slip test8➤ In an alternators short circuit current is limited by the Saturated synchronous impedance Unsaturated synchronous impedance Both a and bAll of these9➤ While starting a synchronous motor it's field winding should beShort circuitedKept open Connected to a DC source None of the above 10➤ The maximum power developed by a synchronous motor depends on Supply voltage Excitation current Both a and b None 11➤ A synchronous motor is cheaper than 3 phase induction motor for_________High speed high output Low speed High output High speed low outputAny of the abice12➤ When Synchronous motor is pulled out of synchronism the stator current ________Becomes 0Is Decrease too muchRemains unchanged Is increased too much 13➤ The mechanical power developed by synchronous motor is independent of________SpeedTorque angleField excitation Applied voltage14➤ Small synchronous motors are started byVariable frequency sourcePony motorsDamper windingNone15➤ Synchronous motor are generally used in application requiring Infrequent startingSudden application of heavy loadVariable speed Frequent stopping 16➤ The stator of modern alternators are wound for______phase groups 180°240°120°60°17➤ It is desirable to eliminate 5th harmonic voltages from the phase volatage of an alternators. The coil should be short pitched by an electrical angle of30 °72°36°18°18➤ In a synchronous Machine hunting is predominantly damped byCopper losses in rotorMechanical losses in the rotorCopper losses in the stator Iron lossess in rotor19➤ Modern alternators are designed to have poor regulations as itIncrease the value of short circuit current Limit the value of short circuit current Both a and bIncrease efficiency of operation 20➤ The synchrounous reactance is the Combine reactance due to leakage flux and armature reaction Reactance due to leakage fluxReaction due to armature reaction of machineBoth a and b21➤ In a synchronous generator delivering lagging power factor loadThe excitation emf leads terminal volatage by the power angle Excitation emf leads the terminal voltage by the power factor angle Both a and bThe excitation emf lags the terminal voltage by power angle22➤ For maximum current during slip test on a synchronous machine the armature mmf align along45°to q-axis45°to d-axisq-axisd-axis23➤ In which of the following is the reactance power developed Squirrel cage induction motor Transformer Salient pole alternator Cylindrical pole alternator24➤ In a 3-phase synchrounous motor the magnitude of field fluxRemains constant at all loadsVaries with loadVaries with power factor Varries with speed25➤ A 3 phase synchrounous motor needs dc supply for excitation At the starting instant onlyContinuouslyOf stator None of these SubmitYour score is Tags Electrical machines best mcq Newer Older