Electrical Machines Questions and Answers – Power Angle Characteristics of Synchronous Machines

This set of Electrical Machines Multiple Choice Questions & Answers (MCQs) focuses on “Power Angle Characteristics of Synchronous Machines”.

1. Choose the correct power angle characteristics for the synchronous motor and generator.
a)
b)
c)
d) None of the mentioned
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2. For a 3 phase 400V alternator having 0.5pu of synchronous reactance and its excitation voltage of 1.2pu and Vt of 1pu. Then the power delivered to the infinite bus is?
a) 2.4pu
b) 4.8pu
c) 1.44pu
d) 1pu
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3. For a 3 phase 400V alternator supplying a load of 0.8 pf lagging at an armature current of 1.1pu. The power delivered to load is?
a) 0.88pu
b) 0.7pu
c) 0.66pu
d) 1.375pu
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4. The power-angle characteristic for a three phase salient pole alternator is most correctly shown by?
a)
b)
c)
d)
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5. A 3 phase 400V salient pole alternator is running at no-load. Suddenly the excitation is removed then the net power in the machine is proportional to _____________
a) sin 2d
b) sin d
c) cos 2d
d) 0
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6. A 3 phase 400V cylindrical rotor is running at 1500rpm. Suddenly the field excitation zero. Then the net reluctance power is?
a) 0
b) sin 2d
c) cos d
d) cos 2d
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7. A cylindrical rotor alternator can also run as reluctance motor.
a) True
b) False
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8. If the synchronous machine is connected to an infinite bus of constant voltage Vt, through a transformed, a transmission line of reactance ‘X’. Then power for a cylindrical machine is?
a) P = (Ef*Vt sinδ)/(Xs + X)
b) P = (Ef*Ef sin2δ)/(Xs + X)
c) P = (Ef*Vt sinδ)/(Xs – X)
d) P = (Vt*Vt sinδ)/(Xs + X)
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9. Maximum power in cylinder rotor alternator occurs at load angle of __________
a) 90 degree
b) 45 degree
c) less than 90 degree
d) 180 degree
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10. A synchronous generator is operating with a Ef=1.40pu. This machine having Xs of 1.2pu, is delivering a synchronous power of 0.5pu to the bus. If the prime-mover torque is increased by 1%, by how much will the synchronous power P change?
a) 1%
b) 10%
c) -1%
d) 4%
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11. A synchronous generator is running over excited with a Ef=1.40pu. This machine, with a synchronous reactance of 1.2pu, is delivering a synchronous power of 0.5pu to the bus. If the prime-mover torque is increased by 1%, by how much will the reactive power, Q change?
a) -0.475 %
b) 0.475%
c) 4.75%
d) -4.75%
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12. A synchronous machine which is synchronized with an infinite bus. If it is desired to obtain a condition when the machine delivers the real power to the IBB without changing the field excitation, then __________
a) reactive power will be consumed by the machine
b) reactive power will be delivered by the machine
c) no reactive power flow will take place
d) none of the mentioned
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13. The phasor addition of stator and rotor mmfs in a cylindrical rotor synchronous machine, is possible because __________
a) mmfs are rotating in opposite direction
b) mmfs are rotating in same direction at different speeds
c) mmfs are stationary with respect to each other
d) one mmf is stationary and the other mmf is rotating
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14. For the effective electromechanical energy conversion in the device, the developed torque depends upon __________
a) stator field and torque angle
b) stator field and rotor field
c) stator field and rotor field and the torque angle
d) stator field only
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15. In a synchronous machine, hunting is predominantly damped by __________
a) mechanical losses in the rotor
b) iron losses in rotor
c) copper losses of stator
d) copper losses of rotor
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Sanfoundry Global Education & Learning Series – Electrical Machines.

To practice all areas of Electrical Machines, here is complete set of 1000+ Multiple Choice Questions and Answers.