3. Прочтите текст и выполните следующие за ним упражнения:

A.C. and D.C. Electrical Motors

1) Motors for alternating-current circuits may be single-phase or polyphase (two- or three-phase). They may again be divided into two kinds: 1) synchronous; 2) non- or asynchronous, ordinarily called induction motors.

2) The most widely used a. c. motor is an 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. When a rotor is placed in a rotating magnetic field, a large current is induced

in it.

3) A.c. motors are similar in construction to a.c. generators, that is why the same machine may be used as either a generator or a motor.

4) Synchronous motors are very suitable for large powers, where the machine can be started up without load, and once started can work for long periods.

5) The basic parts of a d. c. machine are the armature and electromagnets (or field coils). There are two electric circuits in the d. c. machine: the armature circuit and the excitation circuit.

6) A d. c. machine is reversible: if the machine is rotated and the magnetic field is excited the machine sends a direct current into the external circuit through the commutator and brushes: the machine operates as a generator. If the armature and excitation winding are joined to a d. c. circuit the armature runs and the machine operates as a motor and converts electrical energy into mechanical energy.

4. Переведите на русский язык в письменной форме абзацы 2,4,5,6.

5. Найдите соответствующие ответы на вопросы и напишите их в той последовательности, в которой заданы вопросы: Вопросы

1. What kinds are a.c. motors divided into?

2. What main parts does induction motor consist of?

3. How may a.c. motor be used?

4. What are the basic parts of d.c. motors?

5. What are synchronous motors suitable for?

Ответы

a. They are suitable for large powers where the machine can be started up without load, and once started can work for long periods.

b. It may be used as either a generator or a motor.

c. They are divided into synchronous and asynchronous (induction) motors.

d. It consists of the stationary winding or stator, which sets up a rotating magnetic field and the rotating part of the motor, i.e. the rotor.

e. the armature and electromagnets (or field coils).

6. Закончите предложения, выбрав соответствующий вариант окончания:

1. The most widely used a.c. motor is ... a) synchronous motor.

b) induction motor.

2. The basic parts of a d.c. machine are ... a) stator and rotor.

b) armature and field coil.

3. Motors for alternating current may be ... a) single-phase and polyphase.

b) only single-phase.

4. When a rotor is placed in a rotating magnetic field... a) it converts electrical energy into

mechanical energy.

b) a large current is induced in it.

Вариант 3