# Chapter 2 and 3

August 27, 2018 | Author: winston101386 | Category: Electric Generator, Mechanical Engineering, Magnetism, Components, Machines

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Chapter 2 Questions:

2-1. Distinguish between a generator and a motor? motor? A generator is an electromagnetic device that converts mechanical energy into rotating electrical mechanical force. A motor is just the opposite It converts mechanical energy to electrical energy.

2-2. What is an armature? A field? Armature is

the rotating part of a dynamo, consisting essentially of copper wire wound around an iron

core. Field is simply to create a magnetic field (magnetic flux) for the armature to interact with, thus

the field component can comprise either permanent magnets, or electromagnets formed by a conducting coil. 2-3. What two important requirements are necessary before generator action is possible? 2-4. What two important requirements are necessary before motor action is possible? 2-5. State Faraday’s law.

is a basic law of  electromagnetism   electromagnetism predicting how a magnetic a magnetic field will interact with an electric an electric circuit to produce an electromotive an electromotive force (EMF)—a phenomenon called electromagnetic called  electromagnetic induction. It induction. It is the fundamental operating principle of transformers, inductors, and many types of  electrical motors,  electrical motors, generators  generators and solenoids and solenoids 2-6. In what two ways is it possible to generate a higher voltage in a moving conductor? 2-7. how many lines of force must be cut per second if 1 volt v olt is to be generate in a moving conductor? 2-8. In an actual generator, what effect has the number of o f parallel paths in the armature winding upon the terminal voltage? 2-9. What effect has the number of armature paths upon the current -carrying ability of generator? 2-10. Is the power o utput of a generator affected by the number of parallel paths in the armature winding? Give reason for your answer. 2-11. Derive the fundamental voltage equation for t he dc generator. 2-12. Write the fundamental voltage equation as a function of the total number of armature conductors and the number of the armature-winding armature -winding circuits. 2-13. What two factors determine the direction of the generated voltage in a conductor moving through a magnetic field ? 2-14. Considering a DC generator, in what two ways can the polarity (plus and minus) of the brushes be changed?

2-15. Using the fictitious “rubber -ban” comparison, explain how the direction of the generated voltage may be determined. 2-16. State Lenz’s law. 2-17. Using lenz’s law, explain how the direction of the generated volt age may be determined. 2-18. What kind of current flows in the armature conductors of a DC generator? 2-19. What is alternating current? What is meant by the frequency of an alternating current? 2-20. What is commutator? Describe its co nstruction. 2-21. What factors determine the frequency of a generated alternating voltage? 2-22. Carefully describe the commutations process, using appropriate sketches t o illustrate your answer. 2-23. Why it is desirable to have m any coils of wire and commutator segments on the armature of a DC generator? 2-24. What kind of current is t heoretically delivered to a load by a DC generator? 2-25. What is meant by torque? 2-26. What factors determine the force exerted by a conductor on the armature of a Dc motor? 2-27. Will a force exerted by a conductor carrying a current when it is placed parallel to a magnetic field? Explain carefully. 2-28. What happens to the existing uniform field is a conductor carrying a current is place in this field? 2-29. Using s sketch showing a two-pole motor with a single coil placed with its two sides under the pole centers, describe how torque is develop by the coil. 2-30. Why is the torque develop by those conductors occupying positions in the inter-polar spaces of a motor?

Chapter 3 Questions:

3-2. Name the various parts of the dynamo and indicate which parts are stationary and which rotate. 3-4. What is meant by pole core? Pole shoe? 3-6. Why are laminations used in constructing the field cor e? 3-8. What two kinds of field winding are used for generators and motors? Describe the construction of each. 3-10. What is yoke? What purposes does it serve? How it is usually constructed? 3-12. Describe a commutator construction. 3-14. What is the function of the armature winding in a generator? In a motor? 3-16. What keeps the brushes in g ood contact with the commutator? 3-18. What purpose is served by the brush pigtails? 3-20. Name the two general types of armature winding. 3-22. In general, what is a frog-leg winding? 3-24. Explain what would happen if the coil span were 360 electrical degrees in a generator; in a motor. 3-26. What is the commutator pitch in the simplex-lamp winding? A duplex-lap winding? A multiplex-lap winding? 3-28. Under what condition is the ree ntrancy of a duplex-lap winding single? Double? 3-30. What is the purpose of multiplex-lap windings?

3-32. What general rule can be used to determine the number of parallel paths in a multiplex-lap winding? 3-34. Why must the ends of wave coils never be connected to the commutator exactly 360 electrical degree apart? 3-36. Explain why only two brush acts need be used in a machine in which the armature is wave wound. 3-38. How are the conductors in each path of a wave winding distributed around the armature? 3-40. under what conditions is it desirable to use as many brush acts as pole in machines having wave wound armature? 3-42. Under what circumstances would it be desirable to use multiplex-wave windings? 3-44. Why it is impossible to have circulating curre nt flowing in wave-wound armatures? 3-46. In tracing a simplex-wave winding once around the commutator, at what segment should one arrive with respect to the starting point? 3-48. Why it is usually more satisfactory to construct armature that have more commutator segments than slots? 3-50. What is meant by a double-element coil? a triple-element coil? When are they necessary? 3-52. what is meant by a “dead” or “Dummy” elements? 3-54. What purpose is served by a “dummy” elements? 3-56. Why are circulating currents detrimental to good operations? 3-58. what two important functions are served by equalizer connections in lap-wound armatures? 3-60. Exactly why does a frog-leg winding eliminate the necessity for using equalizer connections? Explain carefully. 3-62. What is the origin of the term frog-leg winding? 3-64. How many parallel paths are there in a p-pole frog-leg winding?

Chapter 2 Problem: 6

2-2. calculate the average voltage generated in a moving conductor if it cuts 2.5 x 10  maxwells in 1/40 sec.; in 1/80 sec. 2-4. the armature winding of the g enerator of problem 2-3 is modified so that it has two parallel paths instead of six. at what apeed should the m achine be driven if it is to develop the same voltage as before the change, assuming all other conditions to remain unchanged? 2-6. if the armature winding of prob. 2 -5 had four parallel paths, what would have been the generated voltage? 2-8. how may total conductors and conductors per slot w ould be necessary in the armature of prob. 2 -7 if the winding had four parallel paths? 2-10. what is the frequency of the alternating voltage generated in the armature conductors of (a) a sixpole 900-rpm machine? (b) and eight-pole 750-rpm machine? (c) a 10-pole 500-rpm machine? 2-12. at what speed is an armature machine rotating in a 12-pole m achine if the frequency in the armature conductor s is 50 cps? 2-14. what torque will the conductor of prob. 2-13 develop if it lies on an armature the diameter of which is 9 in.? 2-16. using the data of prob. 2-15, calculate the torque that will be developed if the flux density is reduced by 5 percent while the current is increased to 40 amp. 2-18. what must be the total armature-winding current in prob. 2-17 if the torque increases to 1,200 lbft while the flux density drops by 4 per cent?

Chapter 3 Problem:

3-2. how many parallel paths are there in the armature windings of prob. 3-1 if (a), (b) and (c) are simplex wave wound and the others are simplex-lap wound? 3-4. how many parallel paths are there in the windings of armatures that are wound (a) duplex-lap for six poles? (b) triplex-lap for six poles? (c) duplex-lap for eight poles (d) tr iplex-lap for 10 poles? (e) quadruplex – lap for six poles? 3-6. determine the degrees of reentrancy for the following lap windings : (a) duplex, 36 segments ; (b) duplex , 35 segments ; (c) triplex, 117 segments (d) triplex, 116 segments (e) quadruplex, 286 segments. 3-8. determine the commutator pitches yc for the following wavewound armatures :

(a) 75 segments,

four poles ; (b) 93 segments, four poles ; (c) 229 segments, six poles ; (d) 227 segments eight poles. 3-10. how many parallel paths are there in the following armature winding: (a) six-pole duplex-wave? (b) six-pole triplex-wave? (c) eight-pole simplex-wave? (d) eight-pole duplex-wave? (e) eifht-pole triplexwave? (f) eight-pole quadruplex-wave? 3-12. a commutator has a 456 segments. indicate whether or not the windings are possible: (a) simplexwave for six poles; (b) triplex-wave for six poles; (c) duplex-wave for eight poles; (d) simplex-wave for 10 poles. 3-14. for each of the answers of prob. 3-13, trace the winding around the commutator and show that the proper segment, ahead of or behind the first one, is reached.

3-16. will there be a “dead” element in each of the following combinations of slots and s egments: (a) 33 slots, 99 segments? (b) 76 slots, 227 segments? (c) 39 slots, 77 segments?(d) 54 slots 216 segments? 3-18. the emf generated in each conductor of a six-pole simplex-wave armature winding is 0 .48 volt. if the armature has 42 slots and 125 commutator segments, and there are four turns per armaturewinding element, calculate the terminal voltage of the generator. 3-20. a 54-slot 216-segment armature has a four-pole lap armature that is equalized 100 per cent at the commutator. (a) how many equalizer connections are there? (b) to what two segments is the first equalizer connected?

3-22. make a table for prob. 3-21 similar to that given for example 9 , p.80. 3-24. determine the coil and commutator pitches for a 72-slot 288-segment six-pole frog-leg armature winding.

Plates In

Direct current

Submitted by: Padogdog, Winston Submitted to: Eng’r. Claro, Charito

Date submitted: Dec. 12, 2014

Hindi mo ba alam. By:siakol Intro G,C 3x, D G C G C Hindi mo ba alam na ako'y nasasaktan G C D Sa tuwing ikaw ay aalis at hindi nag paalam Em Bm Em Bm Nais kong malaman mo na ako'y nag tatampo C Am D Pag nalimutan mo ang pasalubong ko (same chords) Hindi mo ba alam na ako'y nasasaktan Pag nakikita kitang may ibang ka kwentuhan Nais kong malaman mo na ako'y nandirito Pwede ba ako kahit maki usyoso Chorus C D Bm Em Ngunit pag sapit ng gabi heto ka sa 'king tabi Am D G G7 Sa pag ibig mo 'di ako nag sisisi C D Bm At pag gising sa umaga maamo mong Em mukha ang nakikita Am D G Na sa akin ay lubos na nagpa-paligaya. Guitar G, C 3x, D (same chords) Hindi mo ba alam na ako'y nasasaktan Sa tuwing ika'y na lulungkot at mata ay luhaan Nais kong malaman mo yan ay pupunasan ko Sa katapatan ng pagmamahal ko sa iyo. Repeat Chorus Solo part e|---------------------8-7--7--10-8-7--5--7-8--------------------------------|

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Chorus G Bm C G Ayos lang kahit pa nasasaktan ang puso ko Em Bm C D Kung sino pang minamahal sya pa ang ayaw sa 'yo G Bm C G Totoong problema ngingiti na lang ako Em Bm C D G Kung sino pang mina mahal s'ya pa ang ayaw sa 'yo Guitar G, C 4x same chords Nais kong mab beer house ngunit kulang ang pera Kayat nag kakape na lang dag-dag pa sa kaba Tutal wala naman akong dapat ika takot Dahil darating din ang araw syay aking malilimohot Tulay C

G

Am

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Kung di man sya makuha sa iba ay cha-chamba C G Am D Basta't ako'y bahala na malimot lang siya ha

Repeat 1st Stanza Repeat Chorus 2x