Voltage Regulation of an Alternator
Q1. The open circuit voltage and short circuit current of a 3 phase, star connected alternator are 1050 V and 250 A respectively. Its field current is 12 A. Then the synchronous impedance of alternator will bea. 1.34 ohm
b. 1.69 ohm
c. 2.42 ohm
d. 2.85 ohm
View Answer / Hide AnswerQ2. A 6 kVA, 220 v 3 phase, star connected synchronous generator has a winding resistance of 0.15 ohm per phase and synchronous reactance of 6.1 ohm per phase. The voltage regulation of alternator at a load power factor of 0.8 lagging will bea. 58.10 %
b. 68.43 %
c. 69.02 %
d. 72.81 %
View Answer / Hide AnswerQ3. If two mechanically coupled alternators deliver power at 50 Hz and 60 Hz respectively, then the highest speed of alternators will bea. 1200 rpm
b. 1500 rpm
c. 600 rpm
d. 300 rpm
View Answer / Hide AnswerQ4. If the armature resistance and synchronous reactance of a 2 MVA, 11 kV, 3 phase star connected alternator are 2 ohm and 20 ohm per phase respectively. The value of full load generated voltage per phase at unity power factor will bea. 6888.45 V
b. 6899.65 V
c. 6999.45 V
d. 7111.45 V
View Answer / Hide AnswerQ5. As the value of load power factor of an alternator changes, the value of armature reaction reactancea. Remains constant
b. Changes
View Answer / Hide AnswerQ6. The given figure shows the load characteristics of an alternator. Which among the following is correct?a. A – Leading p.f., B – unity p.f., C – lagging p.f.
b. A – Lagging p.f., B – unity p.f., C – leading p.f.
c. A – Leading p.f., B – lagging p.f., C – unity p.f.
d. A – Unity p.f., B – leading p.f., C – lagging p.f.
View Answer / Hide AnswerANSWER: a. A – Leading p.f., B – unity p.f., C – lagging p.f.
Q7. In an alternator, the voltage regulation will be positive when the power factor of the load isa. Leading
b. Unity
c. Lagging
d. Both ( b ) & ( c )
View Answer / Hide AnswerANSWER: d. Both ( b ) & ( c )
Q8. On unity power factor, the terminal voltage of an alternator isa. Always less than induced emf
b. Always greater than induced emf
c. Same as induced emf
d. None of these
View Answer / Hide AnswerANSWER: a. Always less than induced emf
Q9. The percentage voltage regulation of an alternator is given byA. {(E
ph - V
ph/ E
ph) *100}
B. {(V
ph - E
ph / E
ph)*100}
C. {(E
ph - V
ph / V
ph)*100}
D. {(V
ph - E
ph / V
ph)*100}
View Answer / Hide AnswerANSWER: C. {(Eph-Vph / V ph)*100}