Практическая работа № 21 a.C.Electric motors.

Цель: Введение и активизация лексики по теме «Электрические моторы цепи переменного тока».

Оборудование: комплект тестов, раздаточный материал, иллюстрации по теме.

Vocabulary

I. Learn these words.

Alternating-current circuit

Single-phase

Polyphase

To be divided

Main

Stator

To set up

A rotating magnetic field

Rotor

цепь переменного тока

однофазный

многофазный

делиться на

главный

статор

создавать

переменное магнитное поле

ротор

Cooper bar медные штанги

A slot прорез, паз

A circumference окружность

A ring кольцо

To induce индуктировать, побуждать

A construction конструкция

An inverted alternator перевернутый альтернатор

To run работать

To supply снабжать, поставлять

A network система

II. Read the text. Translate and retell in Russian. A.C.Electric Motors.

Motors for alternating-current circuits may be either single phase or polyphase (two-orthree-phase). They may again be divided into two kinds, named respectively: I. Synchronous; II. Non-or asynchronous, ordinarily called induction motors.

The most widely used a.c.motor is the induction motor. It has two main parts: a) the stationary winding or stator, which sets up a rotating magnetic field, and b) the rotating part of the motor, i.e. the rotor. The rotor of a commercial a.c.motor consists of an iron core with large copper bars placed in slots around the circumferences and connected at both ends to copper rings. This is called a squirrel-cage rotor. When a rotor is placed in a rotating magnetic field, a large current is induced in it.

A.c. motors are exactly similar in construction to a.c. generators and may be called inverted alternators, since the same machine may be used as either a generator or a motor.

Synchronous motor are very suitable for large powers, where the machine can be started up without load, and once started run for long periods.

For supplying direct-current power networks, the supply comes first from an alternating-current source and is converted to direct current by synchronous convectors or motor generator sets.

III. Add necessary letter.

Pol-phase, sta-or, mag-etic, fi-ld, circum-erence, supp-y, ind-ce, net-ork.

IV. Finish the sentences.

1. Motors for alternating-current circuits may be…………..

2. The most widely used a.c. Motor is…………

3. The rotor of a commercial a.c.motor consists…………..

4. A.c. motors are…………

5. Synchronous motor are very……………..

V Learn the scheme of A.C. Electric Motors

A.C. Electric Motors

Single-phase Polyphase

Synchronous Asynchronous or Induction