MCQOPTIONS
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MCQOPTIONS
This section includes 9 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. |
For obtaining maximum current when we conduct the Slip Test on a synchronous machine, its armature field will align along __________ |
| A. | d-axis |
| B. | q-axis |
| C. | 45 to d-axis |
| D. | 45 to q-axis |
| Answer» C. 45 to d-axis | |
| 2. |
for a synchronous motor, its power factor __________ |
| A. | improves with increase in excitation and may even become leading at higher excitations |
| B. | is independent of its excitation |
| C. | decreases with increase in excitation |
| D. | increases with loading for a given excitation |
| Answer» B. is independent of its excitation | |
| 3. |
While finding the parameters for an alternator, its voltage regulation is found to be negative. Then the load connected to it must be __________ |
| A. | capacitive nature |
| B. | inductive nature |
| C. | resistive nature |
| D. | can not be judged based on voltage regulation |
| Answer» B. inductive nature | |
| 4. |
For a 400 V, 3 phase alternator gives an open circuit voltage of 380V and armature current of 38A at a field current of 20A. Then the synchronous reactance of the machine is? |
| A. | 10 ohm |
| B. | 38/ 3 |
| C. | 19 ohm |
| D. | 1.9 ohm |
| Answer» B. 38/ 3 | |
| 5. |
Mark the correct expression for alternator working at a lagging power factor. |
| A. | tan = (IaXq Vtsin )/(Vtcos Ia*ra) |
| B. | tan = (IaXq + Vtsin )/(Vtcos Ia*ra) |
| C. | tan = (IaXq + Vtsin )/(Vtcos + Ia*ra) |
| D. | tan = (IaXq Vtsec )/(Vtcosec Ia*ra) |
| Answer» B. tan = (IaXq + Vtsin )/(Vtcos Ia*ra) | |
| 6. |
A salient pole synchronous generator has following per-unit parameter Xd = 1.2 pu, Xq = 0.8pu, ra = 0.25 ohms. Then the armature current at 0.8 lagging is? |
| A. | 1,-36.9 |
| B. | 1, 36.9 |
| C. | 1, 73 |
| D. | 1, 27 |
| Answer» B. 1, 36.9 | |
| 7. |
If the internal pf angle of a synchronous motor is 30 degree. Then the quadrature axis component of the armature is? |
| A. | 0.866 pu |
| B. | 0.5 pu |
| C. | 1.73 pu |
| D. | 0 |
| Answer» B. 0.5 pu | |
| 8. |
If the internal power factor angle of synchronous motor is 30 degree. Then the direct-axis component of the armature current will be __________ |
| A. | 0.5 pu |
| B. | 0.866 pu |
| C. | 1.73 pu |
| D. | 0 |
| Answer» B. 0.866 pu | |
| 9. |
In salient-pole machines, the armature mmf cannot be accounted for by introducing one equivalent reactance due to __________ |
| A. | non-uniform airgap |
| B. | variable resistance |
| C. | non-uniform air gap |
| D. | any of the mentioned |
| Answer» B. variable resistance | |