MCQOPTIONS
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MCQOPTIONS
This section includes 11 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. |
An 3 phase alternator star connected 400 V synchronous motor takes a power input of 5472 watts at rated voltage. Its synchronous reactance is 10** per phase and negligible resistance. If its excitation voltage is adjusted equal to the rated voltage of 400 V, its power factor is _______ |
| A. | cos(10 ) |
| B. | cos(20 ) |
| C. | cos(40 ) |
| D. | cos(30 ) |
| Answer» B. cos(20 ) | |
| 2. |
Under the conditions of maximum values of active or reactive power, a synchronous machine always absorbs reactive power. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 3. |
What is Synchronous motor? |
| A. | absorbs reactive power for maximum input real power |
| B. | absorbs reactive power for maximum input reactive power |
| C. | delivers reactive power for maximum input real power |
| D. | delivers reactive power for maximum input reactive power |
| Answer» B. absorbs reactive power for maximum input reactive power | |
| 4. |
If the synchronous motor connected to the infinite bus bar absorbs reactive power to it, then it must be operating at __________ |
| A. | leading pf |
| B. | lagging pf |
| C. | zero pf |
| D. | unity pf |
| Answer» C. zero pf | |
| 5. |
For an underexcited 3 phase synchronous motor, connected to IBB is __________ |
| A. | absorbing reactive power from IBB |
| B. | delivering reactive power to IBB |
| C. | absorbing zero reactive power from IBB |
| D. | delivering zero reactive power to IBB |
| Answer» B. delivering reactive power to IBB | |
| 6. |
If the synchronous motor connected to the infinite bus bar delivers positive reactive power to it, then it must be operating at __________ |
| A. | leading pf |
| B. | lagging pf |
| C. | zero pf |
| D. | unity pf |
| Answer» B. lagging pf | |
| 7. |
For an overexcited 3 phase synchronous motor, connected to infinite bus is __________ |
| A. | motor is delivering reactive power to IBB |
| B. | motor is absorbing reactive power to IBB |
| C. | motor is delivering zero reactive power to IBB |
| D. | none of the mentioned |
| Answer» B. motor is absorbing reactive power to IBB | |
| 8. |
Under the condition of maximum power delivered, reactive power is __________ |
| A. | negative |
| B. | positive |
| C. | zero |
| D. | same as previous condition |
| Answer» B. positive | |
| 9. |
Under the conditions of maximum reactive power output, the reactive power flowing out of an alternator is __________ |
| A. | positive |
| B. | negative |
| C. | zero |
| D. | equal to power |
| Answer» C. zero | |
| 10. |
When terminal voltage exceeds the excitation, then operating power factor is? |
| A. | leading |
| B. | lagging |
| C. | uPF |
| D. | zpf |
| Answer» B. lagging | |
| 11. |
When excitation given to a 3-phase alternator is equal to terminal voltage then ____________ |
| A. | the absorbed reactive power is zero |
| B. | the absorbed real power is zero |
| C. | the delivered real power is zero |
| D. | any of the mentioned |
| Answer» B. the absorbed real power is zero | |