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Вариант 3 I. Переведите текст: Induction
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- 2021 год
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Фрагменты работ
I. Выберите из правого столбика слова и словосочетания, чтобы закончить предложения:
1. The induction motor is the most
commonly used a.c. motor. stator winding
2. The induction motor rotor is a
laminated cylinder.
3. The air gap between the rotor and
stator is kept very small to obtain
maximum field strength.
4. The current in the rotor circuit caused
by the induced emf sets up a magnetic field.
5. A rotating magnetic field is generated
when a.c. is applied to the stator winding.
II. Найдите многокомпонентные словосочетания и переведите предложения:
Вариант 3
I. Переведите текст:
Induction Motors
The induction motor is the most commonly used a.c. motor because of its simplicity, its robust construction and its low manufacturing cost. These characteristics of the induction motor are due to the fact the rotor is a self-contained unit which is not connected to the external source of voltage. The induction motor drives its name from the fact that a.c. currents are induced in the rotor circuit by the rotating magnetic field in the stator.
The stator construction of the induction motor and of the synchronous motor are almost identical, but their rotors are completely different. The induction motor rotor is a laminated cylinder with slots in its surface. The windings in these slots are one of two types. The most common is called a “squirrel-cage winding”, which is made up of copper or brass. No insulation is required between the core and the bars because of the very low voltage generated in the rotor bars. The air gap between the rotor and stator is kept very small so as to obtain maximum field strength.
The other type of winding contains coils placed in the rotor slots. The rotor is then called a “wound rotor”.
Regardless of type of rotor used, the basic principle of operation is the same. The rotating magnetic field generated in the stator induces an emf in the rotor. The current in the rotor circuit caused by this induced emf sets up a magnetic field. The two fields interact, and cause the rotor to turn.
When a.c. is applied to the stator windings, a rotating magnetic field is generated. This rotating field cuts the bars of the rotor and induces a current motors, this induced current will generate a magnetic field around the conductors of the rotor, which will try to line up with the stator field. However, since the stator field is rotating continuously, the rotor cannot line up with it, but must always follow along behind it.
As you know from Lenz’s Law, any induced current tries to oppose the changing field which induced it. In the case of an induction motor, the change is the motion of the stator field; so the force exerted on the rotor by the reaction between the rotor and the stator fields will set about trying to cancel out the continuous motion of the stator field. That is to say, the rotor will move in the same direction as the stator field, and will try to line up with it. In practice, it gets, as close to the moving stator field as its weight and its load will allow.
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