1、 原文说明 原文说明的内容是：文章阐述了电机的工作原理、发展过程、以及伺服电机的工作控制原理。并且举例说明了伺服电机所适用的场合。 题名 Servomotors Elements and Applications 作者 NEWMARKER How Does a Motor Work? An electric motor converts electricity into mechanical motion. Electric motors are used in household appliances, electric fans, remote-controlled toys, and i
2、n thousands of other applications. The electric motor grew out of one of the earliest discoveries in electric science Aragos rotations. In 1824, Francois Arago discovered that a magnetic needle suspended over a copper disk would rotate when the disc was spun. The next year, computer pioneer Charles
3、Babbage and astronomer John Herschel showed that the action could be reversed: spinning a more powerful magnet above the copper disk would spin the copper disc. Then, in 1831, Michael Faraday conducted experiments that helped explain why this took place. While this laid the groundwork for the electr
4、ic motor, it was another half century before electric motors were doing useful work. Over the next few decades many inventors made improved devices for turning electricity into motion. One of these was Hippolyte Pixiis 1832 improvement called the commutator, which switched the flow of current betwee
5、n two or more sets of stationary electromagnets to keep a motor continuously rotating. Thomas Davenport was the first to build an electric motor large enough to be used in industry, and he was also the first to seek a patent on a motor. Soon electric motors were being used for such things as transpo
6、rtation. Moritz-Hermann De Jacobi used an electric motor on a boat on the Neva River, and Charles G. Page used one to build a small locomotive. After the appearance of commercial electric power systems in the 1880s, larger electric motors were possible. Edison encouraged the use of electric motors i
7、n industrial applications and designed several new electric motors for that purpose. An important change came in the later 1880s and 1890s, when electric power companies began considering the switch to alternating current. Alternating current was perfect for the distribution of electric power over l
8、ong distances, and it worked well with the Edison electric lamp, but no practical AC motor existed until the works of Galileo Ferraris in Italy and Nikola Tesla in the United States. Teslas contributions are remembered today more than Ferraris in part because Tesla was subsequently hired by the West
9、inghouse corporation, which used his patents along with many others to become one of the major producers of electric equipment. With a suitable AC motor available, AC power took off. It is still in use today. Servomotor Servomotors are available as AC or DC motors. Early servomotors were generally D
10、C motors because the only type of control for large currents was through SCRs for many years. As transistors became capable of controlling larger currents and switching the large currents at higher frequencies, the AC servomotor became used more often. Early servomotors were specifically designed fo
11、r servo amplifiers. Today a class of motors is designed for applications that may use a servo amplifier or a variable-frequency controller, which means that a motor may be used in a servo system in one application, and used in a variable-frequency drive in another application. Some companies also ca
12、ll any closed-loop system that does not use a stepper motor a servo system, so it is possible for a simple AC induction motor that is connected to a velocity controller to be called a servomotor. Some changes that must be made to any motor that is designed as a servomotor includes the ability to operate at a range of speeds without overheating, the ability to operate at zero speed and retain sufficient torque to hold a load in position, and the ability to operate at very low speeds for long periods of time without overheating. Older-type motors
