MCQOPTIONS
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MCQOPTIONS
This section includes 15 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Machines knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
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 |
| Answer» E. | |
| 2. |
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 |
| Answer» D. stator field only | |
| 3. |
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 |
| Answer» D. one mmf is stationary and the other mmf is rotating | |
| 4. |
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 |
| Answer» B. reactive power will be delivered by the machine | |
| 5. |
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% |
| Answer» B. 0.475% | |
| 6. |
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% |
| Answer» B. 10% | |
| 7. |
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 |
| Answer» B. 45 degree | |
| 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 sin )/(Xs + X) |
| B. | P = (Ef*Ef sin2 )/(Xs + X) |
| C. | P = (Ef*Vt sin )/(Xs X) |
| D. | P = (Vt*Vt sin )/(Xs + X) |
| Answer» B. P = (Ef*Ef sin2 )/(Xs + X) | |
| 9. |
A cylindrical rotor alternator can also run as reluctance motor. |
| A. | True |
| B. | False |
| Answer» C. | |
| 10. |
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 |
| Answer» B. sin 2d | |
| 11. |
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 |
| Answer» B. sin d | |
| 12. |
The power-angle characteristic for a three phase salient pole alternator is most correctly shown by? |
| A. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-power-angle-characteristics-synchronous-machines-q4a.png"><img alt="The power-angle characteristic for a three phase salient pole alternator - option a" class="alignnone size-full wp-image-160949" height="222" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-power-angle-characteristics-synchronous-machines-q4a.png" width="300"/></a> |
| B. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-power-angle-characteristics-synchronous-machines-q4b.png"><img alt="The power-angle characteristic for a three phase salient pole alternator - option b" class="alignnone size-full wp-image-160950" height="209" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-power-angle-characteristics-synchronous-machines-q4b.png" width="300"/></a> |
| C. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-power-angle-characteristics-synchronous-machines-q4c.png"><img alt="The power-angle characteristic for a three phase salient pole alternator - option c" class="alignnone size-full wp-image-160951" height="193" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-power-angle-characteristics-synchronous-machines-q4c.png" width="300"/></a> |
| D. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-power-angle-characteristics-synchronous-machines-q4d.png"><img alt="The power-angle characteristic for a three phase salient pole alternator - option d" class="alignnone size-full wp-image-160952" height="179" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-power-angle-characteristics-synchronous-machines-q4d.png" width="300"/></a> |
| Answer» B. <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-power-angle-characteristics-synchronous-machines-q4b.png"><img alt="The power-angle characteristic for a three phase salient pole alternator - option b" class="alignnone size-full wp-image-160950" height="209" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-power-angle-characteristics-synchronous-machines-q4b.png" width="300"/></a> | |
| 13. |
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. | 0.8pu |
| C. | 0.66pu |
| D. | 1.375pu |
| Answer» D. 1.375pu | |
| 14. |
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 |
| Answer» B. 4.8pu | |
| 15. |
Choose the correct power angle characteristics for the synchronous motor and generator. |
| A. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-power-angle-characteristics-synchronous-machines-q1a.png"><img alt="The power angle characteristics for the synchronous motor & generator - option a" class="alignnone size-full wp-image-160946" height="179" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-power-angle-characteristics-synchronous-machines-q1a.png" width="300"/></a> |
| B. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-power-angle-characteristics-synchronous-machines-q1b.png"><img alt="The power angle characteristics for the synchronous motor & generator - option b" class="alignnone size-full wp-image-160947" height="185" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-power-angle-characteristics-synchronous-machines-q1b.png" width="300"/></a> |
| C. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-power-angle-characteristics-synchronous-machines-q1c.png"><img alt="The power angle characteristics for the synchronous motor & generator - option c" class="alignnone size-full wp-image-160948" height="193" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-power-angle-characteristics-synchronous-machines-q1c.png" width="300"/></a> |
| D. | None of the mentioned |
| Answer» B. <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-power-angle-characteristics-synchronous-machines-q1b.png"><img alt="The power angle characteristics for the synchronous motor & generator - option b" class="alignnone size-full wp-image-160947" height="185" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-power-angle-characteristics-synchronous-machines-q1b.png" width="300"/></a> | |