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1. D. c. motors actuate installations requiring large starting torques. To them belong, for example, electrified transport (electric trains, trolleybuses, etc.), cranes and other installations. D. c. motors are also used in automatic control systems.

2. A d. c. motor consists of two main parts: stationary part (stator) and rotating part (rotor). These parts are separated by an air gap. The stator serves for producing the magnetic field. It includes the poles and a frame manufactured from iron and steel.

3. The rotor (armature) comprises a shaft, a core, a commutator and windings. The winding is made of coil sections consisting of insulated copper wire. The commutator includes copper bars insulated from one another. The bars are also insulated from the shaft. The commutator is attached to the shaft by means of metal rings. The armature connected to the load is actuated by a prime mover. The prime mover supplies a torque.

4. When a motor is operating at no-load, the armature current is equal to zero or so small that it can be ignored.

5. In direct connection of a d. c. motor to a supply circuit the starting current is rather heavy; it may exceed the rated value. This may result in fluctuations in the voltage or some other faults. In order to prevent these faults, d. c. motors should not be connected directly to the line voltage. In order to reduce high starting currents, starting rheostats should be utilized.

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2.11.4 Расскажите о конструкции двигателя постоянного тока, используя следующие глаголы: to consist of, to separate by, to include, to comprise, to make of, to insulate from, to attach to, to connect to, to actuate by

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