MCQOPTIONS
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MCQOPTIONS
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. |
Slip test is performed to obtain _____________ |
| A. | direct axis reactance and quadrature axis reactance |
| B. | slip |
| C. | positive and negative sequence reactance |
| D. | sub transient reactance |
| Answer» B. slip | |
| 2. |
When synchronous motor is running at synchronous speed, the damper winding produces? |
| A. | no torque |
| B. | eddy current torque |
| C. | damping torque |
| D. | torque aiding the developed torque |
| Answer» B. eddy current torque | |
| 3. |
A stationary alternator is connected to the infinite bus. It should not be connected because ____________ |
| A. | it will get short circuited |
| B. | it will operate as induction motor |
| C. | it will reduce bus bar voltage |
| D. | all of the mentioned |
| Answer» B. it will operate as induction motor | |
| 4. |
Consider a 3-phase alternator with negligible armature resistance and high rotational inertia delivering power to an isolated load when the armature terminals got short circuited. After sometime, the mechanical power input to the shaft of the machine is terminated at time t0. The short-circuit current circulating in the armature will change till the machine comes to halt at ts . Which one of the curves depicts this phenomena? |
| A. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-measurement-xd-xq-q14a.png"><img alt="3-phase alternator with armature resistance & high rotational inertia - option a" class="alignnone size-full wp-image-160968" height="243" sizes="(max-width: 300px) 100vw, 300px" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-measurement-xd-xq-q14a.png" srcset="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-measurement-xd-xq-q14a.png 300w, https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-measurement-xd-xq-q14a-100x80.png 100w" width="300"/></a> |
| B. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-measurement-xd-xq-q14b.png"><img alt="3-phase alternator with armature resistance & high rotational inertia - option b" class="alignnone size-full wp-image-160969" height="219" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-measurement-xd-xq-q14b.png" width="279"/></a> |
| C. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-measurement-xd-xq-q14c.png"><img alt="3-phase alternator with armature resistance & high rotational inertia - option c" class="alignnone size-full wp-image-160970" height="227" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-measurement-xd-xq-q14c.png" width="265"/></a> |
| D. | <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-measurement-xd-xq-q14d.png"><img alt="3-phase alternator with armature resistance & high rotational inertia - option d" class="alignnone size-full wp-image-160971" height="222" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-measurement-xd-xq-q14d.png" width="238"/></a> |
| Answer» B. <a href="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-measurement-xd-xq-q14b.png"><img alt="3-phase alternator with armature resistance & high rotational inertia - option b" class="alignnone size-full wp-image-160969" height="219" src="https://www.sanfoundry.com/wp-content/uploads/2017/05/electrical-machines-questions-answers-measurement-xd-xq-q14b.png" width="279"/></a> | |
| 5. |
In which one of the following is reluctance power developed? |
| A. | Salient pole alternator |
| B. | Non-salient pole alternator |
| C. | Squirrel cage rotor type induction motor |
| D. | All of the mentioned |
| Answer» B. Non-salient pole alternator | |
| 6. |
If the excitation of a 3-phase alternator operating on infinite bus bars is changed, which one of the following will get affected? |
| A. | Active real power of machine |
| B. | Reactive power of machine |
| C. | Terminal voltage of machine |
| D. | Frequency of machine |
| Answer» C. Terminal voltage of machine | |
| 7. |
An alternator with higher value of SCR has ____________ |
| A. | better voltage regulation and higher stability limit |
| B. | poor voltage regulation and lower stability limit |
| C. | poor voltage regulation and higher stability limit |
| D. | better voltage regulation and lower stability limit |
| Answer» B. poor voltage regulation and lower stability limit | |
| 8. |
When a 3 phase alternator is suddenly short circuited at its terminals, the initial value of the short circuit current is limited by which one of the following? |
| A. | x d |
| B. | x d |
| C. | xs |
| D. | Sum of x d, x d and xs |
| Answer» B. x d | |
| 9. |
If a cylindrical rotor synchronous generator, is connected to the IBB, if the field is made zero, then it behaves as ____________ |
| A. | induction generator for a short time |
| B. | induction motor |
| C. | synchronous motor |
| D. | synchronous generator |
| Answer» C. synchronous motor | |
| 10. |
A 3 Phase 400, 100 MVA alternator is connected to infinite bus bar. If the mechanical power input is more than the maximum reluctance power, the reluctance generator will lose synchronizm if ____________ |
| A. | field is open circuited |
| B. | field is short-circuited |
| C. | load is removed |
| D. | damper is removed |
| Answer» B. field is short-circuited | |
| 11. |
Slip test must be conducted at low armature terminal voltage. This is due to ____________ |
| A. | avoiding error due to large slip |
| B. | avoiding error due to small slip |
| C. | avoiding heating |
| D. | all of the mentioned |
| Answer» B. avoiding error due to small slip | |
| 12. |
The slip test is used to determine ____________ |
| A. | Xq |
| B. | Xd |
| C. | Xd and Xq |
| D. | None of the mentioned |
| Answer» B. Xd | |
| 13. |
The d-axis reactance is determined by ______________ |
| A. | OCC & SCC |
| B. | OCC |
| C. | Slip test |
| D. | SCC |
| Answer» B. OCC | |