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This section includes 13 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. |
Ideally the voltage regulation of an alternator should be ___________ |
A. | zero |
B. | infinite |
C. | 50% |
D. | 100% |
Answer» B. infinite | |
2. |
If the emf from the air gap line is the 3-phase alternator is 440V per phase and armature current is 110 A. The synchronous reactance is? |
A. | 4 ohms |
B. | 2 ohms |
C. | 6.92 ohms |
D. | 2.32 ohms |
Answer» B. 2 ohms | |
3. |
In a calculation, the actual voltage regulation is 33.1% while the calculated value of the voltage regulation is 32.9%. This infers that the chosen method has been ___________ |
A. | zpf or asa |
B. | emf |
C. | mmf |
D. | mmf or zpf |
Answer» B. emf | |
4. |
In a calculation, the actual voltage regulation is 33.1% while the calculated value of the voltage regulation is 25%. This infers that the chosen method has been ___________ |
A. | emf |
B. | mmf |
C. | asa |
D. | zpf |
Answer» C. asa | |
5. |
In a calculation, the actual voltage regulation is 33.1% while the calculated value of the voltage regulation is 56.8%. This infers that the chosen method has been ___________ |
A. | emf |
B. | mmf |
C. | asa |
D. | zpf |
Answer» B. mmf | |
6. |
The preferred order of calculating the voltage regulation is ___________ |
A. | ZPF > ASA > MMF > EMF |
B. | ZPF > MMF > ASA > EMF |
C. | ASA > MMF > ASA > EMF |
D. | EMF > ASA > ZPF > MMF |
Answer» B. ZPF > MMF > ASA > EMF | |
7. |
Mmf method of voltage regulation is called _______ while the emf method is __________ |
A. | optimistic, pessimistic |
B. | pessimistic, pessimistic |
C. | optimistic, optimistic |
D. | pessimistic, optimistic |
Answer» B. pessimistic, pessimistic | |
8. |
In mmf method ___________ |
A. | all the emf is scaled to mmf |
B. | only the mmf values are considered neglecting impedance drop |
C. | all the emf are taken zero |
D. | emf is converted to saturated impedance drops |
Answer» B. only the mmf values are considered neglecting impedance drop | |
9. |
Emf method is also known as ___________ |
A. | pessimistic method |
B. | optimistic method |
C. | zero power factor method |
D. | none of the mentioned |
Answer» B. optimistic method | |
10. |
The emf method of the voltage regulation is applicable only to cylindrical rotor alternator due to ___________ |
A. | resultant air gap flux is not affected by angular position of rotor |
B. | uniform angular position of rotor |
C. | non uniform angular position of rotor |
D. | saliency of the poles is a trouble while estimating the emf |
Answer» B. uniform angular position of rotor | |
11. |
Alternator on infinite bus bar has constant ___________ |
A. | terminal voltage and frequency |
B. | frequency |
C. | power factor |
D. | power factor and terminal voltage |
Answer» B. frequency | |
12. |
Voltage regulation for an alternator operating at leading power factor is negative due to ___________ |
A. | magnetizing nature of armature reaction |
B. | demagnetizing nature of armature reaction |
C. | cross-magnetizing nature of armature reaction |
D. | all of the mentioned |
Answer» B. demagnetizing nature of armature reaction | |
13. |
When the load on an alternator is varied, its terminal voltage also changes due to _____________ |
A. | armature resistance |
B. | leakage reactance |
C. | armature reaction |
D. | all of the mentioned |
Answer» B. leakage reactance | |