MCQOPTIONS
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MCQOPTIONS
This section includes 13 Mcqs, each offering curated multiple-choice questions to sharpen your Dc Machines knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
A 440 V, 4-pole, 25 kW, dc generator has a wave-connected armature winding with 846 conductors. The mean flux density in the air-gap under the interpoles is 0.5 Wb/m2 on full load and the radial gap length is 0.3 cm. Number of turns required on each interpole is _________ |
| A. | 74 |
| B. | 84 |
| C. | 64 |
| D. | 54 |
| Answer» B. 84 | |
| 2. |
For a given 4-pole machine, carrying armature current 56.82 A, with 846 conductors. The mean flux density in the air gap under the interpoles is 0.5 Wb/m2 on full load and radial gap length is 0.3 cm. Ampere-turns required for an interpole is ____________ |
| A. | 3198 |
| B. | 2099 |
| C. | 4198 |
| D. | 6297 |
| Answer» D. 6297 | |
| 3. |
Formula for cancellation of reactance voltage on an average basis using interpoles ________ |
| A. | 2[Bi(av)liva] Nc = Lc (dic/dt) = Lc (2lc/tc) |
| B. | [Bi(av)liva] Nc = Lc (dic/dt) = Lc (2lc/tc)c) 2[Bi(av)liva] Nc = Lc (dic/dt) = Lc (lc/t |
| C. | [Bi(av)liva] Nc = Lc (dic/dt) = Lc (2lc/tc)c) 2[Bi(av)liva] Nc = Lc (dic/dt) = Lc (lc/tc) |
| D. | Cannot be determined |
| Answer» B. [Bi(av)liva] Nc = Lc (dic/dt) = Lc (2lc/tc)c) 2[Bi(av)liva] Nc = Lc (dic/dt) = Lc (lc/t | |
| 4. |
What is the size of interpolar air gap compare to main pole air gap? |
| A. | Small |
| B. | Same |
| C. | More |
| D. | Can be of any size |
| Answer» D. Can be of any size | |
| 5. |
Polarity of interpoles is one pole ahead in the direction of armature rotation in _____________ |
| A. | Motor |
| B. | Generator |
| C. | Always ahead |
| D. | Always behind |
| Answer» C. Always ahead | |
| 6. |
Interpoles are excited by keeping them in ____________ with armature. |
| A. | Series |
| B. | Parallel |
| C. | Anywhere |
| D. | Not kept with armature |
| Answer» B. Parallel | |
| 7. |
Interpoles are excited with ____________ |
| A. | Armature current |
| B. | Field current |
| C. | Separate supply |
| D. | Mains current |
| Answer» B. Field current | |
| 8. |
Which voltage is neutralized in voltage commutation process? |
| A. | Armature |
| B. | Reactance |
| C. | Field |
| D. | Cannot be determined |
| Answer» C. Field | |
| 9. |
What is the effect on time constant of transient current, as a result of resistance commutation? |
| A. | Remains same |
| B. | Decreases |
| C. | Increases |
| D. | Increases then decreases |
| Answer» E. | |
| 10. |
In resistance commutation method we add resistance between __________________ |
| A. | Brushes and external circuit |
| B. | Commutator and armature winding |
| C. | At field winding |
| D. | Commutator and brush |
| Answer» E. | |
| 11. |
Which are the methods for getting an ideal commutation? |
| A. | Resistance commutation |
| B. | Voltage commutation |
| C. | Current commutation |
| D. | Resistance and voltage commutation |
| Answer» E. | |
| 12. |
Why brushes shifting method is not employed in practical commutation? |
| A. | Expensive |
| B. | Construction problems |
| C. | Causes demagnetization |
| D. | Used practically |
| Answer» D. Used practically | |
| 13. |
Commutation is delayed due to __________ |
| A. | Leakage reactance |
| B. | Effect of armature reaction |
| C. | Leakage reactance and armature reaction |
| D. | Because of other factors |
| Answer» D. Because of other factors | |