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. |
The self and mutual inductances of a doubly excited magnetic system are Ls=0.6+0.20cos2 r H and Lr=0.75+0.30cos2 r H and Msr=0.8cos r H. For a stationary rotor at an angular position of r=60 ,what is the magnitude of torque when the currents is=20A DC and ir=10A DC? |
| A. | -233.88N-m |
| B. | +233.88N-m |
| C. | -467.76N-m |
| D. | +467.76N-m |
| Answer» B. +233.88N-m | |
| 2. |
An electromechanical energy conversion device has cylindrical stator but salient pole rotor. Rotor is not excited. If is the angle between stator field and rotor long axis, then average torque developed is proportional to (A and B are constants). |
| A. | Asin |
| B. | Asin2 |
| C. | Asin + Bsin2 |
| D. | zero |
| Answer» C. Asin + Bsin2 | |
| 3. |
An electromechanical energy conversion device has cylindrical stator but salient pole rotor. If is the angle between stator field and rotor field, the average torque developed is proportional to (A and B are constants) __________ |
| A. | Asin |
| B. | Asin2 |
| C. | Asin +Bsin2 |
| D. | |
| Answer» D. | |
| 4. |
Which component of torque equation, Te(av) = 1/8 Im2(Ld-Lq)sin2 +1/2 IfImMmaxsin represents the electromagnetic/interaction torque in single phase salient pole synchronous machine? |
| A. | 1/2 I<sub>f</sub>I<sub>m</sub>M<sub>max</sub>sin |
| B. | 1/8 I<sub>m</sub><sup>2</sup>(L<sub>d</sub>-L<sub>q</sub>)sin2 |
| C. | 1/8 I<sub>m</sub><sup>2</sup>(L<sub>d</sub>-L<sub>q</sub>)sin2 + 1/2 I<sub>f</sub>I<sub>m</sub>M<sub>max</sub>sin |
| D. | none of the mentioned |
| Answer» B. 1/8 I<sub>m</sub><sup>2</sup>(L<sub>d</sub>-L<sub>q</sub>)sin2 | |
| 5. |
Which of the following equation represents the reluctance torque of a salient pole synchronous machine? |
| A. | T<sub>e(av)</sub> = 1/4 I<sub>m</sub><sup>2</sup>(L<sub>d</sub>-L<sub>q</sub>)sin2 |
| B. | T<sub>e(av)</sub> = 2 I<sub>m</sub><sup>2</sup>(L<sub>d</sub>-L<sub>q</sub>)sin cos |
| C. | T<sub>e(av)</sub> = 1/8 I<sub>m</sub><sup>2</sup>(L<sub>d</sub>-L<sub>q</sub>) |
| D. | T<sub>e(av)</sub> = 1/8 I<sub>m</sub><sup>2</sup>(L<sub>d</sub>-L<sub>q</sub>)sin2 |
| Answer» E. | |
| 6. |
In a two phase cylindrical rotor synchronous machine, torque Te is _____________ |
| A. | constant at some instant of time |
| B. | changing at every instant of time |
| C. | constant at every instant of time |
| D. | changing at some instant of time |
| Answer» D. changing at some instant of time | |
| 7. |
In a two phase cylindrical rotor synchronous machine, the mutual inductance M between phase and phase winding is __________ |
| A. | M<sub>max</sub> |
| B. | 0 |
| C. | M<sub>min</sub> |
| D. | any of the mentioned |
| Answer» C. M<sub>min</sub> | |
| 8. |
In a two phase cylindrical rotor synchronous machine, the self inductances L , L for phases , respectively are __________ |
| A. | constant and equal |
| B. | constant and unequal |
| C. | varying and equal |
| D. | varying and unequal |
| Answer» B. constant and unequal | |
| 9. |
The following torque expression: Te=-isirMmaxsin r is applicable in a single phase cylindrical rotor synchronous machine when the rotor is __________ |
| A. | revolving |
| B. | stationary |
| C. | revolving or stationary |
| D. | none of the mentioned |
| Answer» D. none of the mentioned | |
| 10. |
In a single phase cylindrical rotor synchronous machine, the torque Te tends to ____________ the space angle r. |
| A. | reduce |
| B. | increase |
| C. | maintain constant |
| D. | all of the mentioned |
| Answer» B. increase | |
| 11. |
Which of the following equation best represents the mutual inductance between stator and rotor in a single phase cylindrical rotor synchronous machine? (where r= space angle between stator and rotor field axis) |
| A. | M<sub>sr</sub>=0 |
| B. | M<sub>sr</sub>=M<sub>max</sub> |
| C. | M<sub>sr</sub>=M<sub>max</sub>cos <sub>r</sub> |
| D. | M<sub>sr</sub>=M<sub>max</sub>sin <sub>r</sub> |
| Answer» D. M<sub>sr</sub>=M<sub>max</sub>sin <sub>r</sub> | |
| 12. |
Consider a single phase synchronous machine of cylindrical rotor type. A single phase supply is given to the stator winding, and a voltmeter is connected across rotor winding. For what value of r the voltmeter reads a zero? |
| A. | 0 |
| B. | 30 |
| C. | 45 |
| D. | 90 |
| Answer» E. | |
| 13. |
Consider a single phase synchronous machine of cylindrical rotor type. A single phase supply is given to the stator winding and a voltmeter is connected across rotor winding. For what value of r, the voltmeter reads maximum? |
| A. | 90 |
| B. | 0 |
| C. | 45 |
| D. | 30 |
| Answer» C. 45 | |