MCQOPTIONS
Saved Bookmarks
MCQOPTIONS
This section includes 309 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Machines knowledge and support exam preparation. Choose a topic below to get started.
| 301. |
Compare the per pole permeance of direct and quadrature of a salient pole synchronous machine |
| A. | Direct axis permeance is more than quadrature axis permeance |
| B. | Quadrature axis permeance is more than direct axis permeance |
| C. | Direct and quadrate axis permeances are equal |
| D. | Quadrature axis permanence is zero |
| Answer» B. Quadrature axis permeance is more than direct axis permeance | |
| 302. |
Synchronous generator voltage obtained by the synchronous impedance method is |
| A. | higher than actual as it does not account for magnetic saturation |
| B. | lower than actual as it does not account for magnetic saturation |
| C. | nearly accurate as it accounts for magnetic saturation |
| D. | nearly accurate as the generator is normally operated in the unsaturated regi on of magnetization |
| Answer» B. lower than actual as it does not account for magnetic saturation | |
| 303. |
Pole shoes of a salient pole synchronous machine are so shaped at that air-gap is least in the middle and increases somewhat towards the edges. This type of construction |
| A. | increases flux/pole for a given excitation. |
| B. | facilitates machining of pole shoes. |
| C. | eliminates a particular harmonic. |
| D. | reduces the harmonic content of the induced voltage wave. |
| Answer» E. | |
| 304. |
A synchronous generator is loaded and the armature current lags behind the excitation emf by angle . The electrical angle between the field axis and the axis of the armature reaction field will be |
| A. | 90 + |
| B. | 90 |
| C. | 90 |
| D. | |
| Answer» C. 90 | |
| 305. |
A synchronous motor is operated from a bus voltage of 1.0 pu and is drawing 1.0 pu zero power factor leading current. Its synchronous reactance is 0.5 pu. The excitation emf of the motor will be |
| A. | 2.0 |
| B. | 1.5 |
| C. | 1.0 |
| D. | 0.5 |
| Answer» C. 1.0 | |
| 306. |
A synchronous motor is running from busbars and has a torque angle of = 15 . The bus voltage and frequency are reduced by 10% while field current and load torque are held constant (all losses are negligible).The new torque angle will |
| A. | remain the same |
| B. | increase slightly |
| C. | decrease slightly |
| D. | the motor will lose synchronism |
| Answer» C. decrease slightly | |
| 307. |
Synchronous generator is operating at constant load while its excitation is adjusted to give unity pf current. If the excitation is now increased, the power factor will |
| A. | lead |
| B. | remain at unity |
| C. | lag |
| D. | become zero |
| Answer» D. become zero | |
| 308. |
Synchronous condenser means |
| A. | a synchronous motor with capacitor connected across startor terminal to improve |
| B. | a synchronous motor operating at full load with leading pf |
| C. | an over-excited synchronous motor partially supplying mechanical load, and also improving pf of the system to which it is connected |
| D. | an over-excited synchronous motor operating at no-load with leading pf used in large power stations for improvement of pf |
| Answer» E. | |
| 309. |
Fifth harmonic component of the induced voltage in 3-phase ac generator can be entirely eliminated by using a winding pitch of |
| A. | 2/3 |
| B. | 4/5 |
| C. | 5/6 |
| D. | 6/7 |
| Answer» C. 5/6 | |