MCQOPTIONS
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MCQOPTIONS
This section includes 30 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. |
While conducting measurement for Xd and Xq, the information obtained is below. Which one of the following is correct? |
| A. | Xd = 3, Xq = 2.5 |
| B. | Xd = 6, Xq = 3.86 |
| C. | Xd = 3, Xq = 3.86 |
| D. | Xd = 6, Xq = 2.5View Answer |
| Answer» E. | |
| 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. |
The phasor diagram of a synchronous machine connected to an infinite bus is shown in the figure. The machine is acting as |
| A. | generator and operating at leading pf |
| B. | generator and operating at lagging pf |
| C. | motor and operating at leading pf |
| D. | motor and operating at lagging pf |
| Answer» B. generator and operating at lagging pf | |
| 8. |
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 | |
| 9. |
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 | |
| 10. |
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 | |
| 11. |
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 | |
| 12. |
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 | |
| 13. |
During slip test it would be observed that ____________ |
| A. | i is true, ii is false |
| B. | i is false, ii is true |
| C. | both true |
| D. | both falseView Answer |
| Answer» B. i is false, ii is true | |
| 14. |
The slip test is used to determine ____________ |
| A. | Xq |
| B. | Xd |
| C. | Xd and Xq |
| D. | None of the mentioned |
| Answer» B. Xd | |
| 15. |
The d-axis reactance is determined by ______________ |
| A. | OCC & SCC |
| B. | OCC |
| C. | Slip test |
| D. | SCC |
| Answer» B. OCC | |
| 16. |
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 | |
| 17. |
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 | |
| 18. |
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 | |
| 19. |
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 | |
| 20. |
Which of the options given will have no effect on the working of the synchronous motor if ignored? |
| A. | It has comparable reactance |
| B. | It requires dc excitation |
| C. | It can not be started under no load |
| D. | It has tendency to hunt |
| Answer» B. It requires dc excitation | |
| 21. |
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 | |
| 22. |
A synchronous motor is operated at a bus voltage of 1.5 pu and drawing 1.0 pu at zpf leading current. Its synchronous reactance is 0.4 pu. What is the excitation emf of the motor? |
| A. | 2.0 pu |
| B. | 1.5 pu |
| C. | 1.0 pu |
| D. | 1.1 pu |
| Answer» E. | |
| 23. |
An alternator with higher value of SCR ha? |
| 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 | |
| 24. |
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‚Äö√Ñ√∂‚àö√ë‚àö¬•d | |
| 25. |
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 | |
| 26. |
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 | |
| 27. |
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 | |
| 28. |
During slip test it would be observed that |
| A. | Swing of ammeter is wide |
| B. | Swing of voltmeter is wide |
| C. | i is true, ii is false |
| D. | i is false, ii is true |
| Answer» B. Swing of voltmeter is wide | |
| 29. |
The slip test is used to determine |
| A. | Xq |
| B. | Xd |
| C. | Xd and Xq |
| D. | None of the mentioned |
| Answer» B. Xd | |
| 30. |
The d-axis reactance is determined by |
| A. | OCC & SCC |
| B. | OCC |
| C. | Slip test |
| D. | SCC |
| Answer» B. OCC | |