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 leading power factor with under-excitation no change of power factor lagging power factor with over-excitation leading power factor with over-excitation leading power factor with under-excitation no change of power factor lagging power factor with over-excitation ANSWER DOWNLOAD EXAMIANS APP
Synchronous Motors In a synchronous motor which loss varies with load ? Core loss Windage loss Bearing friction loss Copper loss Core loss Windage loss Bearing friction loss Copper loss ANSWER DOWNLOAD EXAMIANS APP
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 by shifting its phase backward causes motor to take more current The rotor strengthens the rotating field causing more motor current The increased load has to take more current The back e.m.f. decreases causing an increase in motor current The rotor by shifting its phase backward causes motor to take more current The rotor strengthens the rotating field causing more motor current ANSWER DOWNLOAD EXAMIANS APP
Synchronous Motors If one phase of a 3 phase synchronous motor is short circuited, motor Will refused ro start Will overheat in spots Will fail to pull into step Will not come upto speed Will refused ro start Will overheat in spots Will fail to pull into step Will not come upto speed ANSWER DOWNLOAD EXAMIANS APP
Synchronous Motors An important advantage of a synchronous motor over wound round induction motor is that its power factor may be varied at will its speed is independent of supply frequency its speed may be controlled more easily None of these its power factor may be varied at will its speed is independent of supply frequency its speed may be controlled more easily None of these ANSWER DOWNLOAD EXAMIANS APP
Synchronous Motors The percentage slip in case of a synchronous motor is zero 0.005 1 0.01 zero 0.005 1 0.01 ANSWER DOWNLOAD EXAMIANS APP
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