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electromagnet, electricity, generator, achievement, aluminium; electric motor, induction motor, galvanic battery, squirrel-cage motor, circular rings, parallel bars, a cylindrical cage, far-reaching innovation, speed change, the pole-amplitude of the machine, high-frequency engineering, wire cage.

2.9.2 Прочтите и переведите текст; расскажите о значениях слова «it» в соответствии с содержанием текста

1. The engine which could convert electric energy into mechanical power was already in existence. As early as 1822 Faraday outlined the way in which an electric motor could work: by placing a coil, or armature, between the poles of an electromagnet; when a current is made to flow through the coil the electromagnetic force causes itto rotate – the reverse principle, in fact, of the generator.

2. The Russian physicist, Jacobi built several electric motors during the middle decades of the XlXth century. Jacobi even succeeded in running a small, battery-powered electric boat on the Neva river in St. Petersburg. All of them, however, came to the conclusion that the electric motor was a rather uneconomical machine so long as galvanic batteries were the only source of electricity. It did not occur to them that motors and generators could be made interchangeable.

3. In 1888, Professor Galileo Ferraris in Turin and Nikola Tesla – the pioneer of high-frequency engineering–in America invented, independently and without knowing of each other's work, the induction motor. This machine, a most important but little recognized technical achievement, provides no less than two-thirds of all the motive power for the factories of the world, and much of modern industry could not do without it. Known under the name of "squirrel-cage motor" – because it resembles the wire cage in which squirrels used to be kept–ithas two circular rings made of copper or aluminium joined by a few dozen parallel bars of the same material, thus forming a cylindrical cage.

4. Although the induction motor has been improved a great deal and its power increased many times ever since its invention, there has never been any change of the underlying principle. One of its drawbacks was that its speed was constant and unchangeable.

5. Some years later a squirrel-cage motor with two-speeds – the most far-reaching innovation since the invention of the induction motor was developed. The speed change is achieved by modulating the poleamplitude of the maсhine.

Примечания

1. squirrel – белка

2. cage – клетка

Date: 2016-02-19; view: 1059; Нарушение авторских прав