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AC Theory ch 30
Understanding How the DC Generator Works
| Question | Answer |
|---|---|
| 1. A generator is a device that converts ____ energy into ___ energy | mechanical electrical |
| 2. What happens when a conductor cuts magnetic flux lines? | Voltage is induced into the conductor |
| 3. DC generators operate on the principle of ___ | electromagnetic induction |
| 4. Explain, according to Flemings Generator Rule, the meaning of the extended digits. Label what each digit represents. | thumb = thrust pointer= point of field middle finger = current |
| 5. How much voltage is being produced when the rotating conductor is parallel to the magnetic flux lines? | zero |
| 6.Maximum voltage is induced into a conductor when it cuts the magnetic field at ___ degrees. | 90 degrees (? page 225 in text) |
| 7. ___ voltage is induced into the conductor when the loop is at 0degrees, 180, and 360 in relation to the field. | zero |
| 8. When a conductor loop is continuously rotated in a magnetic field, the ___ output voltage follows the ___ function | AC sine |
| 9. To convert the AC voltage from the armature to DC voltage, DC generators make use of a | commutator |
| 10. How does a commutator cause the AC voltage that is generated appear as a DC voltage output | cuts off half the AC wave |
| 11. When AC voltage is generated and then converted to DC voltage by use of a commutator, is the voltage a constant output? | No, it is pulsating |
| 12. The frequency of the pulsating DC output voltage of a generator is ____ that of an AC generator | twice |
| 13. What is the name of the rotating member of the DC generator | armature |
| 14. What three components make up the armature | iron core, commutator, windings |
| 15. What are the three types of armature windings found in generators. | lap wound, wave wound, and frog leg |
| 16. The wires connected to the brushes of a generator are designated ___ and ____ | A1, A2 |
| 17. ____ wound armatures are probably the most commonly used because they are designed for moderate voltages and moderate currents. | frog leg |
| 18. ___ wound armatures are used in machines designed for low voltage and high current. | lap |
| 19. ____ wound armatures are used in machines designed for high voltage and low current. | wave |
| 20. What are brushes made of and why | carbon based materials because they can deal with a lot of heat |
| 21. What is the function of pole pieces installed in the generator housing | To concentrate the magnetic field |
| 22. What is the physical relationship between the pole pieces and the field windings in the generator | pole pieces mounted on generator. field windings wound around pole |
| 23. Are permanent magnets ever used as the field poles in a generator | yes, they are used when the field is permanently mounted in stator |
| 24.What are the two types of connections for generator field windings | series and shunt |
| 25. The Series Field windings are made up of ___ (few/many) turns with large wire and the leads are labeled ___ and ____ | few, S1, S2 |
| 26. How is the Shunt Field connected in a generator? How are the leads tagged? | Paralell / F1, F2 |
| 27. The Shunt Field has a ___(high/low) resistance because it is made of ____ (large/small) wire | high, small |
| 28. When a load is connected to a series generator, the output voltage _____ | increases |
| 29. A series generator is ___ with residual magnetism | self excited |
| 30. As additional loads are connected to a series generator, the output voltage will continue to ___ until the iron in the pole pieces and armature becomes ____ | increase, saturated |
| 31. What three factors determine the level of the output voltage of a series generator | 1. strength of magnetic field produced by pole pieces. 2. number of turns of wire on the armature 3. speed of rotation or armature |
| 32. Based on your answers to the two previous questions, series generators would be best used with a (constant/varying) load | constant |
| 33. Self-excited shunt generators make use of __ to start the generation process | residual magnetism |
| 34. The shunt type of generator provides ____ output voltage before the load is applied | full |
| 35. As the load is increased on a shunt type generator, the output voltage will _____ | decrease |
| 36. To control the output of a shunt generator, a(n) ___ is installed to sense changes to the output current and to make adjustments to the shunt field current | electronic voltage regulator |
| 37. compound generators make use of a(n) ___ field winding and a(n) ____ field winding. | series shunt |
| 38. What is the primary advantage of a compound generator | overcome voltage problems |
| 39. A long shunt compound generator has the ___ in parallel with the ___ winding and the armature | shunt winding (into larger connection point) series |
| 40. The short shunt compound generator has the shunt field connected in parallel with the ___ | armature |
| 41. What is Cumulative Compounding | fields aid each other |
| 42. What is Differential Compounding | oppose each other |
| 43. In an Over-compound Generator, the load voltage is____(less than/equal to/ greater then) the no load voltage | greater |
| 44. In an Under-Compound Generator, the load voltage is ____(less than/equal to/ greater than) the no load voltage | less than |
| 45. In a Flat Compound Generator, the load voltage is ___(less than/equal to/ greater than) the no load voltage | equal to |
| 46. The greatest generator loss is due to the ___ of the windings | resistance |
| 47. Power loss due to induced currents in the core material of a generator is called ___ loss | eddie current |
| 48. ___ loss is due to molecular friction | hysteresis |
| 49. Almost all power losses in a generator, with the exception of flux linkage, are manifested in the form of ____ | heat |
| 50. The two primary magnetic flux fields in a generator are field flux and ___ flux | armature |
| 51. The magnetic neutral plane will shift in the direction of the ____. | armature rotation |
| 52. To prevent a shift in the neutral plane, ___ windings are installed in the generator to cancel the effects of self-induction in the armature. | interpole |
| 53. When DC generators are connected in parallel, an equalizing connection is used to connect the ___ fields of the two mahines in ___ with each orther | series, parallel |
| 54. What might happen if two DC generators are simply connected in parallel without an equalizer connection | generator will work against each other |
Created by:
JoshHampton