Circuit Breaker Abstract Essays - Electrical Wiring, Free Essays

Circuit Breaker Abstract Essays - Electrical Wiring, Free Essays Circuit Breaker Abstract A circuit breaker was examined to determine how it works. Basically, it is designed to disconnect the current if the current passing through the breaker is higher than the allowable current. Its main parts consist of a switch, connecting pads, and the disconnect device. Since the breaker consists of many individual parts, the only improvement found was to combine some of the parts into a single part. Introduction Our group dissected a thirty-amp household Circuit-breaker. Its purpose is to protect electrical appliances from being damaged though excessive currents. A circuit breaker limits the amount of current that may safely enter a household electrical system via a predetermined amperage rating. It is placed in series between your house and the provided electricity. Any current in excess of the rated current amount will trip the circuit breaker in to a non-conducting or open path condition. The closed path is maintained until either magnetism or thermal expansion causes the circuit to trip. Device Description The circuit breaker has several features that are worth noting in the design discussion. First is its ability to detect various types of loading situations. The breaker can not only open a circuit in response to a current spike, but can also react to a sustained moderate current draw, just above its rated current. The circuit breaker also has an easily resetable 3-position switch, and various internal safety features such as spark arrestors and cavity vents. Operation of the circuit breaker is simple, but utilizes complex mechanisms. Essentially there are to main internal mechanisms; the trigger and the switch. The trigger is the device that senses the abnormal current load. A sharp spike in current will cause a magnetic field to form in the trigger, releasing the switch. A slightly elevated, but more constant current draw through the breaker will cause the bi-metal composition of the trigger mechanism to deflect in an arc like manner, which is also capable of releasing the switch. This reaction may take a longer amount of time to open the circuit, but is designed to provide the user with a short time of extended current draw through the circuit before the breaker opens. The switch, which is activated internally by the trigger or externally by the user, simply opens or closes a set of contacts which complete the circuit. The switch can be set to open or closed from the outside of the breaker's case, but can only be set to the tripped position internally, as a results of the trigger mechanism. Once the breaker has been tripped internally, it must be reset externally by switching it off, and then back on. The features enable the breaker to do several jobs at once, eliminating the need for multiple elements in the circuit. For example, it provides the user with an easily assessable on/off switch, fault protection against current spike, and fault protection against heavy current draw. The design of the trigger mechanism allows one internal part to the job of two, as does the switch, which by design can be shut off either internally or externally. Some problems that come to light with these features include a limited service life and expensive manufacturing. Limited service life is a function of build quality. Many internal parts move without precise surface preparation or lubrication, indicating that repetitive motion could wear out the assemblies. Several internal springs may also wear out over time. And, because there are may small parts that fit integrally with each other, manufacturing costs may be inflated. Discussion It has been discussed that the circuit breaker has many good design points, such as double fault protection, a manually switchable mode, and built in safety features to prevent spark ignition and meltdown. And it seems that there aren't many undesirable features of the unit, possibly with the exception of cost. Because of the complexity of the inner workings, manufacturability is more difficult, thus raising costs. A small inspection was done to determine if any parts could be eliminated or combined to reduce the build cost, but no immediate solutions were identified. It appears that all attempts to improve or simplify the device have been implemented and maximized, leaving the only avenue for complexity reduction to be a change in application for the part. Conclusion A common household thirty amp circuit breaker was dissected in lab this week. It consisted of hard plastic, moving metal parts, and two springs (Figure 1). The circuit is placed in series between an electrical power source such as Georgia Power and the fuse box or beginning of a home's electrical system. The circuit breaker operates via two mechanisms. The circuit is

Understanging the Parallel Structure of English

Understanging the Parallel Structure of English One of the most common writing mistakes in more advanced English learners writing is parallel structure. Parallel structure refers to structures which are repeated because they are connected by words such as: and, but, and or. These connecting words are referred to as coordinating conjunctions. Here are a few examples of correct parallel structure. Tom enjoys taking hikes, riding his bicycle and paragliding in his free time.I went home, took a shower, changed my clothes and ate some lunch. Here are the same two sentences using incorrect parallel structure: Tom enjoys taking hikes, to ride his bicycle and paraglide in his free time.I went home, take a shower, change my clothes and eat some lunch. In both cases, there is a mistake in parallel structure. Notice how the verb forms in the correct version of the two sentences use the same verb form. In the incorrect version of the sentences, the verb forms are varied. Parallel structure refers to the same structure repeating throughout a sentence. In other words, if the gerund form (ing form) of a verb is used after one verb, all the listed verbs also take the gerund form. Remember:  If you are listing verbs after the main verb, keep the verbs in the same form. (verb infinitive, verb gerund) He hopes to play, eat and get some rest.She enjoys listening to music, reading novels and playing tennis.He would like to have some lunch, study and then play the piano. If you are conjugating a number of verbs to relate a story for the same subject, use the same tense. We went to church, bought some lunch, came home, ate and took a nap. There are also other types of parallel structure mistakes. Which two types of mistakes in the parallel structure do you think are made in these sentences? Bob drove carelessly, quickly and in a reckless manner.Peter mentioned that he wanted to go home, that he needed a shower, and go to sleep. ... and the correct versions of the sentences: Bob drove carelessly, quickly and recklessly.Peter mentioned that he wanted to  go home, that he needed a shower, and wanted to go to sleep. In the first sentence, adverbs are being used in a list and should continue, rather than injecting an adjective. carelessly, quickly, recklessly, ruthlessly, etc. RATHER THAN carelessly, quickly, and in a reckless (adjective) manner. In the second sentence, the dependent clauses are used that he wanted to go home... that he needed a shower, etc. and should continue in the same manner. Notice also that the verb used in the third clause of this string of clauses is in the present tense, rather than the past as the other clauses. Here is another example of a similar adjective mistake in parallel structure. Which adjective is incorrect? Why? Jennifer appears to be tired, distracted and upsetting. If you answered upsetting, you are correct. The first two adjectives tired and distracted refer to the state that affects Jennifer. In other words, she feels tired and distracted. Upsetting refers to the effect that she has on someone else. Jennifer is upsetting to Jim. In this case, the intent is that Jennifer appears tired, distracted AND upset. All three adjectives refer to how she feels, rather than the effect she has on someone else. Double-Check for Mistakes in Parallel Structure A good way to check for mistakes in the parallel structure is to look for anything you list using commas  and make sure the list of equal elements are all in the same form. Parallel Structure Exercise Identify and correct the mistakes in a parallel structure in the following sentences.   Alex decided to get up early, go jogging, eat a healthy breakfast and got ready for school.I wish he would listen to his father, take his advice, and applied for a job.James stopped smoking, drinking and to eat too much.Jason invited Tim, her, they and Peter to the wedding.He is an articulate, thoughtful, and meaningfully speaker.Alexander did her homework, cleaned her room, but doesnt play the piano.The politicians hope to clean up, and modernizing this city.Eating healthy food, drinking lots of water and get exercise improves your quality of life.The teachers had graded the tests, completed the reports and meeting with parents before they went on summer vacation.Sheila misses seeing Tom, going on long walks with her friends, and played football. Answers: Alex decided to get up early, go jogging, eat a healthy breakfast and  get  ready for school.I wish he would listen to his father, take his advice, and  apply  for a job.James stopped smoking, drinking and to  eating  too much.Jason invited Tim, her,  them  and Peter to the wedding.He is an articulate, thoughtful, and  meaningful  speaker.Alexander did her homework, cleaned her room, but  didnt  play the piano.The politicians hope to clean  up and  modernize  this city.Eating healthy food, drinking lots of water and  getting  exercise improves your quality of life.The teachers had graded the tests, completed the reports and  met  with parents before they went on summer vacation.Sheila misses seeing Tom, going on long walks with her friends, and  playing  football.