电机技术 电气电信 直流电源 外文翻译 外文文献 英文文献
21页1、电机技术(电机技术(Electric Motor Technology)Lessons In Electric Circuits,Volume II-ACBy Tony R.Kuphaldt Sixth Edition,last update March 07,2007Theory, Construction, And Requirements T The principles behind electric motors have been around for almost two centuries, but the technology has come a long way during the past few years. Although Michael Faraday first showed the relationship between current flow and magnetic fields in 1821,it wasnt until 11 years later that these principles were used to demonstr
2、ate the first electric motor. Actually, it was the invention of the commutator that allowed electromagnetic forces to be coaxed into rotary motion. Once electrical power could be turned into mechanical power, it was easy to show how the reverse was possible. In need of a source for his electric light,Thomas Edison proposed generating DC power to customers in 1882. Meanwhile, Nikola Tesla investigated brushless AC induction motors. By 1888, he was ready to oppose Edison by proposing the use of AC
3、 for power distribution. Despite some dirty campaign tactics by Edison,we all know how that contest turned out.Because of the importance of electric motors,I will spend some time this month examining their construction, theory,and whats required to use them. What began as a real distinction between DC and AC motors has become muddled due to the introduction of electronics to provide smart control. But lets start off with a simple look at electromagnetics.ELECTROMAGNETIC FORCEAt the center of our
4、 solar system,the sun goes through a sunspot cycle every 11 years. Sunspots are areas of intense magnetic fields that poke through the photosphere and are eventually drawn toward its attracting magnetic pole. When this collected opposition overpowers the suns dipole state,a flux reversal flips the dipole state. This is consistent with maximum sunspot activity and the 11-year cycle.The Earth has a record of flip-flopping magnetic poles, but the period is much longer. The last one occurred about 7
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